Best PSU for arduino projects that control AC - Page 1
Forum section: electronics / projects

author: djacobow
author_rank: Super Contributor
timestamp: January 09, 2014, 07:55:10 pm
content: tl;dr: I want a cheap AC-to-5v-DC-1A switcher I can put in a project box and can't find one!Longer:I am "into" projects where an AVR drives some optos or relays or whatever to ultimately switch AC loads.Each time I do one of these it all goes into a box that has an AC plug and one or more AC sockets and .... a little DC input jack where a cheapie DC adapter provides power for the uC.It just looks crazy dorky to have two power inputs.Of course, I could just put the DC adapter in the box, too, but that feels dorky, too, and I end up having to crack open the PSU so I can wire it in and make it fit in a reasonably small box. In this case, it looks OK from the outside, but I have deep shame about the hack job inside, not to mention the fact that I cracked open a PSU that was not ever intended to be cracked open, increasing risk of shock and fire from what was already very likely a dangerous POS to start with.So, what I'd like to do is find a metal caged PSU with AC and DC terminals, that has similar power ratings as a USB charger: 5V, 1A, maybe 2.But I can't find anything like this at Digikey, Mouser, and the like, at least for anywhere near reasonable prices. If the wall-wart version of this costs $5, why should the metal cage or even naked board version cost 3x-10x?What am I not "getting?"

author: don.r
author_rank: Frequent Contributor
timestamp: January 09, 2014, 08:14:07 pm
content: Most cheap wall-warts are small bombs waiting to go off. No clearances, crappy parts, paper thin isolation, sometimes no feedback. They usually end up not capable of even supplying 25% of the rated output... sometimes much less than that.

author: Zbig
author_rank: Frequent Contributor
timestamp: January 09, 2014, 09:49:29 pm
content: Try using "power supply module" or "open frame supply" search terms.

author: Len
author_rank: Frequent Contributor
timestamp: January 09, 2014, 10:07:24 pm
content: It does seem strange that wall-warts are a lot cheaper than board-mount modulesfrom the same manufacturer.Digi-Key search 1Digi-Key search 2

author: djacobow
author_rank: Super Contributor
timestamp: January 10, 2014, 06:02:44 pm
content: I found some at Jameco for about $10/ea (5V, 3A). We'll see how they go. They had two varieties at that price, one encased in plastic (maybe potted inside?) and another in a cage. Both are about 1" x 2" x 1.5"I still feel like this price differential (relative to wall wart which also must have prongs, connector, and wire) is hard to explain.

author: parbro
author_rank: Contributor
timestamp: January 10, 2014, 07:18:08 pm
content: Have you thought about tapping off the AC line to power the micro circuit? Kind of like how an electric meter does it.

author: con-f-use
author_rank: Unknown
timestamp: January 10, 2014, 07:26:15 pm
content: I did a few switch boxes with a solid state relay (less switching current) and a capacitive power supply for the micro controller. Very cheap but dangerous and wastefull if done incorrectly.

author: sleemanj
author_rank: Super Contributor
timestamp: January 10, 2014, 09:50:57 pm
content: Not 5v, but old Brother printers (DCP series and others) have integrated power supplies in a removable metal cased module (once you pull apart the rest of the printer). The module frame is long (depth of the printer front to back) but the board is from memory about 10cm by maybe 5cm, the module could easily be chopped to fit the board more closely - although I pull the PSU board out of the can and mount it directly using it's 4 mounting holes into whatever enclosure I'm using it for.The brother printers I tear down are 30 something vdc output from memory split on 4 wires (2 power, 2 gnd), the printers are free or a couple bucks at most. So for basically nothing you get panel mount IEC socket, not-junk-going-to-burn-down-your-house power supply design, fair amount of current (haven't load tested any though), and fairly compact... and all the other goodies found inside a printer to put in your shed because it might come in handy one day.I just use cheap buck converters to drop the voltage to whatever is required.