Panel switch wiring

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.

 

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.

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.

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.

As the name indicates , a sample and hold schema is a schema which samples an input signal and holds onto its last sampled value until the input is sampled again. Sample and hold diagram are commonly used in analogue to digital converts, communication diagram, PWM diagram etc. The schema shown below is of a sample and hold schema based on uA 741 opamp , n-channel E MOSFET BS170 and few passive components.

As the name indicates , a sample and hold schema is a schema which samples an input signal and holds onto its last sampled value until the input is sampled again. Sample and hold diagram are commonly used in analogue to digital converts, communication diagram, PWM diagram etc. The schema shown below is of a sample and hold schema based on uA 741 opamp , n-channel E MOSFET BS170 and few passive components.

In the schema MOSFET BS170 (Q1) works as a switch while opamp uA741 is wired as a voltage follower. The signal to be sampled (Vin) is applied to the drain of MOSFET while the sample and hold control voltage (Vs) is applied to the source of the MOSFET. The source pin of the MOSFET is connected to the non inverting input of the opamp through the resistor R3. C1 which is a polyester capacitor serves as the charge storing device. Resistor R2 serves as the load resistor while preset R1 is used for adjusting the offset voltage.

During the positive half cycle of the Vs, the MOSFET is ON which acts like a closed switch and the capacitor C1 is charged by the Vin and the same voltage (Vin) appears at the output of the opamp. When Vs is zero MOSFET is switched off and the only discharge path for C1 is through the inverting input of the opamp. Since the input impedance of the opamp is too high the voltage Vin is retained and it appears at the output of the opamp.

This Simple Comparator Frequency LED Circuit Diagram uses a comparison frequency IC 74HCT00, the device enabling frequency pulses are compared. Frequency F1 (signal frequency channel 1) and F2 (signal frequency channel 2). If the two frequencies are equal, then LED lights.

This simple schema generates a good 1KHz sine wave adopting the inverted Wain bridge configuration (C1-R3 & C2-R4). It features a variable output, low distortion and low output impedance in order to obtain good overload capability. A small filament bulb ensures a stable long term output amplitude waveform. 

 Notes:

R1____________5K61/4W Resistor

R2____________1K81/4W Resistor

R3,R4________15K1/4W Resistors

R5__________500R1/2W Trimmer Cermet

R6__________330R1/4W Resistor

R7__________470RLinear Potentiometer

C1,C2________10nF63V Polyester Capacitors

C3__________100µF25V Electrolytic Capacitor

C4__________470nF63V Polyester Capacitor

Q1,Q2_______BC23825V 100mA NPN Transistors

LP1___________12V40mA Filament Lamp Bulb (See Notes)

J1__________Phono chassis Socket

SW1__________SPSTSlider Switch

B1_____________9VPP3

Clip for 9V PP3 Battery

This is a Simple Electromagnetic Ring Launcher Circuit Diagram. The electromagnetic ring launcher is comprised of.four sub diagram: a clock schema (built around U5, a 555 oscillator/timer configured for astable operation), a count-down/display schema (built around U3), a 74190 synchronous up/down counter with BCD outputs that is configured for countdown operation; 

U4, a ECG8368 BCD-to-7-segment latch/decoder/display driver; and DISP1, a common-cathode seven-segment display), a trigger schema (comprised of U6), an MOC3010 opto isolator/ coupler with Triac-driver output; TR1, an SK3665 200-PIV, 4-A Triac; and a few support components), and a reset schema (comprised of Ul, a 7400 quad 2-input NAND gate U2, a second 555 oscillator/timer configured for monostable operation; and a few support components). This schema is that of a repulsion coil (LI) used to demonstrate the principle of electromagnetic repulsion by propelling a metal ring around the core of LI through the air. A countdown schema is provided to count seconds before launch.

