Panel switch wiring

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:


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.

 

FM Modulator circuit is a simple FM modulation circuit using IC 555, where the resulting modulated signal has a tenuous meeting depends on the signal frequency information. 

The resulting signal can be spelled out quite nice and stable so that the result will be more perfect. No winding or inductor in series modulator, so you do not need to bother to make a winding and calculate the value of the coil that you created it. With this circuit the desired value of frequency modulation can be obtained easily by calculating the frequency of IC 555 in general, which is determined by the resistor 6.8 K and 3.3 K and 0.1 UF capacitor. To obtain the other frequencies of your stay replace one or all three components.

Actually fm modulator ic 555 circuit is very simple though, but I think it reliable enough to handle a simple application purposes that do not require a big power or a very high frequency. But if you want more power you can add the RF amplifier circuit at the output of this circuit. Thus, the results of modulated signal can be amplified with the help of a series of supporters. In accordance with my experimental series modulators can work well at frequencies below the MHz range, because it is not IC IC 555 which is devoted to support of a very high frequency. You can use oscilltor transistor circuit, XTAL or others if you need a very high frequency.

The difference circuit with IC 555 on the multivibrator circuit in general is the use of pin 5, on the FM Modulator circuit is pin 5 of IC 555 is used as input information signal, which in turn will influence the shape of the output signal (modulated). But in applying this 5 pin multivibrator functions normally associated with 0.01 UF capacitor or left alone.

A lot of FM transmitter circuits accept been already appear here. This just addition one, a simple two transistor FM transmitter. The aboriginal date of the circuit is a preamplifier date based on transistor Q1. This is a beneficiary to abject biased amplifier date area resistor R2 sets the beneficiary accepted and R1 provided the all-important beneficiary to abject bias. C1 is the ascribe DC decoupling capacitor which couples the ascribe audio arresting to the Q1 base. C8 is the ability accumulation by-pass capacitor.

Next date is the oscillator cum modulator date congenital about transistor Q2. Electrolytic capacitor C2 couples the achievement of the aboriginal date to the additional stage. R3 and R4 are the biasing resistors of Q2. R5 is the emitter resistor of Q2. Inductor L1 and trimmer capacitor C5 forms the catchbasin ambit which is all-important for creating oscillations. The articulate FM arresting is accessible at the beneficiary of Q2 and it is accompanying to the antenna application capacitor C9.

Notes.

• The circuit can be powered from anything between 6 to 12V DC.
• Using battery for powering the circuit will improve the performance and reduce noise.
• A 9V PP3 battery is a good option.
• If you are going with a battery eliminator, then it must be well filtered and regulated.
• Trimmer C5 can be used for adjusting the transmission frequency.
• Antenna can be a 1m copper wire.
• L1 can be constructed my making 4 turns of 1mm enameled copper wire on a 10mm diameter plastic former.
• Trimmer capacitor C6 can be adjusted for obtaining the maximum range.
• Most of the components required for this circuit can be procured from your junk box.