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New here + reasonably new to electronics - can solder + hack, but anything finer I need help with!

Building a games rig out of an old console case. I'm looking to have the PSU outside of the unit to keep temps low.

The key component is an Odroid XU4 (http://www.hardkernel.com/main/products/prdt_info.php?g_code=G143452239825) It's rated at 5V/4A. I've been advised that the voltage/A needs to be super steady:

"5Volt +/-5% tolerance is required. So the PSU must have well regulated output at 4.75V ~ 5.25V range."

What I'm seeking to do is also power other components in the unit. Thankfully all at the same voltage:

Powered USB2 Hub - 5V 3A Powered USB3 Hub - 5V 1A HDMI Audio splitter - 5V 1A

Thus, I'll need a new PSU (I'm guessing rated at 5V 9A??). My questions are:

1) How do I split the 5V supply 'cleanly' in the unit - that is to make sure the Odroid is protected. I've been advised against something like this, due to 'voltage drops' or something:

enter image description here

2) Considerations around buying the 5V 9A PSU? Need anything in particular?

Been re/searching for a couple of days now and still none the wiser. Thanks + hope someone can help!

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EDIT: Worried my potential solution got lost in the comments below. So put here.

So will this work:

I can amend my design to use: 1x12Vx2.5A USB3 Hub; 1x5Vx1A HDMI splitter and the Odroid @ 5Vx4A.

I see a 120W picoPSU with ratings: 5V @ 6A, 5VSB @ 1.5A, 3.3V @ 6A, 12V @ 7A, -12V @ 0.05A. So this should work, right? One question though, I'd have to put the Odroid on the 6A 5V line, but would need the 5VSB line activated to power on the other devices?

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  • \$\begingroup\$ ====================================== \$\endgroup\$
    – stigzler
    Jan 30, 2016 at 11:44

2 Answers 2

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It sounds like you could use an ordinary PC ATX power supply. The ATX v2.2 has the exact voltage tolerance you specified for the 5V rail.

You could probably split some of the power directly at the PC PSU since they usually have multiple outputs for 5V.

Not sure which cable copper area you should use since this depends on which length you need. Maybe check the existing Odroid cable and make a guess. AWG 18 will probably be enough for a 0.5m cable to the Odroid.

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  • \$\begingroup\$ Thanks Dejvid, but looking to have a switched power supply outside of the unit. Besides this, an ATX PSU (or many others) wouldn't fit into the unit. Thanks anyway. \$\endgroup\$
    – stigzler
    Jan 27, 2016 at 22:22
  • \$\begingroup\$ There are plenty of examples of running a PC PSU externally. Google it! :) \$\endgroup\$
    – Dejvid_no1
    Jan 27, 2016 at 22:28
  • \$\begingroup\$ If you're not really looking to "go deeper" with doing EE/homebrew for a learning experience here, than this would probably be your best option. You could easily "tap into" the +/-5V wires from a few of the HDD connectors from the external PSU to run your usb hubs & HDMI splitter, then tap one of the +/-5V pairs from the ATX connector to keep max stability for your Odroid. \$\endgroup\$
    – Robherc KV5ROB
    Jan 27, 2016 at 23:11
  • \$\begingroup\$ Thanks. Quick look at it - would a pico psu be a good way to go? Would this provide 2 5v rails? \$\endgroup\$
    – stigzler
    Jan 28, 2016 at 8:32
  • \$\begingroup\$ No, I don't think a Pico ITX(?) will be enough. The ones I've seen only has about 6A peak current on the 5V rail. \$\endgroup\$
    – Dejvid_no1
    Jan 28, 2016 at 12:39
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You can "buffer" the stability of the supply to the Odroid by placing a (as large as you can afford) capacitor parallel to its inputs, then place (large) inductors (with protection 5V zener diodes from the positive, post-inductor supply to ground) in series with the two usb hubs. In this way, the inductors will "smooth" spikes in current to the usb hubs whenever a new device is plugged/unplugged, while the capacitor helps stabilize the voltage "seen" by the Odroid. However, you may find that the HDMI audio splitter may not have great sound clarity if you put too large an inductor before it (although having a large capacitor after the inductor could help this). Also, I would recommend finding a power supply capable of supplying at least 12-15A @5v, since your summed amperage draws equal 9A & very few power supplies are truly stable when pushed too close to their max rated output; undervoltage "events" will likely be common if you keep less than a 25% "reserve" on the supply.

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  • \$\begingroup\$ This seems a little excessive, any usb hub would already have power caps on the PCB. When margin-ing specs from a systems perspective do you really need double the current? Is each device going to be pulling 100% power all the time? The answer is probably not, if you measured the power from the USB hubs with nothing plugged in, I would expect 50mA maybe 100mA worst case. Each port can 'legally' only supply 500mA if the devices use it. \$\endgroup\$
    – Voltage Spike ♦
    Jan 27, 2016 at 21:27
  • \$\begingroup\$ Wow. Thanks for the answer, although this looks way beyond my skills. I was hoping there was an 'off the shelf' solution or at least a board I could buy and solder to or something. Didn't realise this would be so complicated! \$\endgroup\$
    – stigzler
    Jan 27, 2016 at 22:27
  • \$\begingroup\$ laptop2d: He asked for a setup to keep within +/-5% of 5.0V from my personal experience, many 5V power supplies can be dragged down to 4.3-4.6V anywhere from 70%-100% loading, with both voltages being too low to fit the spec in the question. As such, I recommended upsizing the power supply by at least 25% (a 12A supply would be +33%). stigzler: what I'm envisioning would only require ~8 components (2 caps, 3 inductors & 3 zener diodes), and should be accomplishable with a small breadboard. If you're interested, I'll figure out how to add a circuit diagram to my answer for you to use. \$\endgroup\$
    – Robherc KV5ROB
    Jan 27, 2016 at 23:01
  • \$\begingroup\$ The 12A switching PSU I can do! The rest... not so sure! Are there any boards you can buy which are setup for what you're advising? Thanks \$\endgroup\$
    – stigzler
    Jan 27, 2016 at 23:07

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