Friday, April 24, 2015

PSU update

I completed a PSU board the other day. Nothing much to say about it, I haven't tried it out. It has six outputs per voltage and three voltages - 5V, -15V and +15V. The 5V and +/-15V have separate grounds that can be used as digital and analog ground.

The caps may be a bit close to the heat sinks though, not sure if it is a problem yet.

5 comments:

  1. Hi. Great work. Looks mighty good.
    Regarding caps close to heatsinks.. There is a rule that says "life of a capacitor doubles for every 10 degree Celsius decrease in temperature (within limits)." http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx
    What power will the v.regs dissipate ?
    Since this is not a 24/7 system the caps will be fine.. Unless the sinks get mad hot.
    Hans Petter

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    1. Great, it'll do the job then. I have 11 more of these PCBs and will use at least one of them for something that requires a bit more oomph, I'll just have to keep watch of the temperature I guess.

      I intend to let the circuit draw current from two separate transformers, one for the 5V and one dual secondary for the +/-15V - is this strictly necessary? Could I get away with drawing both positive voltages from the same secondary as long as the total power doesn't max out the transformer?

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    2. If you want better energy efficiency then two transformers will help, I assume there is no large current draw from the 5V ? Maybe currents supplied to digital circuitry ? P_regulator=(rectifiedvoltage-regulatedvoltage)*current ...
      The 15V is for opamp and analog mux right ? .. I'm too inexperienced with noise to go into details here. OpAmps have good PSRR (80dB) (rejection ratio).. If the sampling resolution is 14bit, and one bit is be well below 1 uV.. then I wonder what countermesurements one must take to keep the noise from the MCU low enough.

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  3. Sorry I meant well below one millivolt. Another reason for having separate transformer (or separate winding in the same transformer) is electrical isolation. Is there any reason you would need e. isolation ?

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