Make a Joule Thief. Design Note 20


Joul-Thief-CircuitJoule thief circuit is a self oscillating voltage booster circuit that gives high volt from low volt, say 3 volt from 1.5 volt. So by exploiting this property, we can light a 3 volt LED using 1.5 volt pen cell or charge a mobile phone from 3 volt solar cell or two 3 volt pen cells. It is called as “Joule thief” because it is stealing energy or joules from the battery. Let us design the Joule thief circuit.

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Infrared Alarm System. Design Note. 19


IR-LED-PairThis design note explains how to design an invisible alarm system easily. Infrared Transmitter ( Tx) and Receiver ( Rx) LED pair is easily available which can be used for making this alarm system. Infrared transmitter LED emits infrared rays in the wavelength around 950 nm. This LED is a high current device that can handle more than 100 mA current. The IR receiver LED is a kind of Photodiode that generates a Photo current when it receives IR rays. So the IR LED pair is ideal to make an alarm system that operates both day and night.
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