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[aprssig] BOUY 4

Greg D. ko6th_greg at hotmail.com
Thu Aug 7 04:42:19 UTC 2008


But how would you know for sure which way the latch was set?

Why not just have a reed switch remove the bias on a power FET (short gate to ground)?  Or even better, have it drive a CMOS inverter to drive the power FET, wired so that the no-magnet state turns on the power, and the magnet state turns it off?  With a such a high impedance input on the inverter, the magnet state would be drawing a few microamps at most through the voltage divider, and the rest of the logic is essentially inert with no clock running.  You don't need to turn off absolutely everything, you just need to make the off-state current draw low enough to be ignored.

Just make sure the magnet comes off before launch.  Maybe stick it on with water soluble glue?

Greg  KO6TH


----------------------------------------
> Date: Wed, 6 Aug 2008 13:34:11 -0500
> From: kg4wsv at gmail.com
> To: noskosteve at yahoo.com; aprssig at lists.tapr.org
> Subject: Re: [aprssig] BOUY 4
> 
> I'd use something like the magnet +  reed switch (in conjunction with
> a latching circuit, so the need for the magnet is temporary) to turn
> _on_ power, and use an APRS command to a Tracker2 to turn off power.
> 
> -Jason
> kg4wsv
> 
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