Hello Greg.

08 Sep 04 08:29, you wrote to me:

 GM>  -=> Jasen Betts said to Greg Mayman
 GM>  -=> about "" on 09-02-04  15:34.....

 JB>> heck if youv'e got the hardware to do it go with the "lightest"
 JB>> microcontroller you can find and power the sensor (and associated
 JB>> divider chains, adjustment pot, comparator) off one of the
 JB>> outputs or mosfet driven by one of the outputs

 GM> The 16F84 microcontroller pulls only about 6 uA in the SLEEP
 GM> condition. And it can be set to wake itself up when an internal
 GM> timer overflows.

That'd be good.

JB>> if it's a one off: I don't know what you'd pay for a new freezer
JB>> thermostat, but a used one can probably be had cheap if you can
JB>> trust it. noise makers can be had for free from expired smoke
JB>> alarms.

 GM> My experience with thermostats is that the contacts go high
 GM> resistance if they aren't cycled regularly.
 GM> And contacts designed for mains switching usually fail quicker if
 GM> they don't have heavy current and voltage to blast the dirt off
 GM> them.

yeah... maybe an old thermostat could be converted to operate a reed switch
instead of mains contacts. the sealed contacts in the reed switch should
last forever.

Jasen

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