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Entry  Fri Feb 4 05:26:18 2011, Zach, Electronics, GYRO, PDH2 PCB layout PDH2.pdf
    Reply  Fri Feb 4 08:08:39 2011, Koji, Electronics, GYRO, PDH2 PCB layout 
       Reply  Fri Feb 4 14:56:38 2011, Zach, Electronics, GYRO, PDH2 PCB layout 
          Reply  Fri Feb 4 20:23:13 2011, Koji, Electronics, GYRO, PDH2 PCB layout 
             Reply  Mon Feb 7 13:37:31 2011, Zach, Electronics, GYRO, PDH2 PCB layout 
Message ID: 1288     Entry time: Fri Feb 4 20:23:13 2011     In reply to: 1285     Reply to this: 1292
Author: Koji 
Type: Electronics 
Category: GYRO 
Subject: PDH2 PCB layout 
  • [About the thin lines] Thin lines are not so immune to heat. They may peel off from the board if someone put too much heat on the soldering. Probably 10mil is ok as you are going to ask a company to make resist-coated PC boards. Also, we always modify the circuit in some unknown reasons. If the lines are thicker, we can patch the stages in a flexible ways. Of course, the
     
  • [Chip directions] You will know if you build 20 of different circuits with the chips arranged randomly. The board made by industries are fine as their components are put on the board by a machine and use paste solder and an oven. Our board is made by ourselves. Also we test the board by ourselves. It is always good to have the chips in a single direction. This helps the debugging a lot.
  • [Connectors on the panel] I could not get whether the connectors are mechanically fixed on the front panel or not. We don't want to put strain by the cables to the board because it may crack the soldering of the connectors SOME YEARS LATER. If you have threads on the connectors and fix them on the panels that is nice, but we will have some trouble to fix the board in the box in this case.
     
  • [Extra pads / Extra pattern] There was some confusion because of my short explanation. What I wanted to say was that if you have one or two opamps extra stages which is not connected anywhere, we can use them as a universal board for some unknown purpose in future. i.e. Someone wants to put some signal goes into the loop ==> insert a summing amplifier somewhere in between the stages. Someone needs whitening stage for DAQ. Etc.
     
  • [Components values] This is the philosophie of the low noise circuit: The input stage should decide the input referred noise level of the circuit. It is VERY sad too see the performance of AD829 is spolied by the misuse of the high resistance with low gain at the first stage. The shot-noise level may be higher than 10nV/rtHz, it is good to know the basic rule that the first stage should decide the input referred noise.
     
  • [TP7-TP10] They must be misplaced. You will not be able to measure any sensible transfer functions. Review the schematic and replace the TPs.
     
  • [+/-15V power supply] Review the data sheet. If you can exploit full +/-10V range of the ADC by +/-12V supply, that is still good.
     
  • [Pull up / Pull down] If you pull down the port, we can't turn on/off by plugging a short plug there. Pull up is the way.
     
  • [Chattering] Between the steps the control voltage acrosses the thresholds. If the comparator is enough fast (I suspect so), the comparator switches multiple times. That may cause the multiple switchings of the relays. The relay may be enough slow to remove the chattering. I have no experience of relays.
     
  • [Vref] It is always nice to have Vref on the board.
     
  • [Final remark] Don't forget to make the extra oards for the purpose of the others as the board will be very useful to everyone!
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