Workbench USB power supply? - Page 1
Forum section: electronics / general

author: creyc
author_rank: Regular Contributor
timestamp: November 14, 2013, 03:13:05 am
content: Very often nowadays I'll need general USB power on the bench to power some new prototype, micro controller kit or piece of equipment. Usually I end up plugging into a USB port on my PC but I realize messing with experimental circuits I'm subjecting my computer to a bit of unnecessary risk when I don't need data.Recently I started using a regular USB power brick and a cheap 3' USB extension cord up to my work surface and this works pretty well. However I noticed (like others have always insisted!) USB power bricks are NOT created equal! A particular HTC adaptor has a very nasty transient and does not seem well regulated. My old iPod charger does a bit better, but I wondered what other folks around here do for USB power. Is there a power supply product that has USB built in? Do you use a USB breakout or possibly strip a USB cable and splice the power leads to a 5V fixed supply?I've also seen a few neat USB test/measurement products out there. I remember seeing a very cool USB current gauge somewhere but can't remember who did it. Also a USB-USB tap that let you pull series/parallel measurements easier.

author: SeanB
author_rank: Super Contributor
timestamp: November 14, 2013, 04:49:50 am
content: Buy a powered hub and use it as a charge /power source. I have a lovely 8 port USB1.0 hub which has a built in LDO 5V supply, and as soon as I get a wall wart that fits it it will become a USB charge station.

author: oldrose
author_rank: Contributor
timestamp: November 14, 2013, 08:00:06 am
content: How about an iPhone or iPad charger? Cheap, readily available. Or you could use a variety of android tablet or other mobile phone chargers for the same purpose. I defn. wouldn't use a PC's USB port for this sort of experimentation.

author: G7PSK
author_rank: Super Contributor
timestamp: November 14, 2013, 08:35:45 am
content: I have a powered usb hub combined wall wart that just sits in a power socket on my bench. Cant think why it was made that way as you need a usb cable to connect to a computer but it does have the 4 powered ports built into the wall wart.

author: mariush
author_rank: Super Contributor
timestamp: November 14, 2013, 11:34:47 am
content: Get a small power adapter or recycle one from an old scanner or something (7.5v 1a or something like that) and you get 5v from that using a cheap linear regulator.Then use a chip like Adum4160 or Adum3160 to isolate the data lines coming from the PC and you got yourself the perfect usb power supply. You'll get only 10mbps but that's enough for projects.You have here a schematic (and you can ignore the top power supply section if you use your own power supply):https://www.circuitsathome.com/wp/wp-content/uploads/2010/10/USB_Isolator_r10.pdf

author: amyk
author_rank: Super Contributor
timestamp: November 14, 2013, 11:52:38 am
content: How about a regular bench supply set to 5V (and possibly current limit 500mA)?(Before someone complains about it being too easy to let the magic smoke out, that's already a possibility if you're experimenting with any electronics using one...)

author: creyc
author_rank: Regular Contributor
timestamp: November 14, 2013, 12:49:15 pm
content: Here are a few things that caught my eye for USB bench power needs:Basic Wall Charger - 5V USB (1A)USB current meterUSB Tester by FriedCircuitsSparkFun Cerberus USB CableI'm not sure how well it works for data but for power this looks handy

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 14, 2013, 03:13:51 pm
content: What about an old PC?

author: creyc
author_rank: Regular Contributor
timestamp: November 14, 2013, 04:23:50 pm
content: Quote from: NiHaoMike on November 14, 2013, 03:13:51 pmMy lab computerisan old PC! Still, trying to prolong the lifetime of its USB ports.

author: AG6QR
author_rank: Frequent Contributor
timestamp: November 14, 2013, 05:39:00 pm
content: Two things I did:I took a short USB extension cable, cut it in half, and soldered stackable banana plugs to the power leads. This lets me plug the female half into a bench power supply to tweak the voltage and monitor the current. Or I have the option to connect the two halves together, inserting an ammeter in series and/or a voltmeter in parallel to monitor voltage and current, while grabbing power from any USB supply.Besides my adjustable bench power supplies, I've got a fixed 13.8V linear supply that feeds a couple of cigarette lighter style outlets and Anderson Power poles. I've made a 7805 based regulator to regulate 12V from the power poles down to 5V on a pair of USB sockets. It uses a large heat sink, isn't very efficient, and isn't capable of large current, but it gives a very clean 5V. Plus it's cheap and nearly indestructible.