DC barrel jacks, safe amperage? - Page 1
Forum section: electronics / beginners

author: rthorntn
author_rank: Frequent Contributor
timestamp: October 24, 2018, 02:46:00 am
content: Hi,I have an ITX server motherboard that gets 12v through an 8-pin ATX EPS connector, I'm probably doing to have to make a cable up.Peak power draw on the motherboard is about 120W, now the power supply I have is an 150W switchmode brick PSU with a 5.5/2.1mm jack.I'm worried that 12.5a on a 5.5/2.1mm jack is probably a bit much?What would you do, basically I have 8 cables coming out of the EPS connector that need to go onto 2 lugs?If the recommendation is to remove the 5.5/2.1mm jack, what to replace it with, preferably something I can easily disconnect and also the server end should be panel mountable?Thanks.Richard

author: TERRA Operative
author_rank: Super Contributor
timestamp: October 24, 2018, 03:28:26 am
content: The datasheet from the manufacturer should tell you the maximum current it can handle.

author: Brumby
author_rank: Unknown
timestamp: October 24, 2018, 03:36:21 am
content: It's not the most wonderful news if you're not into reading datasheets - but it's something you will do well to learn. Your question is best answered by doing exactly this.It is also significant that you find therightdatasheet for the product. Different manufacturers can make a physically compatible product that has different capabilities - such as maximum current capacity.

author: Ian.M
author_rank: Super Contributor
timestamp: October 24, 2018, 03:38:05 am
content: I would be deeply suspicious of anything that puts more than a couple of amps through a 5.5mm OD power jack. Even if both plug and socket are rated for the current when new, once they've got a bit worn, reducing the contact pressure, and some dirt or tarnish has built up, there's a significant risk of overheating leading to total failure.

author: rthorntn
author_rank: Frequent Contributor
timestamp: October 24, 2018, 03:45:18 am
content: Thanks, I am suspicious, hence the post.The KFD-150W PSU is actually 5.5mm x 2.5mm.My connector is Jaycar and I don't see a datasheet or a rating:https://www.jaycar.com.au/2-1mm-bulkhead-male-dc-power-connector/p/PS0522Any suggestions on what to do?

author: Ian.M
author_rank: Super Contributor
timestamp: October 24, 2018, 03:52:00 am
content: No datasheet = crap. Try a different supplier (e.g. a major distributor with working parametric search on their site), and look for a branded connector with a datasheet.Whether or not you'll get away without changing the connector on the PSU depends on the average current the motherboard will draw in your application, which will be heavily dependent on its computational load and the CPU and RAM installed.

author: rthorntn
author_rank: Frequent Contributor
timestamp: October 24, 2018, 03:59:44 am
content: Thanks but I would like to avoid searching for a 12.5A rated 5.5mm x 2.5mm connector (that probably doesn't exist) when I could just switch it out for something better, come to think of it preferably the new connector has some environmental protection and also a locking mechanism.

author: RobertHolcombe
author_rank: Frequent Contributor
timestamp: October 24, 2018, 04:30:16 am
content: Circular mil-spec connector meets your requirement but is potentially way overkill and expensive

author: rthorntn
author_rank: Frequent Contributor
timestamp: October 24, 2018, 07:33:30 am
content: Thanks, very similar parts to the Jaycar connector on DigiKey (5.5mm x 2.5mm & 5.5mm x 2.1mm) are 5A.

author: Gyro
author_rank: Super Contributor
timestamp: October 24, 2018, 09:03:51 am
content: The best type of barrel connectors are the ones with a forked inner connector (rather than a smooth barrel). The mating connector (chassis part) outer contact is a multi finger ring, rather than a single side contact (often actuating a switch). They almost universally have Yellow insulation, as used in laptops.These yellow ones are much higher rated than the ordinary ones. These are often rated for several amps, rather than the typical 500mA to 1A but even so, 12.5A would be way over the top.EDIT: XLR connectors are often rated quite high, Neutrik PowerCon even higher.

author: rsjsouza
author_rank: Super Contributor
timestamp: October 24, 2018, 09:30:27 am
content: I have some development boards that are rated for 7A on barrel jack connectors, and an old Alienware laptop sees 9A through a slightly larger one. Both have the spring contacts, not the smooth barrel.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: October 24, 2018, 12:04:25 pm
content: 4 pin Molex, 2 for each polarity; that's the common setup for hamradio transceivers which use to take about 20A