RE: Improvements to cooling system make it worse

[Tom Droege <tdroege@veriomail.com>]

Note that we both should be regulating.  You can tell if the system is 
regulating by running TemPlt and seeing that the temperature settles down 
to some value after overshooting on the way to the final value.  If the 
current is less than the maximum value then it should hold the regulated 
value even if the water temperature changes.

It is not a fast control system (hard to do with large thermal masses) but 
will hold the temperature constant if the water temperature does not change 
too fast.  This is a reason for having a lot of water in the system.  But a 
few gallons should be enough.

With the same command, our two systems should have come to the same final 
temperature.  But there are some imprecise components in the loop, so the 
match is not too bad.  Also, as noted, I did not wait for the system to 
fully settle.  The emphasis in the design was to hold a constant 
temperature rather than an accurate set point.

Tom

At 10:04 PM 1/8/02 -0500, you wrote:
>I was trying to test my mount pointing tonight but just when the Pleides
>came into view so did the clouds.  It's going to be cloudy for a while so
>I'll provide some comparison numbers for TEC current, temps, etc.
>
>Value       TOM       Mike
>TEC Power   11.954    11.35
>+15         14.798    14.66
>+5           4.88      4.86
>Ground      -0.02      0.00
>-5          -5.048    -5.10
>-15        -15.338   -15.01
>VCO Ref.     5.020     5.03
>ADC Ref      2.514     2.49
>DAC 14 set  -2        -2
>DAC 15 set  -2        -2
>DAC 14 read -1.992    -1.98
>DAC 15 read -2.036    -2.03
>
>Temp CCD0  -19.58    -23.64
>Curr CCD0    0.875     0.78
>Temp CCD1  -19.37    -23.06
>Curr CCD1    0.813     0.91
>Water Temp   7.27      4.80
>
>Tom's system and mine show almost identical values.  With nearly the same
>currents we get nearly the same cooling below ambient, in this case about
>28C below the water temp.
>
>
>Mike G.