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opinions on variable power supply

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johnlouie

New Member
Hi all,

I'm new to this forum, and haven't touched a soldering iron or breadboard in many a year, but recently saw some parts on Ebay and now I'm getting back into the hobby that I loved as a teenager (20+ yrs ago).

A quick question for the more experienced: I saw a digital variable power supply for around $75, that can provide 0-18V and 0-3 Amps. I've seen higher voltage and amperage models, but I was thinking that most of what I would make would run off batteries eventually.

any opinions on 18V or higher and the brand OTE?

thanks in advance,
John Louie
 

hamfiles

New Member
75 bucks is a good deal, IMHO.

You might be able to build one for a little less. Link below shows a good dual voltage regulator. Shows how to make it fixed, or variable by changing R2 and R4 to a dual ganged 5k potentiometer.

**broken link removed**

I built my first regulator w/ LM 317 years ago, and it still works very well.

If you need more current, you can substitute the 317 with the LM 338 in the above link. The 338 is a 5 amp regulator. With the LM 338 substituted in, all connections and all other components are exactly the same. ref: http://www.electro-tech-online.com/custompdfs/2003/05/LM138.pdf for more info.


This ham radio club link also has a tutorial on voltage regulator circuits:

**broken link removed**

Not everyone is comfortable building a power supply, but its a good way to learn and gain experience.
 

johnlouie

New Member
first things first

thanks for all the links and opinions.

I recall being frustrated back as a teenager when I didn't have the right power source for a project. Memories of taping together endless D size batteries come to mind. :oops: So I thought that now that I can spend a little more money on this hobby, I'd get a nice variable power supply.

With all the other things that could possibly go wrong in building a circuit, its nice to remove the power as an X factor. I did once make a simple AC to DC converter, but given the relative danger of an AC project, I'll hold off on that one for a little while.

This is a great resource. I can't wait to get the parts in the mail and build some of the projects here.

ps. I found a cheap 8-20v 200mA power supply on Ebay that I'll use for now. Actually it was a set of 4 of them.

thanks again
John Louie
 

Dean Huster

Well-Known Member
Variable supplies

I've been messing around with this hobby since around 1962 and used to think that I had to have a variable supply ... then a variable supply that would go all the way to zero volts and up to infinity ... then a bi-polar variable supply ... then a triple supply .... etc. However, the only times that I've really needed a variable supply were for theory experiments rather than a practical application. When working with nearly any digital or analog project, I've been very happy with fixed +5, +12 and -12 volt supplies. If I were building by own box, I'd have a raw supply with plenty of overhead and then run several fixed supplies, preferably cascading them so that the lower-voltage regulators don't have to bear the high overhead. Then I'd run bipolar sets for ±5, ±9, ±12, ±15, ±18 and ±24 volts. Plenty of capability, low cost and no frills.

Dean
 

Madmartin

New Member
I don't suppose you to rip devices and stuff for getting your parts,
but bear in mind that some neat devices (relays, coils, etc.) work from
a more industrial-style 24V DC. So I would prefer the 0-30V 0-3A style.

But if you just want to get back to a few circuits, just for fun. There you go.
With 75 bucks, that would not even be to expensive, mine once cost over a 120 bucks ! Be sure that its output is short-circuit protected and
if possible this short-circuit protection can be regulated.

You might upgrade later, if you really need to or even get other power supplies then.
 
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