Friday, December 12, 2014

Electronic liquid detector circuit diagram



This electronic liquid detector circuit diagram is based on the ULN2429A monolithic bipolar integrated circuit designed for detecting the absence or presence of many different types of liquids. The ULN2429 electronic liquid detector circuit can be used in automotive , home or industrial applications . 
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Thursday, November 20, 2014

Doubler Digital Frequency

Doubler Digital Frequencycircuit includes a simple and easy to understand. Digital Frequency Doubler circuit application contained in the system electronics such as audio-producing organ, or keyboard. The function of this series Digital Frequency Doubler for multiplying two input frequencies. The process of multiplying 2 on scales in an organ in principle is like this series Digital Frequency Doubler. Example of rising to a ringing tone DO RE then electronically technique in it is by multiplying the two frequency bands such as this series Digital Frequency Doubler.


Doubler
Doubler Digital Frequency
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Wednesday, November 19, 2014

ADC 0804 Microcontroler Interface Engineering

In ADC 0804 interface techniques with microcontrollers are pin-pin control must be controlled if we want to use the ADC with the microcontroller, there is value addition refferensi voltage to be supplied in 0804 ADC interface with a microcontroller, for example, we use the 0804 ADC (8 bit), if we give refferensi voltage 2.55 volts then we will get the increase of 1 bit to change 10 mVolt. Please note that the 0804 ADC pin on the leg that is form Vref Vref / 2, so to get a 10mV resolution is necessary for setting Vref / 2 equal to 1.275 V

The interface circuit microcontroller with ADC 0804



Mechanical interface microcontroller with ADC 0804
The steps in accessing data from the ADC 0804 by the microcontroller sebgai follows;

Enable ADC with signal 0 at the foot of Chip Select.
Give commands from conversion by providing a low pulse to the foot of the ADC Write narrow
Wait for the ADC issued a signal 0 from his leg INT
Give a moment of time delay for data from the ADC is correct
Give the read command by giving the signal 0 at the foot of ADC Read
Give a moment of time delay Now data from the ADC is ready for use and if the microcontroller.
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Tuesday, November 18, 2014

Powerful Bat Detector device

PowerfulPowerful Bat Detector device Circuit Diagram

The Powerful Bat Detector is a abundance analysis blazon device. Abundance analysis blazon detectors acquiesce you to apprehend accelerated complete by digitally ascent the abundance bottomward into the animal audition range. For instance, a western pipistrelle bat emits accelerated complete in the ambit of 53 to 91 kHz. If you bisect that abundance by 16, the new abundance ambit is 3.3 to 5.7 kHz, calmly aural our audition range. Because the analysis is done digitally, all amplitude advice is lost. Accelerated sources candy by the detector catechumen to sounds like geiger-counter clicks and chirps.

The basal ambit of the Simple Bat Detector is apparent in the schematic diagram to the right. It is about composed of 3 chip circuits, or ICs. The arresting from an accelerated transducer is fed to IC-1, an LM386 audio amplifier, which is configured to accommodate a arresting accretion of 200. The arresting is accompanying to IC-2, a added LM386, by a .05 uf capacitor. IC-2 is configured to accommodate an added accretion of 20, for a absolute arrangement accretion of 4,000. The achievement of IC-2 is absolute accompanying to the ascribe of IC-3, a 7 date CMOS agenda affiliate circuit. The ascribe date of the affiliate acts as a aught bridge detector, triggering on the abrogating alteration of the arresting from IC-2. The bisect by 16 achievement is affiliated to a potentiometer, which serves as an audio akin control. A aerial impedance bowl earphone is affiliated to the achievement of the akin control. The 10K akin ascendancy is a baby printed ambit pot that is set and forgotten. The detector ambit is powered by a nine volt battery. ( The numbers abutting to the IC nodes accredit to the pin numbers of the ICs. Note the added pins listed at the basal of the schematic that charge to be angry to ground. )

A above advantage of a abundance analysis detector is that it is a advanced bandage accessory ... that agency it will let you apprehend all apparent bat sounds after the charge to tune the detector to any accurate frequency. Heterodyne detectors, which action accelerated complete in the analog domain, alone catechumen a baby ambit of frequencies at any accustomed time - you charge baddest which frequencies to accept to. If you tune up about 60 kHz to accept for a pipistrelle, you may not apprehend the big amber bats aerial nearby. The abundance analysis detector works in the agenda domain, converting the abounding spectrum of complete that the transducer is able to detect. So you get to accept to all of the accelerated sounds about you, after missing annihilation due to adverse affability choices. I feel this no-knobs-needed appropriate of the abundance analysis detector makes it a abundant best for the accidental bat observer, and student.

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Monday, November 17, 2014

Multiplexer Circuit With Logic Gate

Multiplexer circuit with a logic gate is a multiplexer circuit that utilizes a combination of logic gates.
Where the above example can be seen that the circuit has 2 bit selector and 4 input lines. You can make a circuit with more input channels by increasing the number of bits of the selector. And also you can use a combination of gates based on your own design with reference to the previous multiplexer truth table you should specify. So by making a truth table in advance you can easily create a series of logic gates.


Multiplexer

The working principle of the multiplexer circuit above is:

1. Value of bit 00 from the selector will choose the path of the first input as the output
2. Value of bit 01 of the selector will choose the path of the second input as output
3. Value of bit 10 of the selector selects the third input lines as output
4. Value of bit 11 of the selector will choose the four input channels as output
5. As long as there is no change in the bit selector logic condition of the output logic state also will not be amended.
6. If the line selector is connected with a series of counter-up the output to be obtained will represent the input lines in sequence.
7. So it can be concluded that the usefulness of the implementation of a multiplexer function is to satisfy the principle of a simple data distribution. Thus, with multiplexers is possible to transmit data remotely using only one connection.
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Saturday, November 15, 2014

100W MOSFET POWER AMPLIFIER

A 100W MOSFET power amplifier circuit based on IRFP240 and IRFP9240 MOSFETs is shown here. The amplifier operates from a +45/-45 V DC dual supply and can deliver 100 watt rms into an 8 ohm speaker and 160 watt rms into a 4 ohm speaker. This Hi-Fi amplifier circuit is suitable for a lot applications like general purpose amplifier, guitar amplifier, keyboard amplifier. The amplifier can be also used as a sub woofer amplifier but a subwoofer filter stage has to be added before the input stage. The amplifier has a low distortion of 0.1%, a damping factor greater than 200, input sensitivity of 1.2V and the bandwidth is from 4Hz to 4 KHz.

Circuit Diagram



About the Circuit

Capacitor C8 is the input DC decoupling capacitor which blocks DC voltage if any from the input source. IF unblocked, this DC voltage will alter the bias setting s of the succeeding stages. Resistor R20 limits the input current to Q1 C7 bypasses any high frequency noise from the input. Transistor Q1 and Q2 forms the input differential pair and the constant current source circuit built around Q9 and Q10 sources 1mA. Preset R1 is used for adjusting the voltage at the output of the amplifier. Resistors R3 and R2 sets the gain of the amplifier. The second differential stage is formed by transistors Q3 and Q6 while transistors Q4 and Q5 forms a current mirror which makes the second differential pair to drain an identical current. This is done in order to improve linearity and gain. Power amplification stage based on Q7 and Q8 which operates in the class AB mode. Preset R8 can be used for adjusting the quiescent current of the amplifier. The network comprising of capacitor C3 and resistor R19 improves high frequency stability and prevents the chance of oscillation. F1 and F2 are safety fuses.

