What converter to use?

by Michel Keijzers   Last Updated January 08, 2018 00:25 AM

I am going to build a stage box, and I need 5V for that (to add some logic, maybe even later an STM32).

I also need mains (220V) for a 12W RGBW LED PAR light.

At first I thought to put in the box a 'wall socket' with two 220V plugs, but since the 12W needs to be switched by a relay, only for 5V I need a solution.

My thoughts were:

  1. Using a buck converter like this. However, I don't see any holes, so I don't know how to fix it inside an enclosed box. pic

  2. Using an already enclosed converter like this. I also don't see holes here, but at least I can glue it on one side. This one is twice as expensive (but still cheap). pic

  3. Using a switching power converter like this. This one has holes, but cost even more. And I don't need the power it can deliver. pic

  4. Using an adapter (220V->5V). pic

I'm quite a novice, so these questions might be trivial but not for me:

  1. About option 1: How can I 'fix' this part in an enclosure? With using glue? I don't think it will be safe for 220V, especially if I want more in the enclosed box (like the STM32 later).

  2. About option 2 (but also 1/3): Can I safely put this in a 'closed' enclosure? I think I can since the power usage is quite minimal (200 mA, maybe even less). So actually option 2 is already an enclosure, but I want to put it in a bigger enclosure with all logic (STM32 possibly and the relay).

  3. About option 3: I like the holes, but that's it. Feels awkward to buy this just because it is the only solution with holes to fix it.

  4. About option 4: I feel more comfortable with an adapter, however, I really don't like the idea to put inside my stage box a wall outlet, just to put the adapter in. I though about cutting of the 'adapter' part, but still what I keep is essential option 2.

(Actually all questions come down to: how should I fix/consolidate them in an enclosure and will I get problems with heat?)

Answers 1

  1. Pins to another board (like a "perf board") with pads (or a PCB). Same as #2.
  2. "Safe" is relative for those things. None of them bear any approval markings, so you have to assume that each could kill you or burn your house down. If you have no datasheet there's no way to tell how inefficient they are. They're probably just as (un)safe in a moderate size enclosure as a huge one.
  3. That one looks a bit better designed (EMI filter, inrush NTC) but not everything that could kill you is visible.
  4. That one might have non-fake approvals but as you say is not convenient.

If this is a real application, I strongly suggest you use something from a reputable manufacturer with (non-fake) approvals. It will cost more, but you'll be able to sleep at night. Try a small (eg. 10W) enclosed supply from Meanwell (from a reputable franchised distributor not ebay/Ali).

All your questions should be answered by the manufacturer's data sheets and supporting documents (application notes etc.). If they can't supply those documents, you should not buy the product, in general but particularly for a safety-critical component.

Spehro Pefhany
Spehro Pefhany
January 07, 2018 23:55 PM

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