For my projects I have always used hacky power supplies: wall plug + 7805, a USB port or an ATX PSU. I am looking at getting into 3.3 V circuits and I am having trouble getting hold of the necessary regulators in Australia. Can anyone recommend a good lab/bench-top power supply or alternatively a cheap way of getting 3.3 V?
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1\$\begingroup\$ so, where are you located? \$\endgroup\$– markragesDec 23, 2009 at 5:01
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8 Answers
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Decent bench power supplies are quite expensive. However, you've said that you have used an ATX power supply in the past. This is what I've done - I've modified an ATX supply to have a switch, an LED and some 4mm sockets on it with +12V, -12V, +5V, -5V and 3.3V. It's a cheap and very effective way of having a range of voltages available for development.
The ATX supply pin-out is here.
Alternatively, there are a wide range of 3.3V regulators available, including switching ones like the LM2574 or linear ones like the 78L33. Farnell or RS will ship to most places (and they stock both of these parts); alternatively some bits are on ebay (search for 78L33 and you get a few links from "international sellers") and you can probably get them shipped pretty much anywhere. Where are you located?
Apologies for the lack of links for Farnell, RS or ebay: it'll only let me add one hyperlink as I'm a new chiphacker.com user!
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2\$\begingroup\$ This is what I've done and it works quite well. You need to be careful with your ATX power supply choice, however, as not all of them have the voltages you reference. Mine's missing −5V, which is an optional (now obsolete?) part of the spec. \$\endgroup\$– blalorDec 23, 2009 at 10:57
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\$\begingroup\$ I didn't know that ATX had 3.3v in it. Thanks! \$\endgroup\$– jeremyDec 23, 2009 at 13:38
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You could use an LM317 and set that to 3.3V.
The standard part for 3.3V would be the 1117 at 3.3V I suppose. It is indeed somewhat hard to get, even here in Germany (for example, Reichelt only has the SOT 223 variant of the LT1117).
As a lab supply I have a cheap chinese 15V 3A unit. That should also be ok, though I prefer the regulator approach.
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For quick prototyping designs with dual rails supply voltage (i.e. 3.3V and 5.0V), I have recently been using a breadboard with an adjustable breadboard power supply. With this, I can use it with a USB plug or with an ac-dc power adapter and a JST-DC adapter, or for more portability, I use a 9V battery with the JST connector. Search "JST" at seeedstudio for the adapters.
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LittleBirdElectronics in australia sells a simple, build it yourself kit capable of taking in DC from a standard 2.1mm center pin positive barrel and outputting selectable 5v or 3.3v. I myself have one and find it extremely reliable.
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I recently picked up a kenwood bench psu for a very low price on ebay as new old stock, it's only 1A 60V but that's quite enough for 99% of things I will ever do and it cost about 10% of it's list price. So ebay might be worth a look.
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I use one of these:
It's very good. The only shortcoming is the sockets, I'd have preferred terminals with sockets.
answered Dec 23, 2009 at 22:53
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Electronics Express has some power supplies. http://elexp.com/tst-pwr.htm
They also sell some kits such as this one. http://www.elexp.com/tst_3010.htm
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The surplus company Marlin P. Jones (http://www.mpja.com) sells a variety of supplies made by MasTech. I don't know the quality of this brand but if they meet the specs and are reliable they would be a good value.
The Extech power supplies look good. Same caveats.