Circuit Setup

Set R1 at midpoint before powering up and then adjust it slowly in order to get a minimum voltage (less than 50mV0 at the output. Next step is setting up the quiescent current and keep the preset R8 in minimum resistance and connect a multimeter across points marked X & Y in the circuit diagram. Now adjust R8 so that the multimeter reads 16.5mV which corresponds to 50mA quiescent current.

Notes

  • Assemble the circuit on a good quality PCB.
  • Use a +45/-45 V DC, 3A dual supply for powering the circuit.
  • Power supply voltage must not exceed +55/-55 V DC.
  • Before connecting the speaker, check the zero signal output voltage of the amplifier and in any case it should not be higher than 50mV. If it is higher than 50mV, check the circuit for any error. Replacing Q1, Q2 with another set could also solve the problem.
  • Fit Q7 and Q8 to a 2°C/W heat sink. Both Q7 and Q8 must be isolated from the heat sink using mica sheets. Heat sink mounting kits for almost all power transistors/ MOSFETs of almost all package styles are readily available in the market.
  • All resistors other than R10, R11 and R19 are 1/4 watt metal film resistors. R10 and R11 are 5W wire wound type while R19 is a 3W wire wound type.


Power Supply for the 100W MOSFET Power Amplifier


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Thursday, November 13, 2014

12V fixed voltage power supply circuit diagram

Here this circuit diagram is for +12V regulated (fixed voltage) DC power supply. These power supply circuit diagram is ideal for an average current requirement of  1Amp. This  circuit is based on IC LM7812. It is a 3-terminal (+ve) voltage regulator IC. It has short circuit  protection , thermal overload protection.  LM7812 IC is from LM78XX series. The LM78XX series IC is  positive voltage regulator IC for different voltage requirements, for example LM7805 IC is made for 5 volt fixed output voltage . There is LM79XX IC series for negative voltage .

Circuit diagram of 12V fixed voltage power supply


A transformer(Tx=Primary 230 Volt, Secondary 12 Volt , 1Amp step down transformer) is used to covert 230V to 12V from mains. Here used a bridge rectifier made by four  1N4007 or 1N4003 diode to convert AC to DC . The filtering capacitor 1000uF,25V is used to reduce the ripple and  get a smooth DC voltage. This circuit is very easy to build. For good performance input  voltage should be greater than 12Volt in pin-1 of IC LM7812. Use a heat sink to IC LM7812 for safeguarding it  from overheating.


12
Fig: 12V power supply circuit diagram
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Wednesday, November 12, 2014

ic NE 555 Timer IC Datasheet Applications and Circuit Schematics



NE-555 timer IC was being introduced around May 1971 by the Signetics Corporation, to become known as the NE-555 / SE-555, and was also the very first very mass-produced commercially produced timer IC available at that time. Philips semiconductor was then introduced this 555 timer in mid 1972. Its characteristics for versatility, stability, low cost, simplicity to produce long time delays in a variety of applications, make Electronic Engineers, Circuit Designers from mechanical timers, op amps, and various discrete circuits into the ever increasing ranks of timer users.

Invented by a clever Swiss man, Hans R. Camenzind in 1970, the NE-555 timer IC went on to become a legend in the industry. As we already know, the 555 timer operates in three basic mode: monostable (one shot), astable (oscilatory), and time delay. In the article below each of basic operating mode were described detailly in one sequence with its schematic diagrams.

Another sections you can follow in this datasheet applications are general design consideration of the 555 timer, frequently asked applications question (FAQ), design formulas, and sample of some ingenious applications. The sample of applications were presented such as Missing Pulse Detector, Pulse Width Modulation (PWM), Tone Burst Generator, Long Time Delays, Car Tachometer (click to enlarge the picture above), Auto Burglar Alarm, Cable Tester, Automobile Voltage Regulator, and more. Each sample is given with clear and detail circuit schematic diagrams.

The article is ended with Theory of Operation and The Speed Warning Circuit section. Read on complete information about The NE 555 Timer IC Datasheet Applications and Circuit Schematics with link to download in pdf document provided (source: doctronics.co.uk).

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Saturday, November 8, 2014

USB Power Booster

The USB serial bus can be configured for connecting several peripheral devices to a single PC. It is more complex than RS232, but faster and simpler for PC expansion.Since a PC can supply only a limited power to the external devices connected through its USB port, when too many devices are connected simultaneously, there is a possibility of power shortage. Therefore an external power source has to be added to power the external devices.
Circuit diagram:
USB Power Booster Circuit Diagram
In USB, two different types of connectors are used: type A and type  B. The circuit presented here is an add-on unit, designed to add more power to a USB supply line (type-A). When power signal from the PC (+5V) is received through socket A, LED1 glows, opto-diac IC1 conducts and TRIAC1 is triggered, resulting in availability of mains supply from the primary of transformer X1. Now transformer X1 delivers 12V at its secondary, which is rectified by a bridge rectifier comprising diodes D1 through D4 and filtered by capacitor C2.
 Pin configurations of moc3021, bt136 and 5v regulator 7805 
Regulator 7805 is used to stabilise the rectified DC. Capacitor C3 at the output of the regulator bypasses the ripples present in the rectified DC output. LED1 indicates the status of the USB power booster circuit. Assemble the circuit on a general-purpose PCB and enclose in a suitable cabinet. Bring out the +5V, ground and data points in the type-A socket. Connect the data cables as assigned in the circuit and the USB power booster is ready to function
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Friday, November 7, 2014

LM723 Variable Power Supply with Over Current Protection

The circuit design was intended to create an adjustable power supply over a range of 1.3V to 12.2V at 1A and be able to provide protection for over-current by utilizing LM723 regulator.


 Terminology
  • LM723 – a positive NPN standard voltage regulator mainly designed for series regulator applications which can be utilized for both foldback and linear current limiting due to its very low standby current drain circuit
  • Voltage Regulator – an electrical or electronic device created for the purpose of maintaining a constant voltage level of a power source within the suitable limits
  • 2N3055 – a complementary Silicon Epitaxial-Base planar NPN transistor mounted in Jedec TO-3 metal case for use as power transistor
Circuit Explanation
The integrated voltage regulator LM723 will supply 150 mA of output currents but any desired load current can be provided by adding external transistors for output currents in excess of 10A. This can be used as a linear or switching regulator since its output voltage can be adjusted from 2 Volts to 37 Volts while the input voltage can be at 40 Volts maximum. The range of variations of input voltage and load current can be kept at constant using this voltage regulator.

