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Entry  Sun Jan 14 16:52:53 2018, Craig, DailyProgress, TempCtrl, High Current Draw for Vaccan Temp Control Causing Nonlinear Voltage Spikes 20180114_CTNLab_TempControlSpikes_6hours.png
    Reply  Sun Jan 14 20:40:26 2018, awade, DailyProgress, TempCtrl, High Current Draw for Vaccan Temp Control Causing Nonlinear Voltage Spikes 
       Reply  Mon Jan 15 21:35:14 2018, Craig, DailyProgress, TempCtrl, High Current Draw for Vaccan Temp Control Causing Nonlinear Voltage Spikes 
          Reply  Tue Jan 16 10:57:50 2018, Craig, DailyProgress, TempCtrl, High Current Draw for Vaccan Temp Control Causing Nonlinear Voltage Spikes 20180116_OvernightVaccanReheat.png
             Reply  Tue Jan 16 19:10:29 2018, awade, Craig, DailyProgress, TempCtrl, Debugging vac can heater circuit: heat, oscillations, leaking current. 20180115_HeaterCircuit.pdf2018-01-16_19.08.57.jpg
                Reply  Wed Jan 17 23:40:15 2018, awade, Craig, DailyProgress, TempCtrl, Debugging vac can heater circuit issues: oscillations everywhere 2018-01-17_21.20.58.jpg
                   Reply  Mon Jan 22 20:30:11 2018, Craig, awade, DailyProgress, TempCtrl, Debugging vac can heater circuit issues: oscillations everywhere CTN-Lab-Heater-Circuit.pdf
                      Reply  Tue Aug 20 11:19:35 2019, anchal, DailyProgress, TempCtrl, Vac Can Heater Circuit repaired CircuitCloseup.jpgBoxOverview.jpg
                         Reply  Wed Aug 21 16:17:47 2019, anchal, DailyProgress, TempCtrl, Leave the Heater Circuit Alone! 
          Reply  Tue Feb 27 14:17:13 2018, Aaron, DailyProgress, TempCtrl, High Current Draw for Vaccan Temp Control Causing Nonlinear Voltage Spikes 
             Reply  Wed Feb 28 10:20:40 2018, awade, DailyProgress, TempCtrl, Heater and temperaure sensors in cryo lab GroundingDoGroundingDont.jpg
Message ID: 2395     Entry time: Tue Aug 20 11:19:35 2019     In reply to: 2055     Reply to this: 2398
Author: anchal 
Type: DailyProgress 
Category: TempCtrl 
Subject: Vac Can Heater Circuit repaired 

See CTN:2394 for the symptoms and investigation. Open this post at CTN:2395 to see the chain of previous work on this circuit.


Fixes:

  • I replaced the OPA140. This didn't solve the issue.
  • I also replaced the IRF630 MOSFET. For the heat sink, I just used the mica pad and no extra thermal glue.
  • I retouched the solder joints at some places.

Present State:

  • As usual, the sense resistor (1 Ohm) is getting very hot. The MOSFET is not unusually hot after about 10 min of supplying 1.5 A of current.
  • This circuit should be ideally printed on PCB with thick traces and a proper design for heat dissipation. We need to get out of this workaround protoboard circuit! Can be a starter project for a new student or an undergrad.
  • The signal input and heater output all are unnecessarily complicated different kinds of connectors. Particularly from DAC to the box, it could be a much simpler twisted pair of wires.
  • I noticed now that the Sorenson power supply was supposed to be exclusively used for these can heate drivers. It is presently being used for driving EOMs also. I'll switch the EOM drivers to the other Kepco supplies.
  • I checked for oscillations in the heater circuit as mentioned before. Seems like the steps taken before are still working file and I couldn't see any oscillations across the sense resistor.
Attachment 1: CircuitCloseup.jpg  1.808 MB  Uploaded Tue Aug 20 12:42:36 2019  | Hide | Hide all
CircuitCloseup.jpg
Attachment 2: BoxOverview.jpg  1.892 MB  Uploaded Tue Aug 20 12:42:47 2019  | Hide | Hide all
BoxOverview.jpg
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