2 km FM transmitter

2 km FM transmitter

Description.
With a matching antenna, the FM transmitter circuit shown here can transmit signals up to a range of 2 kilo meters. The transistor Q1 and Q2 forms a classic high sensitive preamplifier stage. The audio signal to be transmitted is coupled to the base of Q1 through capacitor C2. R1, R3, R4, R6, R5 and R9 are the biasing resistors for the preamplifier stage comprising of Q1 and Q2. Transistor Q3 performs the collective job of oscillator, mixer and final power amplifier.C9 and L1 forms the tank circuit which is essential for creating oscillations. Inductor L2 couples the FM signal to the antenna.

Circuit diagram.

Notes.

• Assemble the circuit on a good quality PCB.
• The circuit can be powered from anything between 9 to 24V DC.
• Inductor L3 can be a VK220J type RFC.
• For L1 make 3 turns of 1mm enamelled copper wire on a 10mm diameter plastic former. On the same core make 2 turns of 1 mm enamelled copper wire close to L1 and that will be L2.
• Frequency can be adjusted by varying C9.
• R9 can be used to adjust the gain.
• For optimum performance, value of C8 must be also adjusted.
• Using a battery for powering the circuit will reduce noise.

                simple FM transmitter

Here, is a very interesting and simple project in the series of communication used to transmit noise free F.M. signal in the wide range up to 100 M using only one transistor. The transmitted message from F.M. transmitter circuit is received by the receiver having the facilities of F.M. channel or you can also try F.M. receiver circuit published in this website.

Circuit Description of simple F.M. transmitter

The entire circuit of F.M. transmitter is divided into three major stage i.e. oscillator, modulator and amplifier. The transmitting frequency of 88-108 MHz is generated by adjusting VC₁. The input voice given to microphone is changed into electric signal and is given to base of transistor T₁. Transistor T₁ is used as oscillator which oscillates the frequency of 88-108 MHz. The oscillated frequency is depended upon the value R₂, C₂, L₂ and L₃. This transmitted signal from F.M. transmitter is received and tuned by F.M. receiver.

PARTS LIST

Resistors (all ¼-watt, ± 5% Carbon)

R₁ = 180 KΩ

R₂ = 10 KΩ

R₃ = 15 KΩ

R₄ = 4.7 KΩ

Capacitors

C₁ = 10 KPF

C₂ = 10 PF

C₃ = 20 KPF

C₄ = 0.001 µF

C₅ = 1 µF/10V

C₆ = 4.7 PF

C₇ = 10 KPF

C₈ = 3.3 PF

VC₁ = 22 PF

Semiconductor

T₁ = BF194B

Miscellaneous

MIC₁ = Condenser mike

L₁, L₂ = 3 turns of 22 SWG wire around any thin pencil

L₃ = 2 turns of 22 SWG wire around any thin pencil.

Walky-talky without using inductor or coil

Walky-talky in this website is world 1st verified walky-talky project without using coil. Walky talky is very interesting and attain grabbing project for electronics hobbyist. Communication is done without any physical connection and mobile network up range of 500 meter. Almost all communication devices utilize coil which is burden for electronics hobbyist. So, we design this circuit without using any coil.

Circuit Descriptions of walky-talky

The entire circuit of walky-talky is divided into two main section transmitter and receiver section.
Transmitter section:- Transmitter section utilize  IC NE566 (IC₄) as VCO (Voltage Control Oscillator) for generating frequency about 30 KHz. Resistor R₂₄ with Capacitor C₂₄ used as frequency components for frequencies determination. Voice is pick-up by mike (MIC₁) and changed it into equivalent electrical signal. Signal from microphone is amplified by transistor T₄ and given to pin no 5 0f IC₄. NAND gate N₁ with crystal oscillator XT₄ finalizes the output from pin 3 of IC₃. Lastly, signal from NAND N₂ through N₃ and N₄ given to antenna for transmission.
Receiver section: - Transmitted signal from another walky-talky is received from same antenna which is used for transmission. Field effect transistor T₁ boosts the received signal and make more powerful and send to amplifier section made from transistor T₂ and T₃ with crystal oscillator XT₁ through XT₃. Detector section is made from diode D₁, Capacitor C₆ and resistor R₁₂. 30 KHz frequency is obtained from detector section.
Frequency of Phase Locked Loop IC NE565 (IC₁) is adjusted by capacitor C₉, resistor R₁₇ and variable resistor VR₁. Amplifier IC LM386 (IC₂) is used to amplify the signal and given to speaker.

