Kensington and iGo Universal Power Supply Hacking - Page 1
Forum section: electronics / projects

author: Jon Chandler
author_rank: Frequent Contributor
timestamp: May 04, 2012, 06:10:35 pm
content: Kensington and iGo both make universal power supplies that can be used to power various devices using special tips to configure voltage and current settings. I've often wondered if these could be hacked to use as lab supplies. A recent find of a Kensington 70 watt supply led me to do some experimenting.I'm happy to report that both of these power supplies can be used as low-cost bench power supplies with adjustable voltage and current limiting. The Kensington types in particular are great building blocks for simple knob(pot)-controlled to more featured microprocessor-controlled supplies.Kensington supplies provide 0 - 25 volt outputs at up to 6 amps. Voltage and current are each controlled by a pair of resistors in a voltage divider arrangement. A digital pot or DAC output can easily control these supplies.iGo makes two types of supplies - a laptop supply and an "accessory" supply. The second is what I experimented with. It's more limited with a 3.1 - 9 volt range at up to 1.5 amps. Voltage and current are each controlled with a single resistor.The details can be seen here:Kensington SuppliesiGo SuppliesEither type of supply can be bought new for $15 or less. Add a few parts and you can have a nice bench supply.

author: T4P
author_rank: Super Contributor
timestamp: May 04, 2012, 06:44:41 pm
content: Hmm, i'll try and find one of them in my cityMan, kensington no longer sells them so no go.If anyone is willing to sell me one, i'm all up.

author: terabyte
author_rank: Contributor
timestamp: May 05, 2012, 08:50:50 pm
content: I dug up an old Belkin Universal Adapter I had and it was identical right down to the pin-out of the connector. These instructions worked beautifully. Unfortunately I killed a component whilst trying to tear it apart. Can someone help me figure out what the little coil next to the mains inlet labeled 470 is? I want to try my hand at replacing it.Says made in the USA!!!In this pic you can see the component I broke;BigER pics here;http://www.flickr.com/photos/thespeedphreak/sets/72157629973057051/

author: terabyte
author_rank: Contributor
timestamp: May 05, 2012, 09:11:33 pm
content: Quote from: Dave.S on May 04, 2012, 06:44:41 pmHere you go Dave. I just ordered 2 for myself.http://www.overstock.com/Electronics/Kensington-33336-Wall-Ultra-Portable-Notebook-Power-Adapter/2628463/product.html

author: sonicj
author_rank: Frequent Contributor
timestamp: May 05, 2012, 09:23:45 pm
content: i made something similar out of a targus 90w supply a while back. its adjustable from 15 - 24V, but i don't recall pins for current. i'll have to take another look....-sj

author: T4P
author_rank: Super Contributor
timestamp: May 05, 2012, 09:33:36 pm
content: Quote from: terabyte on May 05, 2012, 09:11:33 pmSend me a message. How much did you pay for it?

author: terabyte
author_rank: Contributor
timestamp: May 05, 2012, 10:12:29 pm
content: Sorry I meant to post the link;http://www.overstock.com/Electronics/Kensington-33336-Wall-Ultra-Portable-Notebook-Power-Adapter/2628463/product.htmlI paid $35 for 2 shipped to my door.

author: G7PSK
author_rank: Super Contributor
timestamp: May 05, 2012, 10:15:11 pm
content: Quote from: terabyte on May 05, 2012, 08:50:50 pmIts just an inductance or choke if you are old like me. 470 micro Henry I would think.

author: terabyte
author_rank: Contributor
timestamp: May 05, 2012, 10:36:33 pm
content: Quote from: G7PSK on May 05, 2012, 10:15:11 pmThank you sir.

author: Jon Chandler
author_rank: Frequent Contributor
timestamp: May 06, 2012, 06:18:54 am
content: I've heard these things are pretty fragile when out of the case. I'm going to leave it intact and connect it via the cable.

author: terabyte
author_rank: Contributor
timestamp: May 06, 2012, 07:08:27 am
content: its pretty much useless outside of its casefragile is an understatement

author: george graves
author_rank: Super Contributor
timestamp: May 06, 2012, 08:39:19 am
content: Whats with all the ICs?

author: SeanB
author_rank: Super Contributor
timestamp: May 06, 2012, 09:21:13 am
content: Those are active switches, used to improve conversion efficiency by removing the diode drop. Nice PCB planar transformers there, that board must be multilayered, 12 at least, to get the primary side small enough to fit in the layering under the ferrite caps.

author: george graves
author_rank: Super Contributor
timestamp: May 06, 2012, 09:24:09 am
content: 12 layer ?I'm wondering if it would be a good starting point for a programmable power supply.

