Blown-Fuse Indicator

 This is a blown-fuse indicator for a dc power supply. When the fuse is intact, the transistor is base-biased into saturation. This turns on the green LED to indicate that all is OK. The voltage between point A and ground is approximately 2 V. This voltage is not enough to turn on the red LED. The two series diodes (D1 and D2) prevent the red LED from turning on because they require a drop of 1.4 V to conduct.When the fuse blows, the transistor goes into cutoff, turning off the green LED. Then, the voltage of point A is pulled up toward the supply voltage. Now there is enough voltage to turn on the two series diodes and the red LED to indicate...

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Battery Charger, Volatge and Current Control

This project is not so important for those who ride a car every day. In my case, a car is not used every day. In that case, the voltage of a battery is falling and a car sometimes cannot be put into operation. If the battery itself is left for a long period of time, the electricity of it will be lost by natural electric discharge. Furthermore, in the case of the latest car, various kinds of electric devices are always backed up more often with a battery. Therefore, even when the car is not being used, the electricity of a battery is consumed little-by-little. I was creating and using the battery charger which used the solar battery before....

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INFRA RED TEST RECEIVER by: Dmohankumar

This circuit can operate a load such as LED, Buzzer or Relay for a period of  3 minutes through a Remote hand set. It uses the IR sensor module TSOP 1738 which operates in 38 KHz Infrared pulses. The circuit is a Short duration Monostable  using 555 timer IC. Its trigger pin 2 is connected to the output of the IR sensor through R2 and LED. Normally the output of  IR sensor is low. But the timer IC will not be triggered because its trigger pin remains high through R3. When the remote hand set is focused on to the IR sensor and any one of the buttons is pressed, out put of IR sensor goes low and triggers the 555 IC. With the given...

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