Posted on Friday, July 22, 2011 • Category: FM Radio / Receivers
This simple fm radio receiver circuit consists of a regenerative rf stage, TR1, followed by a two of three-stage audio amplifier, TR2 to TR4. In some areas 3 stages of audio amplification may not be necessary, in which case TR3 and its associated components can be omitted and the free end of capacitor C5 connected to the collector of TR2.
Posted on Tuesday, July 19, 2011 • Category: Antennas
This is a low cost fm antenna booster that can be used to listen to programs from distant FM radio stations clearly. The antenna fm booster circuit comprises a common-emitter tuned RF preamplifier wired around VHF/UHF transistor 2SC2570 (C2570).
Assemble the circuit on a good-quality PCB (preferably, glass-epoxy). Adjust input/output trimmers (VC1/VC2) for maximum gain.
Posted on Monday, July 18, 2011 • Category: LED
Here's a simple circuit that flashes an LED on and off. This circuit uses the 555 timer in an Astable operating mode which generates a continuous output via Pin 3 in the form of a square wave. This turns the LED (D1) on and off. The speed at which the LED (D1) is turned on and off is set by the values of R1 and R2.
Posted on Monday, July 18, 2011 • Category: FM Transmitters
This 2 Watt FM transmitter will provide 10km range in good weather conditions. Use dipole antenna for maximum range. Transmitter can be tuned between 88-108 MHz with c5. BB204 could be replaced with conventional led (big) with reverse bias (no light given in correct polarity). 9v power for 2km transmission with good sound quality and up to 18v for 10km range. 2N3553 RF transistors may be replaced with 2N4427 or 2N3866.
Posted on Monday, July 18, 2011 • Category: AVR
I wanted to share my project of modifying the temperature sensor project and turning it into a thermostat with ATmega168. I added a digital output to drive an LED to "warm" the temperature sensor when the current (actual) temperature falls below the desired temperature.
Two push buttons come in as digital inputs one to ramp the desired temperature up and the other to ramp it down.
The logic is simple bang-bang control to turn the LED on and off based on the relationship of actual temperature to desired temperature. It simulates a thermostat in heater mode. The LED is off when the current temperature is above the desired temperature and turns on once the current temperature falls below.
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