Wednesday, December 26, 2012

Sequential Turn Lights Driver Four LED left and right sequence Particularly suited to motorcycles

Sequential Turn Lights Driver Four-LED left and right sequence Particularly suited to motorcycles


R1_____________500K  1/2W Trimmer Cermet or Carbon
R2______________47K 1/4W Resistor
R3,R4____________1K 1/4W Resistors
R5,R6,R7,R8_____10K 1/4W Resistors

C1_______________1µF 63V Polyester or electrolytic capacitor
C2_____________220µF 25V Electrolytic capacitor

D1-D8__________LEDs Yellow ultra-bright types

Q1,Q2,Q3,Q4___BC337 45V 800mA NPN Transistors

IC1____________7555 or TS555CN or TLC555CP CMos Timer IC
IC2____________4017 Decade counter with 10 decoded outputs IC

SW1____________Vehicle Turn Lights switch (See Comments)

Battery_________12V Vehicle battery


This device was designed on request and allows sequential operation of four Leds either to left or right direction, obtained by means of a 7555 CMos timer IC (IC1) wired as an astable multivibrator driving a Decade counter (IC2). This IC is set to count a sequence of four by connection of pin #10 to pin #15, but any sequence count in the 2-10 range can be set by choosing the appropriate pin connection. Obviously, LEDs, Transistors and their respective Base-limiting resistors must also be added or omitted accordingly.
R1 is a variable resistor (Trimmer), used to set the desired speed of the LEDs. SW1 is a change-over switch that should already exist in your motorcycle, having a center-off position and Turn-left and Turn-right positions.
D1, D3, D5 and D7 are the Turn-left LEDs; D2, D4, D6 and D8 are the Turn-right LEDs.
For a motorcycle they are arranged on a single board about 20 - 25 cm wide as shown in the image below. The outer red LEDs are the tail/brake lights and can be driven by a circuit like the LED driven tail/brake Light Cluster available on this website.

Sequential Turn Lights example


  • The use of high brightness, high efficiency yellow LED types of suitable size is mandatory.
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7 Watt Audio Power Amplifier Circuit Schematic


This small amplifier is constructed around the TDA2003 IC, capable of delivering 4Wrms at 4ohms. The TDA 2003 has improved performance with the same pin configuration as the TDA 2002. The additional features of TDA 2002, very low number of external components, ease of assembly, space and cost saving, are maintained. The device provides a high output current capability (up to 3.5A) very low harmonic and cross-over distortion. Completely safe operation is guaranteed due to protection against DC and AC short circuit between all pins and ground, thermal over-range, load dump voltage surge up to 40V and fortuitous open ground. A conventional direct current can be connected as supply.

Circuit's picture:


Circuit diagram:

Circuit diagram


  • R1 = 470R
  • R2 = 47R
  • R3 = 100R
  • R4 = 1R
  • C1 = 1822pF
  • C2 = 100nF-63V
  • C3 = 100nF-63v
  • C4 = 10uF-25V
  • C5 = 470uF-25V
  • C6 = 1000uF-35v
  • C7 = 1000uF-35V
  • IC1 = TDA2003


  1. Music power output: 7W / 4ohm
  2. RMS output: 3.5W / 4ohm or 2W / 8ohm
  3. Total harmonic distortion: 0.05% (1W / 1kHz)
  4. Frequency response: 20Hz to 20kHz (-3dB)
  5. Signal/noise ratio: 86dB (A weighted)
  6. Input sensitivity: 40mV / 150Kohm
  7. Overload and short-circuit protected
  8. Supply voltage: 15V DC (8 to 18V DC possible) / 0.5A
  9. Dimensions: 2.2 x 1.4"
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Remote controlled switch circuit


Here is a versatile remote controlled  switch that can ON or OFF any appliance connected to it using a TV remote.

IR remote sensor IC TSOP 1738 is used for receiving the signal. Normally when no signal is falling on IC3 the output of it will be high. This makes Q1 OFF.When a signal of 38 KHz from the TV remote falls on the IC3 its output goes low.This makes Q1 conduct and a negative pulse is obtained at pin 2 of IC 1 NE 555. Due to this IC1 wired as a monostable multivibrator produces a 4 Sec long high signal at its out put.This high out put is the clock for IC 2 which is wired as a Flipflop and of , its two outputs pin 3
goes low and pin 2 goes high. The high output at pin 2 is amplified to drive the relay. For the next signal the outputs of IC2 toggles state.  Result, we get a relay toggling on each press on the remote. Any appliance connected to this circuit can be switched ON or OFF.

Remote Controlled Switch Circuit Diagram with Parts List .

Remote Control Switch Circuit
Remote Controlled Switch Circuit Diagram


* Before wiring the circuit make sure that the carrier frequency of the TV remote you have is 38 kHz.For that wire the sensor part only ,point your remote to the TSOP1738 and press any switch.If out put of TSOP1738 goes low then OK, your remote is of 38Khz type.Nothing to worry almost all TV remote are of this type.

