Minimal voltage drop over a 2m distance - Page 1
Forum section: electronics / beginners

author: robdejonge
author_rank: Regular Contributor
timestamp: October 20, 2021, 12:39:40 pm
content: Recently I boughta new power supply. For its depth, I have it up on a shelf so I keep my workspace clear.To get the power down to the workspace, I’d like to install a permanent wire from the output to a pair of binding posts. This wire would be maybe 2m/6ft in length.My question: how do I ensure there is minimal voltage drop over this distance, that the binding posts output as close to the PSU output as possible?My PSU outputs 5A max, so we’re not talking crazy thick wires here. But generally speaking best I could do is use much thicker cable, maybe 2 in parallel for each? Is that right?

author: RoGeorge
author_rank: Super Contributor
timestamp: October 20, 2021, 12:49:29 pm
content: Yes, you can put 2 or more thinner wires in parallel instead of just one thicker wire.There are also power supply that have 4 wires by design, 2 to power the load, and another 2 to sense the voltage on the other end of the powering wires, where the load is connected. Such models of power supply with "sense" inputs are designed to automatically compensate for any voltage drop happening on the two powering wires.

author: David Hess
author_rank: Super Contributor
timestamp: October 20, 2021, 09:29:10 pm
content: Either use thicker wires, or if available, bring the remote sense signals down from the power supply to the terminal block.

author: Capernicus
author_rank: Frequent Contributor
timestamp: October 21, 2021, 01:56:40 am
content: Charge a cap in series with the resistor, and youll see what the voltage is.

author: Vovk_Z
author_rank: Super Contributor
timestamp: October 21, 2021, 08:02:20 pm
content: Here we go again.

author: Dubbie
author_rank: Unknown
timestamp: October 21, 2021, 08:38:01 pm
content: if you really want to minimise the voltage drop, just build your desk out of a solid copper block. (with a split in it for + and -)Jokes aside, some power supplies offer feedback. You could run the feedback wires to your binding posts for practically zero drop.

author: TimFox
author_rank: Super Contributor
timestamp: October 21, 2021, 08:48:58 pm
content: This is why posters should avoid double-posting the same question: two separate chains of answers.If necessary, the first post can be modified later, or a second post added to the thread.

author: tooki
author_rank: Super Contributor
timestamp: October 22, 2021, 02:03:30 am
content: Quote from: TimFox on October 21, 2021, 08:48:58 pmThey were posted seconds apart, so almost certainly unintended, possibly not even realized.

author: Capernicus
author_rank: Frequent Contributor
timestamp: October 22, 2021, 06:07:12 am
content: I know I'm wrong about this one now, thanks. Lets inspire each other!! =)

author: CatalinaWOW
author_rank: Super Contributor
timestamp: October 22, 2021, 05:21:33 pm
content: This is the kind of question that cannot be answered with knowing your needs. But we can provide information to help you decide.First, I would second the suggestion of several above to find if your power supply has remote sense capability. If it does take time to understand what that is. Simply, it measures the voltage at your output point and adjusts the supply output to compensate for any voltage drop in the lines.Second, you can either do your own Google search or look at the attached table to find the resistance of the wires you propose using, and then use Ohm's law to find how much voltage loss you will see under your proposed operating conditions. Looking at the table, with your five amp maximum current, 2 meters of 18 gauge wire (approximately 1 mm diameter) would provide about 0.2 volts drop, which would be fine in many applications, but cause problems in others. Going to 12 gauge wire (approximately 2 mm diameter) cuts this by a factor of roughly 4 to 0.05 volts.Only you can decide how small a drop is small enough, but 0.05 is small enough for almost all applications.Finally, you should spend a moment worrying about the ampacity of the wires. That is: How much current can they safely carry. The wire sizes mentioned above are fine, and if you have reason to use smaller and can accept the voltage drops (or use remote sensing) you should do some googling on the proposed size to make sure you won't start any fires.

author: james_s
author_rank: Super Contributor
timestamp: October 22, 2021, 07:50:44 pm
content: Quote from: tooki on October 22, 2021, 02:03:30 amI did that the other day, I was posting a quick question and then the cat stepped on some keys and I thought it backed out without posting so I posted it again. Then I realized they both posted but couldn't delete the extra one.