author: Jon Chandler
author_rank: Frequent Contributor
timestamp: May 06, 2012, 05:32:53 pm
content: Quote from: george graves on May 06, 2012, 09:24:09 amUmmm...what can I say....wait, I already did!Quote from: Jon Chandler on May 04, 2012, 06:10:35 pm

author: terabyte
author_rank: Contributor
timestamp: May 16, 2012, 06:13:50 pm
content: Quote from: terabyte on May 05, 2012, 10:12:29 pmThese came in and they worked a treat. Same coloring on all the wires. With no load @ 24V and a short going through the Fluke 87V I got a hair over 7Amps, it got pretty warm and you could hear the high frequency switching very clearly whilst doing do.

author: MikeK
author_rank: Super Contributor
timestamp: May 16, 2012, 06:40:33 pm
content: Good thread. I just bought one of these to fool around with.

author: DaveAvr
author_rank: Newbie
timestamp: May 17, 2012, 05:53:12 pm
content: I've been messing around with these thing for a couple of years now. I've opened three of them to build programmable supplies. All three are now dead two because some random wire on my bench would fall into the board and make it pop. One mechanic while breaking open the case. There are a couple of very good reasons for getting them opened however. One is they cool much better. I added a heat sink were they ran hot. In there case you will find that they start to shut down due to heat if run at full power for a long time. The other advantage to getting inside there is that there is a continues 12V available (approximately) that is nice for running your programmable supply electronics. You'll find that voltage near the 12V input connector.So there you go. Good Luck. If you are careful and don't make the same dumb mistakes I made you can gain something by breaking one open. But don't blame me if it breaks.Cheers,DaveP.S. If some one needs a part contact me I have spares.

author: terabyte
author_rank: Contributor
timestamp: May 18, 2012, 01:52:21 am
content: Quote from: DaveAvr on May 17, 2012, 05:53:12 pmTHanks for sharing.DaveAVR where are you located? I need one of those 470 mH chokes on the inlet side of things.

author: DaveAvr
author_rank: Newbie
timestamp: May 18, 2012, 01:05:37 pm
content: terabyte - Contact me with a private message and your address and I'll drop one in the mail. You can buy me a beer next time your in Oregon. - Cheers, DaveAvr

author: krivx
author_rank: Frequent Contributor
timestamp: May 18, 2012, 01:37:10 pm
content: Has anyone made any measurements on the outputs? I'm curious about the quality of the regulation, switching noise etc.

author: MikeK
author_rank: Super Contributor
timestamp: May 24, 2012, 03:40:30 am
content: Quote from: krivx on May 18, 2012, 01:37:10 pmMine arrived today. Here's a no-load scope trace before I go to bed.

author: IanB
author_rank: Super Contributor
timestamp: May 26, 2012, 01:01:43 am
content: I got a few of these from overstock.com to experiment with.The ones that actually arrived were model number 38004. It says 120 W max on the case, but 90 W continuous in the specifications. I guess there are 30 extra marketing watts thrown in for good measure.I don't see an obvious way to open it. Any hints? Is the case welded shut?

author: MikeK
author_rank: Super Contributor
timestamp: May 26, 2012, 01:16:12 am
content: The shiny top panel is held on with strong sticky tape.

author: MikeK
author_rank: Super Contributor
timestamp: May 26, 2012, 01:21:55 am
content: Okay, that appears to be a ruse. I got it off and no screws underneath.

author: MikeK
author_rank: Super Contributor
timestamp: May 26, 2012, 01:32:42 am
content: Yeah, I think it's welded. If I twist the case I can't even get it to make a creak.

author: T4P
author_rank: Super Contributor
timestamp: May 26, 2012, 03:42:30 am
content: Quote from: MikeK on May 26, 2012, 01:32:42 amBring out the dremel !

author: terabyte
author_rank: Contributor
timestamp: May 26, 2012, 04:49:41 pm
content: I recommend you leave it alone. Taking it apart without damage is quite difficult. This is experience talking

author: george graves
author_rank: Super Contributor
timestamp: May 27, 2012, 01:18:21 am
content: That's why I plan on buying 2 or 3. There's got to be an easy way to get them apart? no?

author: MikeK
author_rank: Super Contributor
timestamp: May 27, 2012, 01:43:48 am
content: Quote from: george graves on May 27, 2012, 01:18:21 amNo, there doesn't have to be. Most wall warts are molded, for the same reason: nobody needs to take them apart. Almost any case you can disassemble you would hear creaking when you twist it, but this makes no noise. So it's very likely plastic-welded. But nothing a heated X-acto knife can't remedy. I also have a small milling machine that I could clamp it to and carefully slice it open with a thin saw blade.

author: george graves
author_rank: Super Contributor
timestamp: May 27, 2012, 01:57:10 am
content: Well - there ya go. Told you there's got to be an easy way.

author: T4P
author_rank: Super Contributor
timestamp: May 27, 2012, 02:51:48 pm
content: I tore open wall warts either using a pocket saw ( it's called that but it's not exactly pocket friendly is it ? ) or my "dremel" with the saw bit ...