In this design, the DIL14 plastic packaged LM723 performs with 9.5V to 40V input DC voltage while having an output voltage that is not more then 6V to 7V below the input will lead to 150 mA current source from  the IC. The difference between the input and the output DC voltage plus the current is proportional to the amount power being dissipated by the transistor T1 as it accepts all the current brought by the load, thus requiring a heatsink with a heat conductive value of 5K/W. T1 is made from 2N3055 which is intended for series and shunt regulators, for output stages and high fidelity amplifiers, and for power switching circuits. The output stage of the integrated circuit will be less loaded when an external pass transistor is used which will conduct at emitter-follower mode. This will in turn cause T1 to conduct at base-emitter mode thereby producing a major resistance in the IC.

Both ceramic capacitors must be positioned closer to the integrated circuit to prevent undesired oscillations, which the LM723 is prone to, since ceramic capacitors have high frequency coefficient of dissipation. Having these capacitors directly soldered would be too much for the IC since the operating temperature of the IC is in the range of -55áµ’C to +125áµ’C

Application
Voltage regulators are used for several advantages in areas where uncontrolled voltage varies more than the accepted voltage of equipment which could be harmful and damaging. In motor vehicles, it matches the charging requirements of the battery and electrical load to the output voltage of the generator by rapidly switching from one to another of three circuit states using a dual pole switch loaded with spring. To keep a recommended range of voltage supplied to a consumer, regulators are used by alternating current distribution feeders or large scale power distributions or substations. This is useful in protecting the equipment using electricity by minimizing the variations in voltage.  The two types of regulators being used are step regulators where the current supply is controlled and the induction regulator where an induction motor adjust the voltage by supplying a secondary which smoothens the feeder line’s current variations.
The LM723 voltage regulators are widely used for wide range of applications such as a temperature controller, a current regulator, or a shunt regulator. Also, DC power supplies in electronic equipment are using voltage regulators.

Source:zen22142.zen.co.uk/Circuits/Power/723psu.htm
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Thursday, November 6, 2014

Off Line Telephone Tester Circuit Diagram

Here is a circuit of an off-line telephone tester which does not require any telephone line for testing a telephone instrument. The circuit is so simple that it can be easily assembled even by a novice having very little knowledge of electronics. A telephone line may be considered to be a source of some 50 volts DC with a source impedance of about 1 kilo-ohm. During ringing, in place of DC, an AC voltage of 70 to 80 volts (at 17 to 25 Hz) is present across the telephone line. When the subscriber lifts the handset, the same is sensed by the telephone exchange and the ringing AC voltage is disconnected and DC is reconnected to the Off Line Telephone Tester Circuit Diagram line. Lifting of the handset from the telephone cradle results in shunting of the line’s two wires by low impedance of the telephone instrument. As a result, 50V DC level drops to about 12 volts across the telephone instrument.

During conversation, the audio gets superimposed on this DC voltage. Since any DC supply can be used for testing a telephone instrument, the same is derived here from AC mains using step-down transformer X1. Middle point of the transformer’s secondary has been used as common for the two full-wave rectifiers—one comprising diodes D1 and D2 together with smoothing capacitor C1 and the other formed by diodes D3 and D4 along with filter capacitor C2. The former supplies about 12 volts for the telephone instrument through primary of transformer X2 which thus simulates a source impedance, and a choke which blocks AC audio signals present in the secondary of transformer X2. The AF signal available in secondary of X2 is sufficiently strong to directly drive a 32-ohm headset which is connected to the circuit through headphone socket SK1 via rotary switch S2. During ringing, a pulsating DC voltage from transformer X1 via rectifier diode D5, push-to-on switch S3, and contact ‘B’ of rotary switch S2 is applied across secondary of transformer X2.

The boosted voltage available across primary of transformer X2 is sufficient to drive the ringer in the telephone instrument. Please avoid pressing of switch S3 for more than a few seconds at a time to prevent damage to the circuit due to high voltage across primary of transformer X2. The circuit also incorporates a music IC (UM66) whose output is connected to secondary of transformer X2 via switch S2 after suitably boosting its output with the help of darlington transistor pair T1 and T2. This output can be used to test the audio section of any telephone instrument. After having assembled the circuit satisfactorily, the following procedure may be followed for testing a telephone instrument: 1. Connect the telephone to the terminals marked ‘To Telephone Under Test’and switch on mains (switch S1). 2. To test the ringer portion, flip switch S2 to position ‘B’ and press S3 for a moment. You should hear the ring in case the ringer circuit of the telephone under test is working. Please ensure that handset is on cradle during this test. 3. For testing the audio section, flip switch S1 to position ‘C’ and connect a headphone to socket SK1.

Pick the telephone handset and speak into its microphone. If audio section is working satisfactorily, you should be able to hear your speach via the headphone. If you dial a number, you should be able to hear the pulse clicks or pulse tone in the headphone, depending on whether the telephone under test is functioning in pulse or tone mode. If the telephone under test has a built-in musical hold facility, on pressing the ‘hold’ button you should be able to hear the music. Now flip switch S2 to position ‘A’. You should be able to hear music generated by IC1 through earpiece of the handset of the telephone under test, indicating propor functioning of the AF amplifier section. The circuit can be assembled on a small piece of veroboard. Try to mount the two transformers on opposite sides of the board, displaced by 90 degrees. Always keep handy multi-type modular plugs for testing various types of telephones. Mount all switches, sockets and LEDs on the front of testing panel
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Wednesday, November 5, 2014

Ultra Simple Microphone Preamplifier

This little project came about as a result of a design job for a client. One of the items needed was a mic preamp, and the project didnt warrant a design such as the P66 preamp, since it is intended for basic PA only. Since mic preamps are needed by people for all manner of projects, this little board may be just whats needed for interfacing a balanced microphone with PC sound cards or other gear. Unlike most of my boards, this one is double-sided. I normally avoid double-sided PCBs for projects because rework by those inexperienced in working with them will almost certainly damage the board beyond repair.

I consider this not to be an issue with this preamp, because it is so simple. It is extremely difficult to make a mistake because of the simplicity. As you can see, the board uses a PCB mounted XLR connector and pot, so is a complete mic preamp, ready to go. Feel free to ignore the terminals marked SW1 (centred between the two electrolytic supply caps), as they are specific to my clients needs and are not useful for most applications. The original use was to use them for a push-button switch that activated an audio switch via a PIC micro-controller. They are not shown on the schematic.

Ultra-Simple Microphone Preamplifier Image Project :
 P12-pic

The DC, GND and output terminals may be hard wired to the board, you may use PCB pins or a 10-way IDC (Insulation Displacement Connector) and ribbon cable. Power can be anything between +/-9V and +/-18V with an NE5532 opamp. The mic input is electronically balanced, and noise is quite low if you use the suggested opamp. Gain range is from about 12dB to 37dB as shown. It can be increased by reducing the value of R6, but this should not be necessary. Because anti-log pots are not available, the gain control is not especially linear, but unfortunately in this respect there is almost no alternative and the same problem occurs with all mic preamps using a similar variable gain control system.