This is a protected Simple Intrinsically Safe Op Amp Circuit Diagram. The schema is designed to drive an external load. A fault condition in the external load schema could feed excessive current or voltage back into the line drive schema. If excessive voltage appears from the load, the two zener diodes will clamp that voltage to a safe level, which in this case is 10 V.

The current in the zener diodes, op amp, and the remainder of the schemary is limited to a safe level by resistors Rl, R2, and R3. D1 protects the op-amp output stage from 10 V appearing across the clamp diodes under a fault condition. The advantage of this schema is that, although it`s designed as unity gain buffer, the same techniques can be applied to inverting, noninverting, or differential gain stages.

How to Check if a Remote Control is Transmitting an Infrared Signal. Many households have 5 or 6 remote controls laying around the house. This is the simple Remote control tester schema diagram. When the remote control is not working, first check the battery before, It may be loss.If it is good,so detect transmit infrared light device.However, because the human eye can not see infrared light,so can not know how good or bad.But the photo transistor can use to detect infrared light. 

This schema so use this photo transistor is the light receiver from the remote control.If it is nice to have the bias current of the transistor BC558.It runs a current flows through the LED,so the LED bright.The remote control that works correctly. The variable resistor VR1 is used to adjust the sensitivity of the schema.

 

A beautiful diy gsm jammer or mobile cell phone jammer schematic diagram for use only in GSM1900 with frequency from 1930 MHz to 1990 MHz. The GSM1900 mobile phone network is used by USA, Canada and most of the countries in South America.

 

This cell phone jammier is not applicable for use in Europe, Middle East, nor Asia. The GSM jammier schema could block mobile phone signals which works on GSM1900 band, also called DCS. For more cell phone jammers check the related posts.

This is a fantastic schema for self-protection. In case a burglar intrudes your house, you can use this security schema as a weapon for self-protection by giving a mild electric shock to the attacker.

This schema comprises astable multivibrator, inverter, and voltage quadrupler sections. The astable multvibrator is designed for 1 kHz with a 9V DC supply. The inverter section consists of switching transistors and an inverter transformer. The primary of transformer is of 9V-0-9V and the secondary is of 100V, 100mA. For compatibility, a driver transformer that is used in radio is used as the inverter transformer. The secondary output current of 100 mA gives a good enough shock to human body.

The astable multivibrator consists of two BC107 transistors (T1 and T2), two 0.01µF capacitors (C1 and C2), two 4.7-kilo-ohm resistors (R1 and R4), and two 72-kilo-ohm resistors (R2 and R3). A squarewave output of 1 kHz (with a phase shift of 180 degrees) is obtained at the collector of transistor T1 or T2. This squarewave output is given to the base of switching transistors BD139 (T3 and T4).

The collectors of transistors T3 and T4 are connected to the primary of the transformer and their emitters are grounded. A DC supply of +9V is also applied to the center-tapping of transformer X1 through switch S1. This is an inverter action, so we get around 100V AC at the secondary of the transformer. This AC is given to a quadrupler schema consisting of capacitors C3 through C6 and diodes D1 through D4.

Fig. 2: Barrel of the toy gun with the arrangement

The voltage quadrupler develops a DC voltage output equal to three or four times the input AC voltage. During the first positive half cycle, diode D1 conducts, charging C1 to Vm with polarity as shown in Fig. 1. During the first negative half cycle, diode D2 conducts, charging C2 to 2Vm. During the second positive half cycle, diodes D1 and D3 conduct, charging capacitors C1 and C3, while the voltage across capacitor C2 charges capacitor C3 to the same value 2Vm. During the second negative half cycle, diodes D2 and D4 conduct and capacitor C3 charges C4 to 2Vm. Thus, the voltage across C2 is 2Vm, across C1 and C3 is 3Vm, and across C2 and C4 is 4Vm. Therefore we get around 350V at the output of voltage quadrupler (across points A and B, as shown in Fig. 1).

Press the pushbutton switch (S1) of the schema and touch the output connectors to any object. There will be a heavy electric discharge, which is enough for a good shock.

