Hello got a question on powering arduino over long Distance.

Hello i have a question I'm trying to power a arduino over 30 ft long using Ethernet connection. So i supply 5v 0.88a power adapter and on the other end i get out 3.63v some how losing close to 2 volts out of it not sure why is there a way i can boost it? Or so i need a bigger 5v supply with more current on it?


It is probably that the cable has too much resistance. How are you connecting the supply? Is it using a single pair? This would have a sizeable R. Try using two pairs tied together for each side of the supply.


afaik, ethernet wires are 24 (or even 26 gauge) , which means 0.77 Ohm (or 1.22 Ohm if 26) for a30 ft length.
The voltage loss depends on the current your project draws from the PSU. There are only 2 ways to reduce it :

  • reduce the distance
  • use thicker wires

Hello thanks for the reply i can not reduce the Distance because it’s in walls the Ethernet wire is all ready there. my project takes close to 480ma i have tested it. i have a few things on it tempterature sensors a few of them hudmity sensors a touch lcd screen and a few other things on it. its only using single pair for the power I’m using 2 pairs one for power the other pair is to turn off some led lighting. but not part of the arduino project. i have 2 pairs that are free. out of them 2 pairs only one pair is to power up the arduino.

Is it only an Arduino you are powering, you don't give all the details?
What sort of Arduino?
Any shields like an H-bridge or lots of LED's?

I'm guessing 30 feet is close to 10 metres in my terms, which is not that far.
Check your connections and make sure your 5 volt supply is a good unit that is well regulated and has enough capacity.

Sending 5 volts at a few hundreds milli amps over 10 meters should not be such a problem.


EDIT: you replied sooner than my post :slight_smile:

i did say sorry let me rephrase that its also powerings up 3 temperature sensors 2 hudmity sensors 1 lcd 7" also powering up blue tooth module and a Ethernet module.

With all that, I would suggest having a regulated 5 volt supply on the end where you have your Ardiuno and other bits and feeding the cable with a higher voltage, say 12 volts with a power supply capable of at least 1 amp.

Is that an option for you to do?


How much does the wall wart sag under that load?

This is precisely why Power Over Ethernet was invented. Do some research on it and see what modules are available for you.

PoE uses a minimum of 44V, note. When transmitting power over long cables its the
current that leads to loss, so a smaller current at a higher voltage is always preferred.

For instance in the UK domestic power is 240V and distributed on a scale of a few 100m,
local substations run from 11kV or 33kV, and the large national power grid is mainly
750kV. This is all to reduce power loss from I-squared-R heating and allow reasonably
sized wires. The cost of all the transformers and high-voltage pylons is way smaller than
the copper or aluminium needed for the hugely fat wires needed for low voltage

The way to approach designing power distrubution is to calculate the power losses.
(Sounds obvious when you think about it!)

Say you want to send P watts over a certain cable with round-trip resistance R. Choose
an affordable loss (lets say 5%) and so you know you want to waste no more than 0.05P
watts in the wire. I = sqrt (0.05P/R). V = P/I.

Example 3 ohms and 5 watts - gives I = 0.3A, V = 17.
You'd choose 24V and a DC-DC converter at the receiving end to efficiently
step down to 5V (if that's the load requirement). Note the 0.3A in 3 ohm wire
looses 0.27W, indeed about 1/20th of the load power.

Note the DC-DC converter being a switching device is efficient (like a transformer used
for AC mains) and also regulates, so the output voltage is held constant even though
the load may fluctuate (unlike AC mains which varies with load, such as when an
electric oven turns on and the lights dim slightly).

Hello rockwallaby i was thinking the same thing is just using 12v and put something like the 7805 on the arduino side. The power supply i have of 12 has 10a on it. That might do the Trick i will try it thank you.

Hey mark and Paul thank you also for the information there i learn alot about POE and Loss over Ethernet thank you.

Hello just a update i used 2 pair instead of a single pair and put 12v through the cable and on the other end i did a 7805 to bring it down to 5v. Well that seem to work 5v output and works perfect. Thank you,