Ultra-Simple Microphone Preamplifier Circuit diagram:

P12-f1

The circuit is quite conventional, and if 1% metal film resistors are used throughout it will have at least 40dB of common mode rejection with worst-case values. The input capacitors give a low frequency rolloff of -3dB at about 104Hz. If better low frequency response is required, these caps may be increased to 4.7uF or 10uF bipolar electrolytics. These will give response to well below 10Hz if you think youll ever need to go that low. The project PCB measures 77 x 24mm, and the mounting centers for the pot and XLR connector are spaced at 57mm. If preferred, a traditional chassis mounted female XLR can be used, and wired to the board with heavy tinned copper wire. The PCB pads for the connector are in the correct order for a female chassis mount socket mounted with the "Push" tab at the top.


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Tuesday, November 4, 2014

22Watt Car Subwoofer Amplifier

22W into 4 Ohm power amplifier, Variable Low Pass Frequency: 70 – 150Hz. This unit is intended to be connected to an existing car stereo amplifier, adding the often required extra "punch" to the music by driving a subwoofer. As very low frequencies are omnidirectional, a single amplifier is necessary to drive this dedicated loudspeaker. The power amplifier used is a good and cheap BTL (Bridge Tied Load) 13 pin IC made by Philips (now NXP Semiconductors) requiring a very low parts count and capable of delivering about 22W into a 4 Ohm load at the standard car battery voltage of 14.4V.

22 Watt Car Subwoofer Amplifier Circuit Diagram:


22
Parts:

P1_____________10K Log Potentiometer
P2_____________22K Dual gang Linear Potentiometer
R1,R4___________1K 1/4W Resistors
R2,R3,R5,R6____10K 1/4W Resistors
R7,R8_________100K 1/4W Resistors
R9,R10,R13_____47K 1/4W Resistors
R11,R12________15K 1/4W Resistors
R14,R15,R17____47K 1/4W Resistors
R16_____________6K8 1/4W Resistor
R18_____________1K5 1/4W Resistor
C1,C2,C3,C6_____4µ7 25V Electrolytic Capacitors
C4,C5__________68nF 63V Polyester Capacitors
C7_____________33nF 63V Polyester Capacitor
C8,C9_________220µF 25V Electrolytic Capacitors
C10___________470nF 63V Polyester Capacitor
C11___________100nF 63V Polyester Capacitor
C12__________2200µF 25V Electrolytic Capacitor
D1______________LED any color and type
Q1,Q2_________BC547 45V 100mA NPN Transistors
IC1___________TL072 Dual BIFET Op-Amp
IC2_________TDA1516BQ 24W BTL Car Radio Power Amplifier IC
SW1____________DPDT toggle or slide Switch
SW2____________SPST toggle or slide Switch capable of withstanding a current of at least 3A
J1,J2__________RCA audio input sockets
SPKR___________4 Ohm Woofer or two 8 Ohm Woofers wired in parallel

The stereo signals coming from the line outputs of the car radio amplifier are mixed at the input and, after the Level Control, the signal enters the buffer IC1A and can be phase reversed by means of SW1. This control can be useful to allow the subwoofer to be in phase with the loudspeakers of the existing car radio. Then, a 12dB/octave variable frequency Low Pass filter built around IC1B, Q1 and related components follows, allowing to adjust precisely the low pass frequency from 70 to 150Hz. Q2, R17 and C9 form a simple dc voltage stabilizer for the input and filter circuitry, useful to avoid positive rail interaction from the power amplifier to low level sections.

Notes:
  • IC2 must be mounted on a suitable finned heatsink
  • Due to the long time constant set by R17 and C9 in the dc voltage stabilizer, the whole amplifier will become fully operative about 15 - 30 sec. after switch-on.
Technical data:

Output power (1KHz sinewave):
22W RMS into 4 Ohms at 14.4V supply
Sensitivity:
250mV input for full output
Frequency response:
20Hz to 70Hz -3dB with the cursor of P2 fully rotated towards R12
20Hz to 150Hz -3dB with the cursor of P2 fully rotated towards R11
Total harmonic distortion:
17W RMS: 0.5% 22W RMS: 10%


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Monday, November 3, 2014

Simple FM Telephone Bug Circuit

Here is a simple transmitter that when connected to a phone line, will transmit anything on that line (execpt the dial tone) to any FM radio. The frequency can be tuned from 88 to about 94Mhz and the range is about 200 feet. It is extremely easy to build and is therefore a good, useful beginner project.

FM Telephone Bug Circuit Diagram:

Telephone

Parts:
R1 180 Ohm 1/4 W Resistor
R2 12K 1/4 W Resistor
C1 330pF Capacitor
C2 12pF Capacitor
C3 471pF Capacitor
C4 22pF Capacitor
Q1 2SA933 Transistor
D1, D2, D3, D4 1SS119 Silicon Diode
D5 Red LED
S1 SPDT Switch
L1 Tuning Coil
MISC Wire, Circuit Board

Notes :
 
1. L1 is 7 turns of 22 AWG wire wound on a 9/64 drill bit. You may need to experiment with the number of turns.
2. By stretching and compressing the coils of L1, you can change the frequency of the transmitter. The min frequency is about 88 Mhz, while the max frequency is around 94 Mhz.
3. The green wire from the phone line goes to IN1. The red wire from the phone line goes to IN2. The green wire from OUT1 goes to the phone(s), as well as the red wire from OUT2.
4. The antenna is a piece of thin (22 AWG) wire about 5 inches long.
5. All capacitors are rated for 250V or greater.
6. The transmitter is powered by the phone line and is on only when the phone is in use. S1 can be used to turn the transmitter off if it is not needed.
7. If you have problems with the LED burning out, then add a 300 ohm 1/4W resistor in series with it.



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Sunday, November 2, 2014

Low Power LED Flasher

It doesnt get much simpler than this circuit. Four components counting the battery!

How can an LED be illuminated by a 1.5V circuit, when the forward voltage of an LED is about 2V? The LM3909 uses the 100uF capacitor as a charge reservoir, building up a voltage of about 2V before discharging the cap through the LED.

This circuit is used in emergency flashlights on airplanes and in other public places. Though you may not have known it till now, the LM3909 is everywhere!

Low Power LED Flasher
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Saturday, November 1, 2014

Simple Multivibrator Flasher

Simple
The diagram basic 2 LED astable multivibrator flasher built by Mary. She chose to use 2 different colored LEDs and the red LED is clear when unlit. It is quite bright when lit compared to the yellow LED despite the fact that it only draws 0.5 mA more. The bread boarded test circuit was powered by a new 9 volt battery and was regulated by a L78L05 (in a TO-92 package as shown in the schematic). The 5 volt regulator was used to avoid exceeding the reverse breakdown voltage of the 2N3904. This topic will be discussed a little later on.

470 ohm current dropping resistors were chosen to keep the collector current draw less than 10 mA. The LEDS were bright enough to see well in dim lighting. You may change this resistor "R" value (lower R = brighter), but do not exceed the maximum current rating for the LED or transistor (this is more applicable to higher voltage multivibrators). You may also place 2 or more LEDs in series on each half of a multivibrator, however, the current dropping resistor may need to be reduced to maintain brightness. Consider using a power supply as opposed to battery power for your flashers.

