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| Is this power supply regarded safe? |
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| ArthurDent:
--- Quote --- "Look on the pad on bottom left corner." --- End quote --- That pad is also very close to the ground plane on the front side of the board. That is another place that I would modify, as well as the small pads on the back side for the voltage select jumpers that are very close to the trace that goes between them. I assume they rationalized that the pad you mentioned was zero volts so it was o.k.to be that close to the ground plane. I'd eliminate the whole (or is it hole?) problem by not using that section of the PC board at all. You could make a small perf board version of that section with proper spacing and eliminate the entire mess. |
| CuriousAbe:
Thanks for the replies everyone, my hunch about this was correct. I've forwareded the thread to my friend who sent me the photos(who I think is also a member here). |
| Dr. Photon:
You could always buy the kit but just do the mains wiring off-board? |
| Siwastaja:
As some others have pointed out, you have missed the bigger problem completely. Live - neutral clerance is, if not safe and up to regulations, at least... quite OKish, when compared to the massively horrible and immediately lethally dangerous lack of clearance between primary and secondary (through the secondary side main copper pour). (I'm assuming that the low voltage side ends up being touchable by the end user, through connectors or otherwise. If the complete product is fully physically isolated, please ignore this post.) Exact requirements vary per legislation, but primary-secondary creepage and clearance requirements are always bigger than the live-neutral limits, and for a good reason: arcing between L and N only tends to cause increased risk of fire, whereas between the live (FYI: neutral wire is always treated as live as well) and the protected side, the result is not only a risk of fire, but an imminent, invisible electrocution death trap as well. Eyeballing from the image, primary-secondary clearance seems way below 1mm if not 0.5mm - reason for immediate product recall due to being a massive death trap. You tend to see beginner issues like this on Western products designed by amateurs, often accompanied with a marketing assumption of high quality. Chinese power supplies get a lot of attention for doing this sort of thing, but they typically have better idea about what they are doing. |
| bloguetronica:
Well, I cannot regard it as safe, as others said. There is not enough insulation clearance, and I see jumpers that pass 240V flying above the board, unprotected. I don't know what was the idea of the designer, but if I was on his shoes, I would move the jumper/240V section out of the board. Only SELV would go into that board, by my standards. If you need to use high voltage on your board, because you are using one of those encapsulated transformers, you should: 1- Leave enough clearance; 2- Apply a guard ring connected to protective earth, around the tracks you wish to isolate from the secondary, provided that point 1 also applies to the guard ring. See the attached files to see what I mean. However, I should note that this design is far from ideal, just because the mains terminal block doesn't have enough clearance between the pins. Despite that, the mains are adequately isolated from the ground plane. The board layout that I've attached would be 100% correct if a different terminal block was used at that point. Kind regards, Samuel Lourenço |
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