PARTS LIST

Resistors (all ¼-watt, ± 5% Carbon)

R₁ = 47 KΩ

R₂ = 100 Ω

R₃, R₄, R₁₁, R₂₇ = 2.2 KΩ

R₅ = 330 KΩ

R₆, R₁₀ = 560 Ω

R₇ = 1 KΩ

R₈ = 220 KΩ

R₉ = 100 Ω

R₁₂, R₁₅, R₁₆ = 4.7 KΩ

R₁₃, R₃₁ = 10 KΩ

R₁₄ = 15 KΩ

R₁₇ = 1.8 KΩ

R₁₈ = 1.2 KΩ

R₁₉ = 1 KΩ

R₂₀ = 4.7 Ω

R₂₁, R₂₂ = 100 KΩ

R₂₃ = 120 KΩ

R₂₄ = 5.6 KΩ

R₂₅ = 22 KΩ

R₂₆ = 150 KΩ

R₂₈ = 330 Ω

R₂₉ = 220 KΩ

R₃₀ = 47 KΩ

VR₁ = 4.7 KΩ

VR₂ = 22 KΩ

Capacitors

C₁, C₆, C₁₀, C₂₄ = 1 KpF

C₂, C₄, C₅ = 47 KpF

C₃ = 20 KpF

C₇, C₉, C₂₃= 2.2 KpF

C₈ = 4.7 µF/16V

C₁₁ = 22 KpF

C₁₂, C₁₆ = 0.1 µF

C₁₃ = 2.2 µF/16 V

C₁₄, C₁₉, C₂₅, C₂₆ = 0.22 µF

C₁₅ = 10 µF/16V

C₁₇ = 220 µF/16V

C₁₈, C₂₀ = 10 KpF

C₂₁, C₂₂ = 68 pF

C₂₇ = 1000 µF/16V

C₂₈ = 10 µF/16V

Semiconductors

IC₁ = NE565 (Phase Lock IC)

IC₂ = LM386 (Amplifier IC)

IC₃ = CD4011 (Quad 2-input NAND Gate IC)

IC₄ = LM566 (Voltage Controlled Oscillator)

IC₅ = LM7812 (Voltage Regulator)

T₁ = BFW10

T₂, T₃ = BF194

T₄ = BC148

D₁ = 1N4148

Miscellaneous

XT₁ – XT₄ = 10.7 MHz crystal

SW₁ = Single pole double throw switch

LS₁ = 8Ω speaker

MIC₁ = Condenser microphone

Areal

Varying brightness AC lamp

Varying brightness AC lamp

In this circuit, an SCR is used to slowly vary the intensity of a 120 volt light bulb by controlling the time that the AC line voltage is applied to the lamp during each half cycle.

Caution:

The circuit is directly connected to the AC power line and should be placed inside an enclosure that will prevent direct contact with any of the components. To avoid electrical shock, do not touch any part of the circuit while it is connected to the AC power line. A 2K, 10 watt power resistor is used to drop the line voltage down to 9 volts DC. This resistor will dissipate about 7 watts and needs some ventilation.

Operation:

A couple NPN transistors are used to detect the beginning of each half cycle and trigger a delay timer which in turn triggers the SCR at the end of the delay time. The delay time is established by a current source which is controlled by a 4017 decade counter. The first count (pin 3) sets the current to a minimum which corresponds to about 7 milliseconds of delay, or most of the half cycle time so that the lamp is almost off. Full brightness is obtained on the sixth count (pin 1) which is not connected so that the current will be maximum and provide a minimum delay and trigger the SCR near the beginning of the cycle. The remaining 8 counts increment the brightness 4 steps up and 4 steps down between maximum and minimum. Each step up or down provides about twice or half the power, so that the intensity appears to change linearly. The brightness of each step can be adjusted with the 4 resistors (4.3K, 4.7K, 5.6K, 7.5K) connected to the counter outputs. The circuit has been built by Don Warkentien (WODEW) who suggsted adding a small 47uF capacitor from ground to the junction of the current source transistor (PNP) to reduce the digital stepping effect so the lamp will brighten and fade in a smoother fashion. The value of this capacitor will depend on the 4017 counting rate, a faster rate would require a smaller capacitor.