To change the pulse (oscillation) frequency, you can change the base resistor or the timing capacitor values. For example, increasing the capacitor or the base resistor values will increase the time OFF per cycle and thus reduce the oscillation frequency. The oscillation frequency is 60 divided by the sum of the time OFF for each half of the multivibrator.  Do not feel you have to use the same timing capacitor for each 1/2 of the multivibrator. Multivibrators with different timing components on each 1/2 are termed asymmetrical.

Over time, some builders sent me emails that they could not get their multivibrator to run. I problem-solved with them and discovered many problems including bad parts, bread boarding errors, the oscillation frequency was too fast to observe, transistors were not saturated during their ON time and failure of the transistors due to excessive current or perhaps even reverse emitter-base breakdown.
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Friday, October 31, 2014

Voice Activated Home Automation

Voice recognition is no longer in infancy, especially since Siri just launched on the new iPhone 4S (although similar technology is available on Android too. This project shows you how to use it to automate your home without spending big bucks.




The core of this project is a VRBot speech recognition module.  Next, the project creator used some low-cost wireless light switches (you could also use relays).  The VRBot speech recognition module recognizes 32 custom voice commands.  Once a command is recognized, a wireless switch is activated via a radio receiver.  The setup is simple after you spend some time understanding the wireless communication protocol between the different modules.  See the project blog to engineer the whole thing yourself.
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Thursday, October 30, 2014

Speech Filter Circuit Diagram

In communications receivers and microphone amplifiers for transmitting equipment, there is frequently a need for a narrow, low-frequency band-pass filter that lets only the voice band through. This band is usually defined to be the portion of the audio frequency spectrum between approximately 300 Hz and 3300 Hz. In order to implement such a filter, we have calculated the values for two fifth-order Butterworth filters having these corner frequencies and connected them in series. The result is a band-pass filter for the desired pass-band with a skirt steepness of 100 dB/decade.  The first opamp (IC1) acts as a buffer.

Speech Filter Image :

 
image


The circuit can be powered by a unipolar supply voltage between 5 V and 18 V, which is a broad enough range that it should always be possible to find a suitable voltage when building the filter into existing equipment. The current consumption of the filter is only a few milliampères, which should rarely pose a problem. There is fairly wide selection of suitable candidates for the opamps, since the circuit is not critical in this regard. In addition to the indicated OP27A, you could consider using a TL081N or even an old-fashioned 741.

Speech Filter Circuit diagram : 
Speech-Filter-Circut-Diagram
Speech Filter Circuit Diagram 


Due to unavoidable spreads in component values, the pass-band curve of the filter will never be completely perfect in actual practice. However, the deviations will be very small and in any case inaudible. In the pass-band region, the gain is approximately unity. The printed circuit board design shown here allows the speech filter to be built in a very compact form, which can be an important factor if it must be fitted into existing equipment. You can quickly check the fully assembled circuit by momentarily measuring the voltages at the inputs and out-puts of the three opamps. Half of the supply voltage should be present at all of these locations.

PCB Layout :


Parts LIST:
Resistors:
R1.R2 = 22kΩ
R3,R11,R12,R18,R19 = 100kΩ
R4 = 470Ω
R5 = 150Ω
R6 = 10kΩ
R7 = 18kΩ
R8 = 15kΩ
R9 = 33kΩ
R10 = 82kΩ
R13-R17 = 3kΩ3
Capacitors:
C1,C8,C14,C15 = 100nF
C2 = 1µF MKT
C3-C7,C11 = 22nF
C9 = 33nF
C10 = 18nF
C12 = 10nF
C13 = 4nF7
C16,C17 = 10µF 16V
Semiconductors:
IC1,IC2,IC3 = OP27A, TL081CN
Miscellaneous:
Bt1 = 9-V battery



Author: G.Baars
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Wednesday, October 29, 2014

Solar Voltage Regulator

Our energy-hungry and environmentally aware society has been dawdling to put together moral depletion of the suns "on the house" power. But at once its to finish taking inedible. Using the suns stage at once, in lieu of cooking and other applications, is already a public and current knowledge stylish countries so as to hold good weather. angry-hose panels are in this day and age used in many parts of the the human race, in combination with a chatter or else thrilling powered fill with tears radiator to help old hat what time the weather doesnt help. But next to the same schedule, thrilling solar panels are still expensive, mitigating their use barely while a novelty, or else fashionable locations everywhere minute power is wanted, and bringing in infomercial power would ensue even added expensive.

A solar stimulating power usage needs panels in place of generation, batteries for cargo space, a control device to keep the batteries surrounded by a safe operating range, and in a little luggage a power converter for AC output. For folks who need to position up a hardly any panels meant for a summer lodge, a ferry, a remote peak installation, or else whatever, Im enclosed provided that a version of the controller circuit with the purpose of I engage in used popular a luck of such installations.

Such a solar panel regulator be supposed to make by slightest two operations: The obvious solitary is defensive the battery from overprice next to period of deep sun and diminutive consumption, and the other is defensive it from unnecessary discharge in bad weather conditions. Both cheat and deep discharge are injurious to a battery.

In place of regulating a solar panels output, in attendance are several achievable ways. A linear progression supervisory body can be real used, but has the disadvantage of causing more or less voltage discontinue and having some home power consumption by era whilst the sun is weak and the load is serious. Its much better to practice a shove supervisor, which is dormant on such epoch, and springs to life no more than while present is surplus energy. in lieu of this rationalize, largely solar panel regulators use the push scheme, the lone presented at this point being refusal exception.

But such force regulators roll up in the sphere of two flavors: Most mercantile units are ON-inedible regulators. to income, they hold a regular switch device, as a rule often a transistor otherwise MOSFET, at times even absolutely a relay, to facilitate stays rancid until the battery reaches done voltage, and followed by switches in, shorting off the panel until the battery voltage has dropped rancid. Then the bursting panel current is switched on again. The simply lead of this method is tos second-rate. The power switch operates with very low power dissipation, allowing a miniature, low cost construction.

But the disadvantages of this routine are key: The voltage output is all the epoch irregular linking in the region of 13 and 14.5V. The battery is cycling between getting charge too much and having to transfer all the load current, which strictly reduces the batterys time. And in the field of the event of battery disengagement otherwise failure, the gauge cycles quickly, applying pulses of broad panel voltage to the output, which can raze aware equipment powered by the classification!

The circuit presented at this time uses linear jolt supervision. Simply verbal, it burns rotten all surplus energy from the panel, keeping output voltage constant. next to epoch what time the solar panel output is equal otherwise greater than the load, and the battery is fully charged, the load gets its power from the panel, while the battery rests by the side of jam-packed charge. Five years battery time are entirely usual with this usage, while the same batteries stay fresh no more than two to three years what time used with pulsing regulators!

The next dependability of the valve is watching in excess of the battery voltage, and dropping rotten the load whilst the battery gets discharged too much. main batteries are harshly damaged by deep discharges, so its far preferable to plunge rotten the load, in that case to hold the battery stop working hip a bad weather spell. This controller is designed in support of 12V systems employing panels of up to 7A whole current, and many of not finished 20A. It can subsist certainly modified for greater currents.



