AUTOMATIC_SHUTOFF_FOR_BATTERY_POWERED_PROJECTS

Published:2009/7/6 5:21:00 Author:May | From:SeekIC

When S1 is depressed, C1 begins to charge to the supply voltage. That places a forward bias on the gate of Q1 turning it on and supplying current to load resistor RL. When the charge on C1 leaks off, the transistor shuts off, cutting off current to the load. That load could be anything from a transistor radio to a child's toy. Transistor Q1, available from Radio Shack as part No. 276-2070, is rated at 0.5 A at 60 Vdc. With a supply voltage of 9 Vdc and with C1 rated at 0.22 μF, a delay of about one minute is produced; with C1 rated at 10 μF, the delay is about an hour.



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