The caps may be a bit close to the heat sinks though, not sure if it is a problem yet.
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.
The caps may be a bit close to the heat sinks though, not sure if it is a problem yet.
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Hi. Great work. Looks mighty good.
ReplyDeleteRegarding 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
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.
DeleteI 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?
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 ...
DeleteThe 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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ReplyDeleteSorry 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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