The schema assembly and testing procedure is as follows:

1. Use a can type +9V battery for Vcc.

2. The transformer (X1) is designed to have 9V-0-9V primary and 100V, 100mA secondary, with primary winding having 80 turns (40+40, i.e. centre tapping at 40th turn) of 26 or 27 SWG and secondary winding having 450 turns of 35 or 36 SWG.

3. Mount the schema in a toy gun with output connectors at the front end of the barrel. The output connectors may be connected to two aluminium pieces with an insulator placed between them to avoid short schema. The arrangement is shown in Fig. 2.

4. Press switch S1 (here the trigger point of toy gun) and touch the front end of the barrel of toy gun to a person. The current in the voltage quadrupler will get discharged through the metal or aluminium pieces via the human body and the person will feel the electric shock.

The schema (excluding toy gun) costs around Rs 90.

Caution. Check the schema thoroughly before testing on anyone and use it judiciously, only when necessary.

Sourced By: EFY Author:  Praveen Kumar

Below is a schematic diagram of a USB player.

This schema will allow you to connect any tape recorder that has a mic and remote input to a phone line and automatically record both sides of a conversation when ever the phone is in use. You will need to take a couple of voltage readings before connecting the schema. First determine the polarity of your phone line and connect it to the schema as shown and then determine the polarity of the remote input and connect it to the schema. Circuit operation is as follows. When the phone is on hook the voltage across the phone line is about 48volts dc. When the phone is off hook the voltage will drop to below 10volts dc. When the line voltage is at 48volts the FET is off which causes Q2 and Q3 to be off. When the phone is picked up the FET turns on along with Q2 and Q3 which turns your recorder on. The tape recorder must be in the record mode at all times. As you can see the power source for the schema is the phone line.

Noise is a serious environmental problem that affects us in our daily life. There is scientific evidence supporting that noise exposure can cause hearing loss, hypertension, heart disease, annoyance, sleep disturbance and decreased performance in schools. Sound-level indicators like the one presented here can help address this problem. This sound-level indicator monitors the sound level and indicates through an LED when the level is above the preset value.

Circuit and working
Fig. 1 shows the schema of noise-level alarm. The schema is built around three BC550 npn general-purpose transistors (T1 through T3), electret microphone (MIC1), two LEDs (LED1 and LED2) and a few other components.

Simple Noise-Level Alarm Circuit Diagram

The sound is captured by microphone MIC1 and amplified by first-stage high-gain transistor T1. Trimmer potentiometer VR1 is used to adjust the threshold level. the signal is amplified again with second-stage transistor T2. This amplified signal is rectified by diode D1 and the charge is stored in capacitor C10. Diode D1 should preferably be a small-signal Schottky diode such as BAT81, BAT82, BAT83, BAT85 or better. You can use 1N4148 and 1N914 also but the signal from the input should be stronger.

When the voltage across capacitor C10 is high enough, transistor T3 conducts and LED1 glows to indicate that the sound level is higher than the set level. LED2 indicates power supply is available to the schema.

Transistors T1, T2 and T3 should be high-gain type, such as BC550C, BC109C and BC108C. For powering the schema, you can use 6V from four AA-size batteries or 6V from a regulated wall adaptor.

Construction and testing
An actual-size, single-side PCB for the noise-level indicator is shown in Fig. 2 and its component layout in Fig. 3. After assembling the schema on a PCB, enclose it in a suitable case. Fix LED1, LED2 and potentiometer VR1 on the front panel.







After connecting the 6V power supply to the schema, set the desired threshold of sound and adjust VR1 to the point where LED1 starts glowing. For that, switch on radio or TV set and set its volume to a level where you want the warning to start. Now adjust potentiometer VR1 to the point where LED1 starts glowing.

To test the schema for proper functioning, check correct input supply at TP1 with respect to TP0. LED2 also indicates the same. LED1 glows when the sound level is above threshold, which can be simulated with a radio or music system.