I've got two home-build Halloween props that currently run from multiple battery packs. I want to switch this to a single wall wart. Here's what I need to power: 1 arduino, 2 Cowlacious audio boards, and 1 Cowlacious Scary Terry servo board in the one prop, and one servo board in the other. 9 volts is a fine input voltage for the power input on each, and ideally I've love to use the barrel connectors on each, since it gives a nice firm connection even when I jostle the setup.

What do I need to look for in a wall wart?

Can I just rig up wires with barrel connectors on one end in parallel off the wall wart?


1 Answer 1


You can use one supply and parallel all the connections providing:

  1. All input voltages are the same.
  2. The supply can deliver more than the sum of all items current requirement.

Since you say 9V is suitable for all items, then 1 is covered. For 2, check the maximum current rating for each and add them together. Then pick a supply that has a current rating which is equal or greater than this value (having some leeway is always a good thing, so multiplying by say, 1.2 is a good idea. Although it's unlikely all items will be drawing max current simultaneously, it's better safe than sorry - many cheap wall warts won't actually manage the maximum rating printed on them safely)

For example, if you have 5 items, all 9V, and current ratings of 50mA, 100mA, 150mA, 200mA and 300mA, then pick a 9V supply capable of at least 800mA. Multiplying by e.g. 1.2 gives you 0.8A * 1.2 = 0.96A, so call it 1A (or more)

  • \$\begingroup\$ Thanks! Turns out the servo boards can draw up to 600mA when actually driving the servo, and I can power any of the boards with between 7 and 12 volts, so I'll likely go with a 12V 2A capacity wall wart. Need to check power consumption on the other boards, but I suspect they are very small. The audio boards only provide line level output. \$\endgroup\$
    – ViennaMike
    Nov 3, 2012 at 16:05

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