Circuit-Zone.com - Electronic Projects
Posted on Thursday, May 2, 2013 • Category: Remote Control
If you want control the DVD or TV/AV system that located in your living room via the remote control when you sleeping in your Bedroom. this IR extender will achieve this for you. Basically, it works as a repeater that moves the IR signal to a different location. This is an improved IR remote control extender circuit. It has high noise immunity, is resistant to ambient and reflected light and has an increased range from remote control to the extender circuit of about 7 meters. It should work with any domestic apparatus that use 36-38kHz for the IR carrier frequency.
Posted on Friday, April 26, 2013 • Category: Power Supplies
Modern power supplies are known as "switching regulator power supplies."
In most switching supplies, the 110 volt AC input is first rectified by
two diodes and filtered by a pair of capacitors. This creates two high-
voltage sources; one positive and the other negative.
A pair of transistors is then used to switch these high voltage supplies
across the primary winding of a transformer. This switching action is
very fast. A typical switching speed is around 40,000 cycles per second
or 40KHz. An integrated circuit is commonly used to control the
transistors. This IC not only controls the speed at which the
transistors are switched, but also controls the amount of time that each
transistor is energized. The output voltage of the power supply is
determined by the "on" time of the transistors. If the transistors are
keep on for a longer period of time, the output voltage of the supply
will rise, while shorter times lower the output voltage. This is known
as "pulse-width modulation."
Posted on Sunday, April 21, 2013 • Category: Motor Controllers
This triac based AC motor speed controller circuit is designed for controlling the speed of AC motors like drill machines, fans, vacuums, etc. The speed of the motor can be controlled by changing the setting of P1 potentiometer. The setting of P1 determines the phase of the trigger pulse that fires the triac. The circuit incorporates a self-stabilizing technique that maintains the speed of the motor even when it is loaded.
Posted on Tuesday, April 16, 2013 • Category: FM Transmitters
Long range, very stable, harmonic free, FM transmitter circuit which can be used for FM frequencies between 88 and 108 MHz. With good antenna transmitter can cover 5km range. It has a very stable oscillator because it uses LM7809 voltage regulator which is a 9V stabilized power supply for T1 transistor. Frequency adjustment is achieved by using the 10K linear potentiometer. The output power of this long range RF transmitter is around 1W but can be higher if you use transistors like KT920A, BLX65, BLY81, 2N3553, 2SC1970 or 2SC1971.
Posted on Friday, April 12, 2013 • Category: FM Transmitters
Building two stage 40 Watt FM Transmitter Amplifier. RF input power should be between 0.5 and 1 watt. Amplifier is powered by 28V power supply. The diagram shows a 2N3375 driving a 2N5643 but there are many other transistors that will work. I used these two transistors just because they were cheap at the time. If any of the variable capacitors are at full capacitance you can pad them out with a fixed ceramic capacitor of suitable value. Extra capacitance also might be needed on the base of the transistors (i had to add 3 100pF capacitors on the base of the 2N5643). The transistors are bolted to a piece of right angle aluminum which is fixed to the metal chassis to dissipate heat effectively.
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