7 / 15 watt FM Transmitter PLL stereo digital circuit

A very high quality stereo FM transmitter circuit , thoroughly time tested ,highly reliable, crystal controlled PLL based for zero  frequency drift is reviewed below. The main circuit uses a very popular IC -KT0803L ,to develop two channel stereo audio modulated FM signal from76 MHz to 108 MHz covering the FM band of  88 MHz to 107 MHz feeding  to 3 stage buffering before being fed to the final power amplifier using most commonly used 2SC1971 for 7 watt or MOSFET -RD15HVF1 for 15 watt. But unfortunately most commercially available 2SC1971 or  RD15HVF1 are duplicate. Thus if one ventures trying any circuit with this power Transistor/ MOFET usually are unsuccessful. So I strongly recommend to go for readymade units. Aux audio is directly fed at pin 6 & 7 while for mic input it is amplified by LM358 and then…

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Phase angle control using Arduino

Submitted below ac load management by delayed phase angle triggering to opto-coupler(U3)¬† interfaced triac (U4) for single phase load control using Arduino nano. Proteus file and the code for simulation are available at the bottom. For video watch at down below or use this link https://youtu.be/VpHoE_2MlEo Circuit Explanation It uses an Arduino nano which receives zero cross pulses (ZVS) at pin at Pin 2 and delayed output pulses are developed at pin 3. Control is done at A0 through a variable resistor (POT-RV1). A small step down transformer delivers 12 volt ac which is filtered by a bridge rectifier BR1 and then a blocking diode D1 and then filtered by capacitor C1 that feeds a 3 terminal regulator that gives 5 volt duly filtered again by C2 for powering the entire circuit. Function of D1 is very interesting. It separates…

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Maintain idling car battery in fully charged condition

It is essential to maintain car battery in full charging condition lying idle for long periods. It often so happens that while the car is attempted for a start it fails to do so. Usually battery capacity falls in unused cars for some small gadgets like remote etc still drawing little power besides bit self discharge of the inherent features of lead acid batteries traditionally fixed in cars. Submitted below a very few low cost DIY tickle charger, as commercial ones are quite expensive. Option1&2 as explained below= Rs 400/-(excluding the power bank ). Option 3= Rs 300/- If your car is parked outdoors with some little chance of sunlight ( even shaded)  falling on the car, then the best option is to use any available  solar cell phone  power bank of around 10,000mAH  along with procured a dc to…

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