# What converter to use?

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.

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).

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.

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?)

• "1. Using a buck converter like this." - That's extremely unlikely to be a buck converter. Most probably, all four of those supplies are the same topology: flyback. The fact that the seller website labels it a buck converter should be warning enough not to buy it. I personally wouldn't trust any components from cheap, unregulated direct-import sources (DX, AliExpress, Ebay, etc) with mains power. The level of cost-cutting and disregard for safety is astonishing at times. – marcelm Jan 8 '18 at 0:09
• To be honest, I never used buck, flyback or switching converters so far. I have quite some 'household adapters' from AliExpress, and so far no problems. But since this is something I make myself, I don't want to use something that's not useful to start with. But I should start reading about what the differences of these converters are. – Michel Keijzers Jan 8 '18 at 0:17
• "I have quite some 'household adapters' from AliExpress, and so far no problems." - And yet, many are dangerous. Read this and view this to get an idea why. – marcelm Jan 8 '18 at 12:43
• @marcelm I read the story and is very informative. I will check what I should do (cost versus safety). In my case the item I want to connect is like 10 euro. To add 20 euro for 'safety' might now be worthwhile, but I see the importance for a $500+ Apple device. – Michel Keijzers Jan 8 '18 at 13:01 ## 1 Answer 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. • Thanks for all answers ... about 1: I don't think using 220V on a perf board is a good idea. I don't have datasheets. And what is a 'real application'.. it will be used mostly to drive a relay to light a 12W LED Par light. And since from another question I know that using 220V for a switch (where a musician from my band will step on) is not a good idea, I need an alternative power source (which is 5V). – Michel Keijzers Jan 8 '18 at 0:02 • I found one similar in the Netherlands, cost about 25 euro including sending (but much, because that would be like 30% of the cost of the entire 'hobby' project). Maybe I should go for the simple adapter and just 'solder' the wires to the two ends of the wall outlet plug. – Michel Keijzers Jan 8 '18 at 0:12 • The one I linked is less than$10 US, which I don't think unreasonable. I've seen folks strap the adapter down and use insulated female spade connectors on the pins, but that's US-style plugs not the round-pin ones you folks use. – Spehro Pefhany Jan 8 '18 at 0:20
• indeed thats acceptable, but in Europe everything is (much) more expensive, and also in most cases transport costs are really high. Importing from the US is in almost any case a no go. That's why probably Ebay/AliExpress is so popular, it can be like factors difference. – Michel Keijzers Jan 8 '18 at 9:44