Shutdown timer for Tripmate:

I was using my Tripmate with a KPC3+ set for BLT xx:xx:xx CLEAR, and
had the power to the Tripmate ignition switched to time out the APRS posits
when stopped.  I kept finding my car at a "default" location in the center of
town, indicating that the GPS was not locking up during short trips and was
sending the TNC bogus data!  I came up with this 555 timer circuit to delay
shutdown of the Tripmate for 20 minutes, which is long enough for it to acquire
satellites when stopped, and keep it alive during a run into the 7-11 for a candy bar!

The formula for R and C is  T(sec) = 1.1 RC, where R is in ohms and C is in microfarads.
A few common capacitor values for R= 1 megohm:  1000uF for 20 minutes, 470uF for
almost 10 minutes, and 220uF for about 4 minutes.  First transistor is a 2N2222 type,
second one is a TO-220 NPN power transistor (should be available at Rat Shack!)

We can make this more interesting...

...and eliminate the regulator modification inside the Tripmate by doing this to the
output transistor on the timer...

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