120 VAC Lamp Dimmer

120 VAC Lamp Dimmer

The full wave phase control circuit below was found in a RCA power circuits book from 1969. The load is placed in series with the AC line and the four diodes provide a full wave rectified voltage to the anode of a SCR. Two small signal transistors are connected in a switch configuration so that when the voltage on the 2.2uF capacitor reaches about 8 volts, the transistors will switch on and discharge the capacitor through the SCR gate causing it to begin conducting. The time delay from the beginning of each half cycle to the point where the SCR switches on is controlled by the 50K resistor which adjusts the time required for the 2uF capacitor to charge to 8 volts. As the resistance is reduced, the time is reduced and the SCR will conduct earlier during each half cycle which applies a greater average voltage across the load. With the resistance set to minimum the SCR will trigger when the voltage rises to about 40 volts or 15 degrees into the cycle. To compensate for component tollerances, the 15K resistor can be adjusted slightly so that the output voltage is near zero when the 50K pot is set to maximum. Increasing the 15K resistor will reduce the setting of the 50K pot for minimum output and visa versa. Be careful not to touch the circuit while it is connected to the AC line.

Lamp Flasher using NE 555

Flasher Circuit using NE 555

Description

This is the circuit diagram of lamp flasher operated from mains. By this you can flash up to 200 Watt lamps at rates determined by you. IC NE555 is wired as an astable multivibrator for producing the pulses for flashing the lamp. The flashing rate can be set by the value of resistors R2 & R3.

Diodes D1 & D2 provides a half wave rectified regulated supply for the IC. Transistor T1 is used to drive triac and triac BT136 for driving the load. Resistor R4 limits the base current of Q1.

Flashing Circuit Diagram & Parts List

Notes

• Assemble the circuit on a good quality PCB or common board.
• Connect a 100K pot instead of R2 if you need frequent changes in rate.
• Many parts of the circuit are live with potential shock hazards.So please be careful.
• As usual use an IC holder for mounting the IC.

        Modified Circuit

Hi Fi Amplifier circuit

Hi Fi Amplifier Circuit – 2X12 Watts

Description.

Here is the circuit of a 2X12 watt H iFi  amplifier circuit using IC TDA 2616 from Phillips.A quiet simple and robust circuit using very less components.This makes the circuit ideal for a portable power amplifier.The circuit delivers 12 Watts power on  8 Ohm speaker for each channel at +/- 12 V dual supply.

The TDA2616 is a  stereo power amplifier IC comes  in a 9-lead single-in-line (SIL9) plastic power package (SOT131). This IC is  specially designed for mains fed amplifier circuits, such as stereo radio,tape  and television .The IC has good gain balance of both channels and Hi-fi in accordance with IEC 268 and DIN 45500 standards.Also the IC TDA 2616 has special inbuilt circuit for the  suppression of noise signals at the inputs, during switch-on and switch-off.This prevents click sounds during power on and power off.

Hi Fi Amplifier Circuit Diagram with Parts List.

           

                                 Hi Fi Amplifier Circuit Diagram

Notes.

• All capacitors except C10 & C9 are ceramic.
• All capacitors must be rated 50V.
• Use a well regulated and filtered +/- 12 V dual power supply that is able to provide at least 2 A continuous current.

 

TDA 2616 Pin assignment & layout.

                  TDA 2616 PIN Diagram and Configuration

  

We have more Audio Circuits in our website, that you may like to read;
1. Low Cost Amplifier
2. 50 Watt Transistor Amplifier
3. 3 Band Graphic Equalizer
4. Sound Shifter Circuit
5. Speech Amplifier Circuit