* You can use any switch  of the remote because for any switch the code only changes, the carrier frequency remains same.We need this carrier frequency only.

* Assemble the circuit on a good quality PCB or common board.

* The appliance can be connected through NO or NC and C contacts of the relay .
* Use a regulated 6V power supply for the circuit.
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Sunday, December 16, 2012

AM Transmitter circuit

Here is the circuit diagram of a simple AM transmitter circuit that can transmit your audios to your backyard.This circuit is designed with limited  power output to match the FCC regulations and still produces enough amplitude modulation of voice in the medium wave band to satisfy your personal needs.You will love this!.
The circuit has two parts , an audio amplifier and a radio frequency oscillator. The oscillator is built around Q1 (BC109) and related components. The tank circuit with inductance L1 and capacitance VC1 is tunable in the range of 500kHz to 1600KHz. These components can be easily obtained from your old medium wave radio. Q1 is provided with regenerative feedback by connecting the base and collector of Q1 to opposite ends of the tank circuit. C2 ,the 1nF capacitance , couples signals from the base to the top of L1, and C4 the 100pF capacitance ensures that the oscillation is transfered from collector, to the emitter, and through the internal base emitter resistance of the transistor Q2 (BC 109) , back to the base again. The resistor R7 has a vital part in this circuit. It ensures that the oscillation will not be shunted to ground trough the very low value internal emitter resistance, re of Q1(BC 109), and also increases the input impedance such that the modulation signal will not be shunted to ground. Q2 is wired as a common emitter RF amplifier, C5 decouples the emitter resistance and unleashes full gain of this stage. The microphone can be electret condenser microphone and the amount of AM modulation can be adjusted by the 4.7 K variable resistanceR5.

Am Transmitter Circuit Diagram with Parts List.

Am Transmitter Circuit

Am Transmitter Circuit Diagram

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Wednesday, December 12, 2012

Wireless FM Transmitter

The wireless fm transmitter circuit described here has an extra RF power amplifier stage, after the oscillator stage, to raise the power output to 200-250 milliwatts. With a good matching 50-ohm ground plane antenna or multi-element Yagi antenna, this wireless fm transmitter can provide reasonably good signal strength up to a distance of about 2 kilometers.
The wireless transmitter circuit built around transistor T1 (BF494) is a basic low-power variable-frequency VHF oscillator. A varicose diode circuit is included to change the frequency of the fm transmitter and to provide frequency modulation by audio signals. The output of the oscillator is about 50 milliwatts. Transistor T2 (2N3866) forms a VHF-class A power amplifier. It boosts the oscillator signals’ power four to five times. Thus, 200-250 milliwatts of power is generated at the collector of transistor T2. FM wireless transmitter circuit diagram fm transmitter circuit diagram For better results, assemble the circuit on a good-quality glass epoxy board and house the transmitter inside an aluminium case. Shield the oscillator stage using an aluminium sheet. Coil winding details are given below:

  • L1 – 4 turns of 20 SWG wire close wound over 8mm diameter plastic former.
  • L2 – 2 turns of 24 SWG wire near top end of L1.
  • (Note: No core (i.e. air core) is used for the above coils)
  • L3 – 7 turns of 24 SWG wire close wound with 4mm diameter air core.
  • L4 – 7 turns of 24 SWG wire-wound on a ferrite bead (as choke)
Potentiometer VR1 is used to vary the fundamental frequency whereas potentiometer VR2 is used as power control. For hum-free operation, operate the wireless fm transmitter on a 12V rechargeable battery pack of 10 x 1.2-volt Ni-Cd cells. Transistor T2 must be mounted on a heat sink. Do not switch on the transmitter without a matching antenna. Adjust both trimmers (VC1 and VC2) for maximum transmission power. Adjust potentiometer VR1 to set the fundamental frequency near 100 MHz. This fm wireless transmitter should only be used for educational purposes. Regular transmission using such a transmitter without a licence is illegal in most countries
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Thursday, December 6, 2012

Battery eliminator circuit


Here is the circuit diagram of a battery eliminator circuit that can be used as a replacement for 9V PP3 batteries. The circuit given here can be used to power any device that operates from a 9V battery. The transformer T1 steps down the mains voltage and bridge D1 performs the job of rectification. Capacitor C1 is a filter. IC LM317T is the regulator here. The value of R1, R2 and R3 are so selected that the output voltage of IC1 will be steady 9 volts.

Circuit diagram.

battery eliminator circuit

  • Assemble the circuit on a good quality PCB.
  • Transformer T1 can be a 230V primary, 9V secondary, 1.5A step down transformer.
  • If 1A Bridge is not available, then make one using four 1N 4007 diodes.
  • Do not connect loads that consume more than 1.5A to this circuit.
  • A heat sink is recommended for IC1.
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