Automatic Power Off Circuit

A while back we got the APRS bug here and it wasn't too long before trackers were being ordered and built and set up with that old rig we couldn't use for much else. It didn't take long and I forgot to turn the rig off and the next day when I tried to start the vehicle, the battery was dead. As a matter of fact I did this several times, and before long the battery was a dud and had to be replaced. So this situation could not go on, first step, I replaced the rig with a Kenwood TM-241a  which has a nice memory feature and an lcd display. Then I came up with this circuit, an collection of ideas and a bit of trial and error. It looks at the battery voltage when the vehicle is off and then when the engine is running. Things are explained on the circuit diagram below.

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