With the amazing amount of devices available to anyone, each one usually comes with it's own power requirements!

Right at this moment, on my work table i have these adapters which I have at arms length for various things (and many more which I shall not list):

  • 9v dc 500ma (Arduino)
  • 12v dc 1a
  • 5v dc 700ma
  • 5v dc 2a

How can I simplify my DC power requirements? Does a device exist where it's a power supply and can output any combination of voltage and current? And also have flexible adapter plugs?

  • \$\begingroup\$ You know that a 5 V, 700 mA source can be replaced by a 5 V, 2 A source, right? \$\endgroup\$ – endolith May 4 '11 at 14:22

Get a bench power supply. I use one of these, it won't cost much more than your selection of mains adapters, and is a lot more convenient. I've made up a variety of leads that plug into it for powering various boards. Having voltage and current displayed is very useful, as I can see immediately if there is a short on a prototype.

  • \$\begingroup\$ I was just thinking the same myself (about "mutually recalibrating" the votes, that is!). \$\endgroup\$ – MikeJ-UK May 4 '11 at 13:27

You can get multi-output adapters with a selection of reversible tips. Typically, these provide switchable 3V, 4.5V, 6V, 9V & 12V (No 5V) with half a dozen or so tips (1.6mm, 2.1mm, 2.5mm etc) which can be reversed for centre-negative/centre-positive applications.

The only problem is that you have to be very careful to check the voltage & polarity settings before plugging them into your expensive gadgets!.

  • 2
    \$\begingroup\$ Anyone care to comment on the downvotes for myself & Leon Heller? Both answers seem perfectly reasonable to me. \$\endgroup\$ – MikeJ-UK May 4 '11 at 9:37
  • \$\begingroup\$ I upvoted your answer, perhaps you can return the favour. \$\endgroup\$ – Leon Heller May 4 '11 at 12:52
  • \$\begingroup\$ All answers were down-voted for some reason... very weird \$\endgroup\$ – W5VO May 4 '11 at 13:20
  • \$\begingroup\$ I downvoted Leon Hellers entry because I think it's a bad idea to use a bench power supply to supply power to a bunch of gadgets to save space+energy, which is what I think the OP was asking for. If he wanted a laboratory power supply, then Leons answer would be the correct one. \$\endgroup\$ – dren.dk May 4 '11 at 14:35

First of all, the current rating on the power supply is a maximum current the psu can deliver, so if you have a 5V / 700mA and a 5V / 2A supply, then a single 5V / 2.7A supply will do the job of both of them.

So, what you need to figure out is what voltages you really need and sum up the current for each of them.

The voltages you need might not even be all the once you have now.

Lots of devices will be able to work fine on a much higher voltage than the supplied PSU, I have several network switches that come with 9V supplies, but they are built for and works perfectly on everything from 6V to 24V.

That Arduino will be happy with 12V, though the regulator might get a little hot if you are loading it down a lot.

The only way to know for sure which voltage a device will work with is to open it up and look at the regulator section of the device.

Your 5V devices will probably not be happy with 12V, perhaps a 12V powered USB hub would be a good idea there.

All my on-always gear is powered by a single 12V / 5A power brick, which is much more efficient and compact than the 8 separate wallwarts that the devices came with originally.

I made a small box with a load of 5.5mm barrel DC connectors, then I bought a good hand full of DC connectors that fit them and then I either cut the original power cables and fitted my new DC connectors or I simply made all new power cables for things.

  • \$\begingroup\$ A 6V 1,000mA adapter might not be a perfect substitute for a device which expects a 6V 100mA adapter. Some adapters put out a higher-than-spec voltage when they are used significantly below their rated current. A device which uses a linear regulator to supply up to 100mA at 5 volts might expect to have the regulator dissipate 100mW (1V @ 100mA) when drawing 100mA, and wouldn't mind if it had to drop 2V when the device was only drawing 50mA or even 4V (9 volt supply) when the device was drawing 25mA; it might not be quite so happy, though, with an adapter... \$\endgroup\$ – supercat May 4 '11 at 15:33
  • \$\begingroup\$ ...that puts out 8 volts@100mA, which is something a nominal 6V 1000mA adapter might do. \$\endgroup\$ – supercat May 4 '11 at 15:35
  • \$\begingroup\$ You are right that unregulated PSUs will put out a higher voltage, if it's not loaded down enough. I should clarify that I was talking about regulated switchmode PSUs, which will put out the specified voltage no matter what current is being pulled. \$\endgroup\$ – dren.dk May 5 '11 at 7:49
  • \$\begingroup\$ True, provided that there's at least a minimum load. Some switch-mode power supplies won't be happy without a certain minimum load; supplies with higher maximum loads will often have higher minimum loads (many supplies may be able to dissipate power internally in the absence of an external minimum load, but this will of course waste energy). \$\endgroup\$ – supercat May 5 '11 at 14:44

Consider an adjustable dual-power supply such as this 3-A one from TI. Its eval board is US$25.


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