[LinuxPPS] thermostat

[Remco dB]

OK, here answers to the questions of Hal and Udo

Hal: 
Yes, the diodes are mounted in a subtoptimal way. It was/is an experiment
and I could not find the space to mount the diodes more directly on the 
crystal. My idea was: 'it is copper foil and the conduction is such that 
other influences may be of insignificant proportions'. 
Anyway, the results are promising. But, improvements could be made to 
mount the diodes more directly onto the crystal. Of course you can use 
a smaller (PNP) transistor like a BC160 or BD136 or something. Point is the 
isolation of the collector. My next thermostat will be a version with the 
collector of the transistor to ground and the resistor in series with the 
emitter. However, current regulation will be difficult then.. we'll see. 
The result here is +/- 5-10 us -> +/- 1 us (which I think is a significant
improvement with such a small investment)

About the power consumption. The power consumption depends (of course)
of the flowing current. When the thermostat is in lock it draws approx. 90 
mA at 12V. I feed the thermostat with the +12V from the harddisk connector. 
A normal computer power supply has more than enough power to power this
and...

Udo: 
Also a GPS receiver like an Oncore or Garmin LVC18 can be fed from an USB
port without any problem. 

Don't be afraid of hardware... it doesn't bite! (when you know and dare what 
you're doing  ;-) 

Remco