Variable DC Power Supply - Which one?

[KapHn8d]

fwiw, I picked up this one and haven't had issues so far, but I'm new to the hobby, so the limits of my skill are vast and I'm not a good representative sample: Mastech HY3005F-3Triple Linear DC Power Supply, 30V, 5A: Amazon.com: Industrial & Scientific

 

[jmgallego]

fwiw, I picked up this one and haven't had issues so far, but I'm new to the hobby, so the limits of my skill are vast and I'm not a good representative sample: Mastech HY3005F-3Triple Linear DC Power Supply, 30V, 5A: Amazon.com: Industrial & Scientific

That one looks more economically doable for me. Thanks for the tip... :yh:

 

[jmgallego]

Just get a cheap-ass one from China and build your own current regulators from transistors and your own circuits. Then you have ultimate control over your output and if you burn out your power supply, or it malfunctions, you won't affect your stuff.

I bought this one, but I'd probably buy some cheaper smaller ones if I knew what I know know. When I want to regulate current in a precise manner I just use a simple MOSFET based current regulator. If I were worried about the voltage stability I'd just put a linear regulator before it. All these secondary components are super cheap and do a great job.

That looks even more doable!! Also, your suggestions make sense. As I mention on the original post, I am looking to an inexpensive one to test new laser diodes. But "we" are getting quite close to the 5A range, remember when we broke the 1A to drive our little babies? :yh:

Thanks guys for the great input.

 

[Zeebit]

Gonna try and make my own bench PS. How much ripple is acceptable for general use?

 

[The Lightning Stalker]

You could probably get away with ~30mV for everything except audio circuits, though it may trip up the
digital junk. For audio, <1mV.

 

[Zeebit]

So if a 3A PS is going to have a ripple of 30mV(p-p) its going to take 0.8F of smoothing caps. That is a lot. Am I missing something?

 

[The Lightning Stalker]

No. That sounds about right for a 60Hz supply that has no active regulation.

 

[Zeebit]

Here is the PS I am planning to build: (thanks to djQUAN) http://www.quan-diy.com/projects/benchps/benchps.htm

I will be limiting it to 3A only.

So how much capacitance is needed for a capacitor (only) filter?

 

[djQUAN]

It's already regulated. What do you need the capacitor for?

Or are you asking about the bridge rectifier / capacitor before that circuit?

 

[Zeebit]

I am talking about the caps after the bridge rectifier.

 

[djQUAN]

I just used two 2200uF caps in parallel. Less could still have worked fine.

 

[Zeebit]

Ah thanks. I was starting to think that I would need a bunch of 10000uF caps. Turns out even one will work.

Btw, you've got mail. I'm not trying to rush you because I know you're at work.

I'll rep you when I can.



For everyone else, sorry for derailing the thread.

 

[The Lightning Stalker]

I believe the one in the pictures uses a single 5600μF capacitor.