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I want to place my Raspberry Pi in a remote location to act as a surveillance camera and need to run a power-ONLY USB cable over a long distance of 30 to 50 feet.

Can I safely extend a normal USB 2.0 cable by just connecting the VBUS +5V RED and black GND wires to one pair of a CAT-5 cable reusing the TYPE-A and Micro-B connectors from the USB cable?

I would leave the data wires disconnected.

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    What did you end up going with ? Does your pi work properly? Any issues? – Ted Taylor of Life Aug 27 '16 at 21:51
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It should be possible to run power over this distance, but you should use heavier gauge wire. CAT5 uses 24/26 AWG; a 50' loop of 26AWG would have a resistance of 4Ω; drawing 700mA would give a voltage drop of 2.8V - this would almost certainly cause problems.

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    Wow, I didn't consider that the resistance of the cable could lower the voltage so much! I was using my alarm system as an example where there is a transformer in my garage and telephone cable from there to the alarm system 20 feet away. However, based on your guidance and @ppumkin's, that system must be using a voltage regulator in the alarm system to down-convert a higher voltage to the required stable system power voltage. – HeatfanJohn Sep 13 '13 at 15:17
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    Therefore according to this website 30' of 18 AWG wire has a resistance of .192 Ω which at 700mA will give a voltage drop of 0.1344V, would that work? – HeatfanJohn Sep 16 '13 at 22:55
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    You have to double this, because you have a loop, but this should be within the normal 5% tolerance. The Pi actually runs from 3.3V with an internal regulator (the 5V is used for USB), so the actual CPU should be OK. I have powered remote devices using heavy duty speaker cable. If it is a critical application, one of the more robust solutions may be appropriate. Incidentally, using paired cable you should not have interference, unless running parallel to very dirty power. – Milliways Sep 17 '13 at 0:45
  • Ah, yes it's a loop, that's how you got 4Ω for a 50' run. – HeatfanJohn Sep 17 '13 at 2:19
  • I'm going to try using heavier gauge wire. If that causes problems I have a low-cost 5V USB regulator on order and will switch to using that with higher DC voltage. – HeatfanJohn Sep 18 '13 at 17:26
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it may introduce a whole lot of inductive noise and depending on your environment it may work or your board may keep resetting or getting all kinds of glitches. (such a cable acts as a huge antenna and there will be bad spikes in power both ways - and RPi doesn't have big capacitors to compensate for that).

Just run a mains AC extension cord and put a USB charger at the destination to power RPi up.

  • A mains would also act like large antenna :) And what is worse runnin 220 outside needs to be well protected in case a cat/dog bites it making it kentucky fried!! It just needs a capacitor like 500uf 10v or higher adding on there and it will sort any dips. Spikes... that is another story though and is bad on 220 or 5v. The source needs a surge protector or better yet surge protection on the whole house. – Piotr Kula Sep 13 '13 at 15:02
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    A mains of 230V is 46 times more than 5v which makes all inductive spikes relatively 46 times smaller. Every charger contains all kinds of protective circuitry - capacitors, zener diodes, coils to choke all kinds of spikes and gaps, so instead of cooking your own, you can use something made professionally. Trust me, I work with infrastructure that needs low-voltage power of ~40mA over distances of ~100m. Even 24V is just not viable because 40mA of current can be induced by itself from interferences alone over such distance and reads as short circuit, current in unpowered line. – SF. Sep 13 '13 at 15:46
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    cntd. As result we just run 230V there and convert to needed voltage on the spot. True running 230V is not trivial; but 230V is dirty almost "by definition" and any of its sinks is adapted to it; power supplies clean it. OTOH, RPi creators choose USB 5V for the precise reason it's ubiquitous, cheap and clean. RPi is just not made to handle to dirty power. – SF. Sep 13 '13 at 15:53
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    24V would be fine, but requires two adapters. Since both ends of the 230V must be kept dry (RPi must be kept dry after all!) as long as you use a reasonable, grounded cable with no breaks and gaps, and run it either high or low enough so that people don't trip on it, it's fine. – SF. Sep 13 '13 at 17:13
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    In Great Britain - running a 240V outside supply is subject to Part P of the U.K. Building Regulations - so you'd need a qualified Electrician (or someone else with the Part P certification) to put in that cable if there is any hint of permanence about it. Even if not, (you are temporarily using an extension lead just for an hour or two) you MUST ensure that the supply is protected by a 30mA (maximum) RCD device inside the property. – SlySven Dec 2 '15 at 16:49
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If you are planning to have Cat5e running to it then why not just use PoE.

PoE injector/splitter kits are relatively cheap, here is one which would likely work for your situation as supports 5V output.

  • I did mention using a splitter. – Dan Nixon Oct 11 '13 at 18:40
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As milliways has answered you will get a steep voltage drop on such a distance using 5volts.

This is common problem in all long distance power transmission.

The best solution is to use a 24 Volt power supply and use a 5 volt regulator on the Pi side. There are cheap modules available or you can easily make your own regulator using a capacitor and a voltage regulator 78xx. (Sparkufun) (Wikipedia)

But it would be more efficient to use a switching regulator V78-1000 if you want to save power.

enter image description here

The reason using 24 volts is better is:

  1. The obvious voltage drop problem on a long wire.. this wont matter if you regulate down to 5v
  2. Higher volts does not need higher amps (its actually opposite). So you can use a 0.5amp power supply but when regulating you will inface get more amps to use on the 5v side! This will help use a thinner copper wire (like network cable) which will reduce the voltage drop (less resistance)

FYI - Some POE standards uses up to 50 volts to power remote devices.

Just a side note to consider but not critical - As commented by SF. It is better to send AC current- but 220volt might be dangerous so a compromise is sending 24volt AC and rectifying (also easy and cheap using 4 diodes) and regulating it at the Pi. That is because of various inductance problems and stuff I am not really all that familiar with.

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    Quote:"So you can use a 0.5amp power supply but when regulating you will inface get more amps to use on the 5v side!" This is not true, when using a linear regulator like 78xx. You have to have the exact amperes both on the input and the output side, infact even more on the IP side due to Ground leakage. – Vaibhav Garg Sep 21 '13 at 12:28

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