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I've always wanted a network PDU, however they're super expensive. What would be the downside to building one myself with a,

For comparison a network PDU seems to start around $373. Do switched power supplies have more complex hardware that does something special? Or, is that all there really is to it?

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The commercial unit contains a power supply, software and probably is well designed so that switching inductive loads won't cause the controlling computer to go nuts from time to time. They probably also use relatively good quality relays with genuine cUL listing.

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  • \$\begingroup\$ "Comes with a power supply." You mean to power the arduino (internal relay control mechanisms)? \$\endgroup\$
    – Evan Carroll
    Oct 21, 2015 at 18:18
  • \$\begingroup\$ Also not sure how switching loads would cause the controlling computer to go nuts? Could you explain a bit, I'm new. \$\endgroup\$
    – Evan Carroll
    Oct 21, 2015 at 18:18
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    \$\begingroup\$ Switching inductive loads often result in in voltage spikes or even sparks. It can not just go nuts, but simply burn if not designed correctly. \$\endgroup\$
    – Eugene Sh.
    Oct 21, 2015 at 18:32
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    \$\begingroup\$ @EvanCarroll I think Spehro means COTS item may or may not have a snubber circuit to reduce effects from switching inductive loads, which include but are not necessarily limited to audible noise over your speakers, temporarily blanking of a monitor or otherwise restarting equipment. \$\endgroup\$
    – jippie
    Oct 21, 2015 at 18:39
  • \$\begingroup\$ @jippie very good, something I can wikipedia. That's a start and it puts me in the right direction. Thanks! \$\endgroup\$
    – Evan Carroll
    Oct 21, 2015 at 18:50
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The commercial PDU you link to also supports current metering (for each port it seems), so it's not just a bunch of relays. Also (not included in that price) "Optional ENVIROSENSE temperature/humidity probe enables remote monitoring of in-rack environmental conditions and alarms for up to 3 user supplied contact-closure sensors."

Most of the rest are software features, you can get SNMP on arduino as well and probably whip up your own code to do "User defined power-up and power-down outlet sequences" or "Programmable load-shedding of less critical devices at user-defined intervals". And that PDU has a web interface too (not just SNMP), which you'll need code if you want that.

A non-trivial cost chunk goes into testing all that, warranty, etc. Also a 1U empty rackmout case will cost you [new] a little bit more than an arduino. Add the tooling to put all the stuff into that, etc.

You can look at this vid (and photos, PCB layout, schematic) to see what's inside an entry-level DYI networked PDU (no current metering).

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  • \$\begingroup\$ I was just going to stick this into a 1U used PDU (no network monitoring) which is like $30. And the temperature and humidity sensors are only a few bucks. But, yet metering is out of the question and would probably cost a nice bit to hack up. I don't need it. \$\endgroup\$
    – Evan Carroll
    Oct 22, 2015 at 2:57

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