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What will happen if I connect 4 identical Orange Pi One boards (which require 5V @ 2A) in series to a 20V @ 2A power supply? The reason I want to do this instead of using four 5V power supplies or one 5V @ 8A in parallel, is because the 20V one is much cheaper. The boards are identical but my understanding is that they draw different current depending on the load (I don't know how much current they draw).

Stefan D
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    Any junked tower PC will contain a 5V supply at much more than 8A. There are instructions for getting them to behave (turn on or off) online. –  Apr 29 '16 at 10:14
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    Chances are excellent that the boards will all be destroyed. – Spehro Pefhany Sep 15 '16 at 18:01

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The boards are identical but my understanding is that they draw different current depending on the load

Here lies the problem. One rather important consequence of series connections is that all components in a series connection have equal current through them. This scheme would be fine for a set of lightbulbs or other simple resistive loads, but this is not a good idea for complex loads (Orange Pi boards qualify as complex loads).

Edit: also, a quick search reveals that 5V, 10A power supplies can be had for ~20USD, or ~25USD if you want enclosed, which really isn't all that expensive for a project involving four Orange Pi boards. Or heck, you could just buy a bunch of 2A USB supplies, which are dirt cheap. Also, unless you're going to be running all of these boards flat out all the time, you can get away with derating your power supply a little bit. All the boards drawing 2A is an absolute worst case, and probably will never happen, so a 6A power supply is probably fine.

uint128_t
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  • Yes... The 20 volt will not be shared equally by the all loads. Lightest load will see highest voltage and the heavier load will see lower voltage. – soosai steven Apr 29 '16 at 03:58
  • The supply I had found was $3.34, that's why I thought it could be an attractive choice. I think I will just get an old ATX psu and use its 5V output in parallel, will probably buy more Orange Pi boards to lower the cost per unit. – Stefan D Apr 29 '16 at 04:13
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Asside from the load issue, your solution would have each board at different ground potentials. Communication would require galvanic isolation

swordfish45
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