Lab Power Supplies

[vdi_nenna]

Can anyone recommend a testing power supply with at least 30v output?
I've seen some on the net but don't know if they are safe.

 

[Garyepe]

Can anyone recommend a testing power supply with at least 30v output?
I've seen some on the net but don't know if they are safe.

You can done business by paypal.
it is the savest payment method .

 

[vdi_nenna]

Sorry, I wasn't clear on what I meant to say.

Are they safe electronically as they seem not very costly. I imagined they would cost much more than the prices I see on the internet.

So if I buy a low-end power supply, will it work safely?
Anyone have experince with these?

See example:
http://www.a1parts.com/tequipment/power.htm

 

[Glowbug]

http://surplussales.com/PowerSupplies/PowerS-5.html

They always seem to have cool stuff 🙂

Honestly, if I was in the market for an adjustable PSU, I'd probably wait to see when the next hamfest was...you can usually find great deals on older test gear.

 

[Hardi]

So if I buy a low-end power supply, will it work safely?

As long as you don´t stress them near their maximum current capability...maybe.
Most of the cheap supplies die when you take high current for longer time due to small heat sinks and undersized parts.

 

[AndrewT]

I have used a few Lab Power Supplies.
I have never had a reliability issue.
My present one is a rebranded version (RS) of a well known make that I bought secondhand.
It is 2channel with adjustable voltage and adjustable current. The supplies can be used independently or series (with tracking) for 60Vdc or +-30Vdc or two @ 30Vdc.
You can hear the relays switching as the voltage is adjusted to minimise heat dissipation on the output devices. It has a fixed 5Vdc as well. The current limit can be adjusted from ~10mA to 2000mA

 

[star882]

It's surprisingly easy to build your own.

 

[vdi_nenna]

It's surprisingly easy to build your own.

Once that can do 30v and 20 amps?

 

[Hardi]

Once that can do 30v and 20 amps?

I think so. But parts alone will be more expensive than a (used) professional supply.

 

[dangus]

See my post in this thread, if you're into building a supply. Once you've got the regulator, the rest isn't hard. Transformer, caps and rectifiers could come from a junked hifi receiver.
http://www.diyaudio.com/forums/showthread.php?p=956942

Here's a working link to the MC1466 data sheet:
http://www.datasheetarchive.com/pdf-datasheets/datasheets-21/dsa-409990.pdf

[edit]
20 amps???!!! Doing that with a linear supply will be interesting... big transformer, big caps, lots of power transistors.

 

[AndrewT]

........... the rest isn't hard. Transformer, caps and rectifiers could come from a junked hifi receiver.
...............
20 amps???!!! Doing that with a linear supply will be interesting... big transformer, big caps, lots of power transistors.

and what about dissipation when the output voltage is <<30Vdc?

A multi tapped transformer is virtually obligatory for a linear supply.

 

[star882]

A low voltage buck converter is pretty easy to build. And no high voltages after the transformer so it is very good for beginners.

 

[AndrewT]

A low voltage buck converter is pretty easy to build. And no high voltages after the transformer so it is very good for beginners.

I've seen some on the net but don't know if they are safe.

 

[Bakmeel]

Does it have to be the cheapest of the line?

I've been using Delta Power Supplies for years in the lab and I'm convinced they are the best... not the cheapest though....

They'll last you a lifetime... I have an oldie at home. (30V / 10A) linear jobbie. Weighs a ton, but still works beautifully after 20+ years

 

[DRC]

Buy a secondhand one made by a good manufacturer. Unless you want very high power stick to linear designs.

dave

 

[star882]

I've seen some on the net but don't know if they are safe.

Start with something very low power, like step down a 9v battery to 5v or 3.3v. Such a low power circuit is very safe to handle.

Unless you want very high power stick to linear designs.

Switching regulators have become much cheaper than in the past. You'll really want switching for any significant amount of power as the thermal dissipation of a linear becomes prohibitive at higher powers. In modern commercial equipment, I have seen linear only used up to about 2w or so, except LDO which is still used at higher powers as thermal dissipation is still manageable. Above that and switching is the regulator of choice. In fact, given the very low cost of switching regulator circuits, the break even point where a switcher would be cheaper is surprisingly low and continues to fall.

Note that a low voltage buck converter is only slightly more difficult to design than a linear. And it is a good learning tool for beginners. My first switcher was based on a National Semiconductor switcher-on-a-chip and I used it as my bench power supply for a few years. To give you an idea of how easy it is to build it, I built it in 5th grade. It worked perfectly the first time I turned it on.