U1A compares an bendable sample of the offer battery voltage to a 5V reference from a highly committed source. According to the findings, it controls the power transistors Q1 and Q2, which push inedible the overload power generation from the panel. A diode (D1) avoids battery voltage to operate back to the panel under rejection-light condition. To avert blurred voltage control due to unreliable diode globule, the sample is taken from the battery boundary, even if this course a very minor power devastate.

The power resistors R1 and R2 are dimensioned now such a way so as to under greatest shunting, these resistors command dissipate almost all power (with reference to 100W utter), leaving the transistors running cool. The highest dissipation in the transistors happens as soon as the control device is dissipating partly of the panel output; in this litigation, all transistor desire dissipate about 12W.

U1B is a Schmitt trigger to facilitate compares the battery voltage to the same firm reference of the other section, but in favor of an additional end: It controls the load switch Q3. This circuit resolve disconnect the load if the battery gets close to deep discharge, and reconnect it simply whilst renew is well underway. The unconstructive bank of the load is switched, simply as N-channel MOSFETs are much cheaper and better than P-channel ones.

Module annotations:

D1 can survive in the least diode with the purpose of can safely stay alive the panels current. If the panel has a very low voltage output (take away than 33 cells concerning cycle), it is an help to employ a Schottky diode in this place. Q1 and Q2 are conventional power Darlington transistors. They need to take place heatsinked meant for safe lengthy-call surgical treatment on the 12 Watt dissipation level. with the aim ofs trouble-free sufficient to act, but many newcomers misjudge how much thermal resistance is introduced by a mica insulator! map on 1K/W thermal resistance inside each one transistor, two epoch because much concerning the insulator (if you usage some), and 370K safe junction hotness. used for archetypal environmental conditions, this makes you need a heatsink having a thermal resistance of approaching 1.3K/W. If it is better, you induce new safety margin.

R1 and R2 want gain to be located made by combining a integer of power resistors concerning matching. no problem, you need to make up two resistor arrays of 4 Ohm, 80W all! This 80W dignitary includes a reasonable safety margin. These resistors long for give off a slice of part, and you may perhaps cook your coffee on them! transpire guaranteed to mount them in such a way with the aim of they have lots of ventilation, and that the heat from them will not contact the other components. R3 and R4 could to partake of be built from like combinations too, as of the low respect of merely 0.15 Ohm.

U2 is a voltage reference IC. You cannot exchange it by a standard Zener diode! Zeners are much too unstable! If you cant acquire this central processing unit locally, you could exhaust the ever-present 7805 manager as a substitute, but the power drain from the battery motivation stay upper. popular this project, of gush you dont need R8, but you would need a 1uF capacitor by the 7805 output. Q3 is a power MOSFET with the aim of has a very low Rds(on). You may well use a unusual lone, provided that it has a resistance to facilitates low an adequate amount of meant for your devotion. You could use several in equivalence. The individual I used has low loss even by the side of heaps of 20A, and can sell much added!

Calibration:

in the past the circuit is assembled, calibration is quite relaxed. unite the panel, leave the battery and load disconnected. With a pleasant sun on the panel, adjust RV1 designed for the desired voltage by the battery output. I advise 13.8V for sealed batteries, and 14 to 14.2V for uncluttered cell ones, to which wet can be alive added if vital.

instantly you need either a wavering power supply connected to the battery defenses, or else several kind of variable load. You may well in addition purpose your panel in the role of variable power supply, by sloping it away from the sun while a fixed load is connected to the battery position. The understanding is to adjust the voltage by the side of the battery ranks to the desired put down the lid-rancid evaluate (I put in a good word for 11.5V), and followed by move RV2 until Q3 shuts inedible, to the same degree indicated by a voltmeter across the load output, a 12V light bulb, before whatever you can use to detect it. similar to Q3 has go home for the day inedible, strengthen the voltage across the battery position and get by which level Q3 switches on again. This must occur on top of 12.6 and not more than 13.4 in opposition to. You may well enjoy to retouch RV2 and look on behalf of a compromise linking ON and rotten voltages. If your components are not too much revealed of regard, so therefore both potentiometers be supposed to have ended up rationally close to the base point.

Using additional panels:

You can handle this controller in support of bigger installations. Simply add lone band together like R1-Q1-R3 for both added 3.5A panel, and use a diode for D1 so as to handles the sum current. Remember that bulky diodes need high temperature sinks! U1A can drive by the side of slightest 8 such transistors. If you propose to build a really large arrangement, you might covet to add an emitter follower flanked by U1A and the power transistors. If you need to nickname large load currents, you can place to the same extent many MOSFETs wearing equivalent as you need. in attendance is rejection doable driving limitation in this basis.
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Tuesday, October 28, 2014

Cell Phone Detector circuit diagram

The circuit can detect both the incoming and outgoing calls, SMS and video transmission even if the mobile phone is kept in the silent mode. The moment the bug detects RF transmission signal from an activated mobile phone, it starts sounding a beep alarm and the LED blinks. The alarm continues until the signal transmission ceases.
An ordinary RF detector using tuned LC circuits is not suitable for detecting signals in the GHz frequency band used in mobile phones. The transmission frequency of mobile phones ranges from 0.9 to 3 GHz with a wavelength of 3.3 to 10 cm. So a circuit detecting gigahertz signals is required for a mobile bug.

Here the circuit uses a 0.22μF disk capacitor (C3) to capture the RF signals from the mobile phone. The lead length of the capacitor is fixed as 18 mm with a spacing of 8 mm between the leads to get the desired frequency. The disk capacitor along with the leads acts as a small gigahertz loop antenna to collect the RF signals from the mobile phone.
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Monday, October 27, 2014

600 Watt Quasi Amplifier With Mosfet IRFP460

Two versions of a robust module capable of delivering high powwer for extended periods.  The Actrk400 uses 6 n-channel Mosfets in the output stage to deliver around 400 watts into 4 ohms while the Actrk600 uses 12 n-channel Mosfets in the output stage to deliver power in excess of 600 watts into 4 ohms.  One constructor has achieved almost 900 watts with the Actrk600 layout using 12 IRFP460 Mosfets.

600 Watt Quasi Amplifier With Mosfet IRFP460

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Friday, October 24, 2014

Alarm Digital Clock

The circuit diagram on behalf of the digital watch. 2x16 LCD is connected to the docks 2 of AT89C51. P1.0 of uC force provide the SCL (entertainment in installments clock) and P1.1 SDA (serial data) for I2C message.

Nearby are four switches connected to the uC, having the status of given away within the think. Function of the keys are same as unmistakable from their names.

at what time the power supply is switched on it willpower confer you the default appointment and schedule, but anon you can convert it to the desired appraise. taking into account setting as soon as, the backup battery will keep the timepiece ticking even after the power is not near.

