[aprssig] Tracker power control relay

Scott Miller scott at opentrac.org
Mon Jul 19 16:20:04 EDT 2004

> I like the feature.  The only thing I don't like about TT's implementation
> is the fact that it is designed to also power a GPS.  Thus if the GPS
> looses it's lock for whatever reason it will leave the relay powered up
> until the GPS relocks and a packet is sent.  Thus it can kill a car

Does anyone use the feature to control power to a GPS?  Seems like it'd only
be useful if you're not transmitting more than once every 10 minutes or
so... and even then, some GPS receivers will take that long to cold start.

> I've been considering picking up an OT for a while but didn't realize that
> you didn't have support for the relay.  This would be a necessity to me in
> my next application as well.

Soon!  Would have done it over the weekend, but was busy with SAR training.
Spent most of the day riding quads and driving the HMMWV - training doesn't
get much more fun than that.

Now, one thing I've got to consider is what to do if it powers up the radio
and can't get a clear channel for some reason.  Maybe it's a weather station
and someone's installed equipment nearby that's got the squelch open
continuously.  It needs to be able to either time out and give up, or maybe
transmit anyway after a certain time period.  Hmm... so that could be three
items in the config:

Power relay delay: [  ] seconds
Max channel clear wait time: [  ] seconds
On timeout, (*) give up ( ) transmit

I'll probably have it hold the last GPS position as soon as it goes into the
relay startup delay, but you could wind up with a stale position if it has
to wait long.  Wish I had enough RAM to hold more than one posit...


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