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Isolating main power traces on backside of the PCB
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1
Mar 20.2019, 09:37:52
I am currently making a build-in PSU for my own audio-effect-rack-thing.
The internal PSU consists of two print-transformers(THT), one for 6VAC and the second one for 9VAC. These are also pretty low power ones (max 1A on the output).
I want to put the PSU circuit on a perfboard, since this is a simple design. I am already familiar, that there needs to be a decent airgap between main-rails on the PCB. Therefore, I can remove all the unconnected dots, so there can't be a spark.
Now my concern is, when I put the psu circuit in the case, that the backside of the PCB (and therefore the mains(230V) power traces) are touching the case internally.
How can I safely prevent this from happening and is there a better way around ?
My thoughts:
The internal PSU consists of two print-transformers(THT), one for 6VAC and the second one for 9VAC. These are also pretty low power ones (max 1A on the output).
I want to put the PSU circuit on a perfboard, since this is a simple design. I am already familiar, that there needs to be a decent airgap between main-rails on the PCB. Therefore, I can remove all the unconnected dots, so there can't be a spark.
Now my concern is, when I put the psu circuit in the case, that the backside of the PCB (and therefore the mains(230V) power traces) are touching the case internally.
How can I safely prevent this from happening and is there a better way around ?
My thoughts:
- painting the backside with something
- putting a plastic sheet beneath it
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R****ert
Mar 20.2019, 09:42:07
It is also of prime importance to screw the PCB to the case using an appropriate number of mounting holes, and spacers. If the PCB is rigidly connected to the case you can probably skip the plastic, and even the paint, but safety is reduced of course.
For a small, homebrew project a perfo board well fixed to the case is more than enough. If you need to bring this thing around, on stages, where people can possibly touch/spill something on it, please use a real PCB, or paint it with the appropriate material.
Your enclosure is not big enough.
However, most power supplies in metal enclosure have the enclosure grounded, provide enough distance to the board, and add a insulating material sheet as additional precaution.
Beware that sharp pins or soldering residue may not cut into this sheet, care must be taken when choosing the type of sheet. Looking at strenght, insulation and temperature properties. Eg: Nomex or polyimide.
For a small, homebrew project a perfo board well fixed to the case is more than enough. If you need to bring this thing around, on stages, where people can possibly touch/spill something on it, please use a real PCB, or paint it with the appropriate material.
Your enclosure is not big enough.
However, most power supplies in metal enclosure have the enclosure grounded, provide enough distance to the board, and add a insulating material sheet as additional precaution.
Beware that sharp pins or soldering residue may not cut into this sheet, care must be taken when choosing the type of sheet. Looking at strenght, insulation and temperature properties. Eg: Nomex or polyimide.
