Beginner power source

[Groth]

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?

[LA7SJA]

What country do you live in?

Johan-Fredrik

[Groth]

Oh sorry, I should have mentioned that. I live in Sweden.

[alexanderbrevig]

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!

[Groth]

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.

[alexanderbrevig]

Yes, that's why I said to omit it



If you want to buy something then http://se.farnell.com/tenma/72-10480/power-supply-1ch-30v-3a-adjustable/dp/2251946?ost=72-10480&selectedCategoryId=&categoryId=700000005792 is hard to beat.
EDIT: hard to beat in terms of ability and price, easy to beat in terms of precision and features

[rdl]

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.

[Groth]

Yes, that's why I said to omit it

Sorry, I missed that. 

If you want to buy something then http://se.farnell.com/tenma/72-10480/power-supply-1ch-30v-3a-adjustable/dp/2251946?ost=72-10480&selectedCategoryId=&categoryId=700000005792 is hard to beat.
EDIT: hard to beat in terms of ability and price, easy to beat in terms of precision and features

I'll be buying that. Later on I'll definitely look into the design you posted.

Thanks for the help.

[Ian.M]

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.

[Groth]

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.

I'm afraid this is a bit past my level currently. I'll get back to this topic when I've learned some more.

[MarkF]

I have a couple HP Agilent 6215A 0-25V 0-400mA Power Supplies from eBay.  They work very well for small projects that don't require massive amounts of current.


Edit:  Sorry missed that you're in Sweden.

[LA7SJA]

This http://www.kjell.com/no/produkter/elektro-og-verktoy/stromforsyning/laboratoriestromforsyning/velleman-labstromforsyning-0-15-v-0-3-a-p44800 should be easy to buy in Sweden here is a list of shops in Sweden http://www.kjell.com/se/butiker

Johan-Fredrik

[Groth]

This http://www.kjell.com/no/produkter/elektro-og-verktoy/stromforsyning/laboratoriestromforsyning/velleman-labstromforsyning-0-15-v-0-3-a-p44800 should be easy to buy in Sweden here is a list of shops in Sweden http://www.kjell.com/se/butiker

Johan-Fredrik

My 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.

[LA7SJA]

What is "Cheap"? I belive this to be cheap and it is ok quality and more than meets it's spec.

Johan-Fredrik

[Iwanushka]

This http://www.kjell.com/no/produkter/elektro-og-verktoy/stromforsyning/laboratoriestromforsyning/velleman-labstromforsyning-0-15-v-0-3-a-p44800 should be easy to buy in Sweden here is a list of shops in Sweden http://www.kjell.com/se/butiker

Johan-Fredrik

These things use quite good design and are hard to kill, should be more than fine for the first PSU.