Alarm Digital Clock Schematic

A trivial a propos I2C:
There are basically four most important conditions wearing I2C protocol.
1) Start Condition
2)block Condition
3)Data Validity
4)Acknowledgement

1)Start Condition:
while SCL is sharp and SDA H->L, force take place taken since start condition meant for the exchange of ideas.
2)Stop Condition:
once SCL is high and SDA L->H, will generate a stop condition.
3)Data Validity:
after SCL is high at hand must be refusal chande voguish SDA line lone followed by the data is legally binding, the data loose change be supposed to be there made only as SCL is low.
4)Acknowledgement:
taking into account transfer of lone byte of data the reciever has to acknowledge the sender pro the winning reception. for this the sender add up to the SDA line soaring and reciever pulls down the SDA low, which tells the sender so as to data has reached safely.
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Thursday, October 23, 2014

12V Lead Acid Battery Charger

The follow-on charge voltage is something like 14.4V, which is fine on behalf of charging a gelled before AGM battery to full up charge, but is too high point in the same way as a seep mount, so dont leave this charger permanently connected to a battery. If you would like to make sure of truthful to facilitate, in that case add a subsequent diode in vogue string with D3! at hand is a LED connected as a charge indicator. It hope against hope light after the charge current is senior than a propos 150mA. The utmost charge current will ensue roughly 400mA. in attendance is an supplementary output, with the aim of provides about 20V on thumbs down load (depending on input voltage), and comes down for example the load increases. I incorporated this designed for charging 12V, 4Ah NiCd packs, which require precisely a restricted current but not a limited voltage for charging.

12V Lead Acid Battery Charger Circuit Schematic Diagram

document so as to if the charge output is abruptly-circuited, the overcurrent protection of U2 command kick arrived, but the current is still soprano an adequate amount of to impairment the diodes, if it lasts. So, dont short the output! If in its place you short the assisting output, the fuse be supposed to blow. I built this steed into a slight home-grown aluminum sheet corral, using dull-bug construction variety. Not very tidy, but it machinery. take notice of the elongated leads on the power resistors. They are needed, as with shorter leads the resistors long for unsolder themselves, to the same extent they contract pretty intense! The transistors and the control device IC are bolted to the indictment, which serves as stage sink. The transistors dont heat up very much, but the IC does.
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Sunday, October 19, 2014

LM2577 12V to 16V DC DC Converter

The circuit is a boost step-up regulator based around an LM2577-ADJ voltage regulator chip and a few other discrete components. Resistors R1 and R2 set the regulated output voltage.


A switch inside the voltage regulator closes between pins 4 and 3, causing current to flow through the inductor to ground. When the switch is released a few microseconds later, a back-EMF ‘kick’ is produced by the inductor, resulting in a positive pulse with respect to the input voltage. This pulse charges the output capacitor via the schottky diode, which tends towards an equilibrium voltage.
The switch continues to oscillate, the diode preventing the switch from shorting the output capacitor during the ‘on’ phase. The output voltage is monitored via the voltage divider R1/R2, causing the duty cycle of the switch oscillator to be continuously regulated in order to maintain a constant output voltage under varying loads.
Source: http://www.mcrent.com/workbench/dcdc1216/
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Saturday, October 18, 2014

Wurlitzer 680 Schematic


Wurlitzer 680 Schematic
Schematics for Wurlitzer 680
Wurlitzer Model 680 Amplifier Schematic
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Thursday, October 16, 2014

Build a Period To Voltage Converter Circuit Diagram

The input signal drives ICD. Because ICD`s positive input (V+) is slightly offset to + 0.1 V, its steady stateoutput will be around +13 V. This voltage is sent to ICC through D2, setting ICC`s output to +13 V. Therefore, point D is cut off by Dl, and CI is charged by the current source. Assuming the initial voltage on CI is zero, the maximum voltage (^Cinax) is given by: 

When the input goes from low to high, a narrow positive pulse is generated at point A. This pulse becomes -13 V at point B, which cuts off D2. ICC`s V+ voltage becomes zero. The charge on CI will be absorbed by ICC on in a short time. 

The time constant of C2 and R5 determines the discharge period— about 10 /is. ICB is a buffer whose gain is equal to (R& + R9)~Rg = lM5. ICD`s average voltage will be (1362f 1.545) + 2 = 1052/. RIO and C3 smooth the sawtooth waveform to a dc output.


Period-To-Voltage Converter Circuit Diagram

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Wednesday, October 15, 2014

Automatic Night Light Feeds Directly From the AC Line

There are many approaches to the problem of activating a light when it becomes dark, and a recent Design Idea covers this topic (Reference 1). Some approaches require a dc power supply and an electromechanical relay, but a better approach involves feeding the device directly from the ac line, minimizing the number of components 

(Figure 1).


Figure 1. The photoresistor activates the TRIAC and the load when darkness falls.

The heart of the device is a light-sensitive cadmium-sulphide resistor, PR, with a resistance of approximately 200 kΩ in the dark and decreasing to a few kilohms in the light. PR and capacitor C1 form an ac-voltage divider. In daylight, the voltage across PR is too low to generate the required gate-trigger current to turn on bidirectional ac switch Q1, thus keeping the load – usually a lamp – off. When it becomes dark, PR’s resistance rises, resulting in an increase in the TRIAC’s gate current that triggers the TRIAC and lights the lamp.

The circuit uses inexpensive, off-the-shelf components, including the VT90N1 photoresistor; a 0.1-μF, 275V capacitor; and an L2004F61 TRIAC with a load current of 4A rms, a peak blocking voltage of 200V, and a gate-trigger current of 5 mA. The exact specifications of these components are not critical; you could use others instead.

Editor’s note:
Attributes worth mentioning include the fact that the capacitor introduces a phase shift, which places the peak of the gate voltage close to the zero crossing of the load’s sine wave for optimum turn-on timing. Another benefit is thermal hysteresis, which occurs due to the reduction of the required triggering voltage and current as the TRIAC warms up after the initial turn-on. 
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Monday, October 13, 2014

LM35 Digital Remote Thermometer circuit and explanation

Digital Remote Thermometer circuit with very high accuracy temperature measurement features are set using the IC package numbers
Receiver Module Functional
LM35 (Linear temperature sensor IC) through a power amplifier and voltage change as a form of high frequency. To signal through the AC power cord.
For the receiver circuit and display module will receive the high frequency AC power cord and decode out to be the actual temperature figures with digital IC No. CD4553 Three-digit BCD Counter IC) and IC-CD4511 (BCD-to-7-Segment Latch / Decoder / Driver IC).
 Electronic Part List
Receiver Module
R1   100K 1/4W
C1,C2  47nF 400V
R2  1K 1/4W
C3,C7  1nF 63V
R3,R4,R6-R8  12K 1/4W
C4  10nF 63V
R5  47K 1/4W
C5,C6,C10  220nF 63V
R9-R15  470R 1/4W
C8  1000uF 25V
R16  680 1/4W
C9  100pF 63V
D1,D2,D5  1N4148
D3,D4  1N4002
D6-D8  Common-cathode 7-segment LED mini-displays
IC1  403
IC2   4518
IC3  78L12
IC4  4017
IC5  4553
IC6  4511
Q1 BC239C
Q2-Q4  BC327

L1  Primary (Connected to C1 & C2): 10 turns
Secondary: 100 turns
Wire diameter: 0.02mm. enameled
Plastic former with ferrite core. Outer diameter: 4mm.

