Beginner power source - Page 1
Forum section: electronics / beginners

author: Groth
author_rank: Newbie
timestamp: April 08, 2016, 09:54:13 am
content: Hey guys. I'm almost a beginner and have been playing around with 5v stuff for a while, but now I'd like to do some stuff at 12v and 3v. I'm thinking it's time to buy a bench power supply, but I have no clue what to look for.My prioroties:Safe.At least 3-12v (DC).Cheap.If possible I'd also like current limiting function.Any suggestions on models and/or brands I should look for?

author: LA7SJA
author_rank: Regular Contributor
timestamp: April 08, 2016, 09:58:43 am
content: What country do you live in?Johan-Fredrik

author: Groth
author_rank: Newbie
timestamp: April 08, 2016, 10:00:52 am
content: Oh sorry, I should have mentioned that. I live in Sweden.

author: alexanderbrevig
author_rank: Frequent Contributor
timestamp: April 08, 2016, 10:14:09 am
content: Maybe something like:Skip transformer and use output from a laptop power block or something that gives you 16+ volts.Then add a current limiter at the end before C3 output:There are many variations on the LM317 variable power supply project. Good luck!

author: Groth
author_rank: Newbie
timestamp: April 08, 2016, 10:16:30 am
content: Thanks for the schematic, but I'm not quite ready to build my own yet. I'm avoiding the mains voltage side until I feel safe poking around there.

author: alexanderbrevig
author_rank: Frequent Contributor
timestamp: April 08, 2016, 10:49:02 am
content: Yes, that's why I said to omit itIf you want to buy something thenhttp://se.farnell.com/tenma/72-10480/power-supply-1ch-30v-3a-adjustable/dp/2251946?ost=72-10480&selectedCategoryId=&categoryId=700000005792is hard to beat.EDIT: hard to beat in terms of ability and price, easy to beat in terms of precision and features

author: rdl
author_rank: Super Contributor
timestamp: April 08, 2016, 11:01:35 am
content: That Tenma power supply is a re-badged Korad, and is a good choice in that price range. A quality brand, used power supply may be a better choice in that price range. In the US an Agilent E3610A is what I would look for, but things are probably very different in Sweden.

author: Groth
author_rank: Newbie
timestamp: April 08, 2016, 03:55:03 pm
content: Quote from: alexanderbrevig on April 08, 2016, 10:49:02 amSorry, I missed that.Quote from: alexanderbrevig on April 08, 2016, 10:49:02 amI'll be buying that. Later on I'll definitely look into the design you posted.Thanks for the help.

author: Ian.M
author_rank: Super Contributor
timestamp: April 08, 2016, 05:08:51 pm
content: Put the current limiter before the regulator (i.e. in series with the laptop PSU output) or it will seriously compromise the output voltage regulation.Also, you'll have problems finding an affordable low-ohm variable resistor for the current limiter that lets you get a reasonable output current range. e.g. if you use a 22R 5W wirewound pot, you need to keep the max current under approx 450mA to prevent it burning up, which means you need a 2R7 resistor in series with the pot, and at max resistance it will still pass approx 50mA. Therefore you may want a switch to bypass the current control, or even to switch in fixed resistors in place of the pot to allow a higher current limit e.g 1A. Both regulators will need a very good heatsink.

author: Groth
author_rank: Newbie
timestamp: April 08, 2016, 05:29:21 pm
content: Quote from: Ian.M on April 08, 2016, 05:08:51 pmI'm afraid this is a bit past my level currently. I'll get back to this topic when I've learned some more.

author: MarkF
author_rank: Super Contributor
timestamp: April 08, 2016, 07:39:41 pm
content: I have a coupleHP Agilent 6215A 0-25V 0-400mA Power Suppliesfrom eBay. They work very well for small projects that don't require massive amounts of current.Edit: Sorry missed that you're in Sweden.

author: LA7SJA
author_rank: Regular Contributor
timestamp: April 08, 2016, 08:58:44 pm
content: Thishttp://www.kjell.com/no/produkter/elektro-og-verktoy/stromforsyning/laboratoriestromforsyning/velleman-labstromforsyning-0-15-v-0-3-a-p44800should be easy to buy in Sweden here is a list of shops in Swedenhttp://www.kjell.com/se/butikerJohan-Fredrik

author: Groth
author_rank: Newbie
timestamp: April 08, 2016, 09:01:08 pm
content: Quote from: LA7SJA on April 08, 2016, 08:58:44 pmMy experience with Kjell&Co is that anything that is decent quality is much more expensive there than anywhere else. I used to work there btw.

author: LA7SJA
author_rank: Regular Contributor
timestamp: April 08, 2016, 09:12:47 pm
content: What is "Cheap"? I belive this to be cheap and it is ok quality and more than meets it's spec.Johan-Fredrik

author: Iwanushka
author_rank: Frequent Contributor
timestamp: April 08, 2016, 10:10:40 pm
content: Quote from: LA7SJA on April 08, 2016, 08:58:44 pmThese things use quite good design and are hard to kill, should be more than fine for the first PSU.