T1 220V Primary, 12+12V Secondary 3VA Mains transforme
Remote Module Functional
    The frequency pulses from the wall and safely isolated by C1, C2 and L1 are amplified by Q1, diodes D1 and D2 of the peak limit his admission. The pulses are filtered by C5, IC1b square, divided by 10 in IC2B and sent for final countdown clock input of IC5. IC4 is the time base generator: it provides IC1b and reset pulses to the making and IC5 locks and opening time of IC5 at 1Hz frequency. It is powered by a 5Hz square wave obtained from the frequency 50Hz sector Retrieved from T1 secondary, squared and divided by 10 in IC1C IC2A. IC5 readers across the cathodes scenes Q2, Q3 and Q4 with a rate determined by frequency multiplexing C7. Readers also shows three anodes in parallel by the BCD to 7 segments decoder IC6. In summary, the input pulse power on, say, 2kHz frequency be divided by 10 and displayed as 20.0 ° C



Remote Circuit
Electronic Part List


Remote Module
R1,R3  100K 1/4W
C1  220nF 63V
R2  47R 1/4W
C2  10nF 63V
R4  5K 1/2W Trimmer Cermet
C3  1uF 63V
R5  12K 1/4W
C4,C6  1nF 63V
R6  10K 1/4W
C5  2n2 63V
R7  6K8 1/4W
C7,C8  47nF 400V
R8,R9  1K 1/4W
C9  1000uF 25V
D1  1N4148
IC1  LM35
D2,D3  1N4002
IC2  LM331
D4   Red LED
IC3  78L06
Q1  BC238
Q2 BD139

L1   Primary (Connected to Q2 Collector): 100 turns
Secondary: 10 turns
Wire diameter: 0.02mm. enameled
Plastic former with ferrite core. Outer diameter: 4mm.

T1   220V Primary, 12+12V Secondary 3VA Mains transformer
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Sunday, October 5, 2014

5 to 15V 400mA Regulated Power Supply

5 to 15V 400mA Regulated Power Supply

This project is a simple DC regulated power supply that has a variable DC voltage range from 5V to 15V. It can supply current up to a 400mA to power the various circuits for your electronic projects. The voltage output is varied by using the potentiometer VR1. In this circuit, the input line power supply is designed for 240VAC. If 110VAC input is used, change the ratings of the varistor to 150VAC and the transformer ratio to 110V/12V.

Fuse F1 is used as a protection in case there is any short circuit in the circuit. Varistor V1 is connected in parallel to the input of the line voltage to clamp the surge voltage from the line to a reasonable level that helps to protect the transformer and other circuitry. Once the voltage level surge to a high level beyond the ability of the varistor to absorb it, fuse F1 or varistor V1 or both will burn. If this circuit failed after a period of operation, check that the fuse and the varistor are still in good condition or else replace them.

Diodes D1, D2, D3 and D4 are used to rectify the 12VAC voltage to DC voltage. Electrolytic capacitor E1 is used as a smoothing capacitor to reduce the ripple of the DC voltage. The DC voltage is fed into the input of 7805 regulator where the output DC voltage is obtained. Changing the value of VR1 will change the output of the DC voltage. Capacitor C1 is used to filter out high frequency component from the power supply.
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Friday, October 3, 2014

FM Radio Using TDA7000

Here’s a design simple circuit using TDA7000 that can build an FM radio with a minimum of components; most of them so easy to manage, like the ceramic capacitors that do not require polarization and only two resistors. Here’s the figure of the circuit;


The components you will employ will be of small dimensions and low cost. Even the integrated circuit itself, the TDA 7000, is not of great cost.
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Thursday, October 2, 2014

Temperature Data Logger 4 Channel Four Channel

Heres a temperature data logger circuit, an 8-pin microcontroller based circuit for temperature data logging via the serial port of any computer from between 1 and 4 remote digital temperature sensors, DS1820/DS18S20 made by Dallas.

Features of the Temperature Data Logger are are follow:
  • Provides realtime data via the serial port.
  • Interfaces up to 4 x DS1820 sensors.
  • Accuracy to 0.5 degrees centigrade
  • Fahrenheit scale selected by a jumper
  • No external power required
  • Data stream easily logged & processed.
  • Over 200m distance for each sensor


The sensors of temperature data logger may be located more than 200 yards from the PCB. Just check that the remote VDD is above 4.4Volts. Its recommends 10uF tantalum capacitors be placed across the power supply pins (not supplied) to minimise random errors and possibly get increased range.


Download :
- Circuit Schematic and Parts List
- Sensor Specs DS1820 DS18S20
- Software for Windows and DOS
- Source Code
- Terminal Emulator 
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Wednesday, October 1, 2014

Stereo Cassette Player Circuit Diagram

As the equipment is mains operated, the battery compartment can be removed. The loudspeaker can also be removed as it is no longer required; the mains transformer may be fitted in its position. lf so desired, you · may add a neon indicator and a mains switch as well. Assembly cost and time As to the cost, you are lucky if you are in Delhi and can shop around Lajpatrai Market. The cost would be around Rs 400 or even less if you know the way the Delhi market works. Outside Delhi, the cost would be around Rs 450 much less than you would pay for a mono cassette recorder. lt is certainly worth every rupee that you spend as it would enable you to use the stereo system that you already own. Assembly time would depend on your familiarity with the electronic circuitry, but it would be a weekend well spent. (Time you need for shopping for the mechanism and parts would be extra.)  Two direct·coupled transistors are used in the preamplifier, with base bias for the first provided from the emitter of the second. This system of biasing results in heavy DC ° feedback that ensures stable operation of the circuit.


With the DC operating conditions stabilised, as mentioned, the AC characteristics of the preamplifier are also stabilised. The AC feedback from the collector of the second A transistor to the emitter of the first mainly provides frequency equalisation high frequency de-emphasis to compensate for the recording characteristics. To keep up a high signal- to-noise ratio in the high frequency range, the highs are boosted during recording. (This is called pre-emphasis.) A reverse treatment is therefore essential in playback to reproduce the original high-frequency signal correctly. An R- C combination, 22k with 5nF capacitor, carries out this function adequately.

Output from the preamplifier is fed to a 741 op-amp set for a gain of about ten. The total gain is thus around 1000 so as to provide a 100mV signal from 100uV input normally expected from a cassette head. Use of discrete preamplifier at the input ensures a good signal-to-noise ratio, and the op-amp at the output with a wide dynamic range ensures that there is no chance of signal being driven into saturation. The signal from the preamp is fed to inverting terminal number 2 of the op-amp through 5.6k resistor. Negative feedback from the output terminal number 6 through 68k is also provided to terminal number 2. The non-inverting terminal number 3 is set to half the supply voltage. That sets the DC voltage at terminal number 6. Thus an optimum swing of the output is possible at terminal number6. Positive supply terminal number 7 is taken to the supply positive, and terminal number 4 returned to ground. The output from the op-amp is taken out through a47k resistor to the standard 3.5 mm socket used in cassette recorders. The socket fits in a window provided in a ‘Sony’ cabinet for mono cassette recorder. `  
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