Author Topic: Any good variable DC power supplies?  (Read 1079 times)

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Offline vipulan12Topic starter

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Any good variable DC power supplies?
« on: July 21, 2013, 07:51:05 PM »
any anyone recommend me a Variable DC power supply?

i need one the can range from 0-100V DC
under 100 dollars hopefully?

i just want to use it for simple prototyping purposes
if there are any other features i should know about please let me know

Offline jwatte

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Re: Any good variable DC power supplies?
« Reply #1 on: July 21, 2013, 08:40:27 PM »
I have one that does either two channels of 0-30V/5A, or one of 0-30V/10A, or one of 0-60V/5A. It was $250, and it's a Chinese brand; I see it's now $250 on Amazon: http://www.amazon.com/gp/product/B004ISD7T6/ref=as_li_ss_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B004ISD7T6&linkCode=as2&tag=enchage-20

I think going to 100V is likely to be hard to get affordably. There aren't many "hobby" uses for that kind of voltage. Also, the safety needs for DC start becoming troublesome for "hobby"use over the 48V range (and, in fact, is already somewhat marginal at that point.)

Why do you really need more than 30V? or 50V? You can get 36V for about $130: http://rcm-na.amazon-adsystem.com/e/cm?lt1=_blank&bc1=000000&IS2=1&bg1=FFFFFF&fc1=000000&lc1=0000FF&t=enchage-20&o=1&p=8&l=as4&m=amazon&f=ifr&ref=ss_til&asins=B002BXI8PS

Or eBay, 30V, 5A: http://www.ebay.com/itm/30V-5A-110V-Precision-Variable-DC-Power-Supply-w-Clip-Cable-Digital-Adjustable-/300882516942?pt=LH_DefaultDomain_0&hash=item460dfedbce

If you need to go higher on a budget, you probably have to build it yourself. Note that regulators (components) that can take > 35V in are harder to find and more expensive, too, which may be why many power supplies only go to 30V.

Also, how many amps do you need?


Offline vipulan12Topic starter

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Re: Any good variable DC power supplies?
« Reply #2 on: July 22, 2013, 02:13:53 PM »
well, seeing how the circuit draws the current the more the better but they seem too expensive

Offline jwatte

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Re: Any good variable DC power supplies?
« Reply #3 on: July 22, 2013, 04:31:31 PM »
So, the most affordable is 18V/3A. The next level is 30V/5A. The next level is 60V/5A (or 30V/10A.) After that, it goes up really quickly.
This is because of the complexities of designing high-voltage solutions.

So, why do you need 100V? Why is 18V not enough? Or 30V? Or 60V?

Offline vipulan12Topic starter

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Re: Any good variable DC power supplies?
« Reply #4 on: July 23, 2013, 02:35:34 PM »
well i thought it would be better to have a large range of voltages so that when i need them i could use them

Offline jwatte

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Re: Any good variable DC power supplies?
« Reply #5 on: July 24, 2013, 10:34:23 AM »
Quote
i thought it would be better to have a large range of voltages so that when i need them i could use them

Yes, it is! And it's also a significant factor in cost! Engineering is about trade-offs. For basic hobby use, a 3A/18V supply for $60 might be just fine, although if you can step up to something slightly bigger that'll probably keep being fine for longer.
Also, if you're using robots with significant current draw (many servos, or electric motors) then even a 5A power supply is not enough to power such a robot -- typically you will parallel the power supply with a battery pack, so the battery pack can provide high current when needed, and "float" back to a reasonable voltage when current draw is low.

Offline waltr

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Re: Any good variable DC power supplies?
« Reply #6 on: July 24, 2013, 11:46:52 AM »
I find with experimenting that many times I need more than one PS. So I have PS's that do:
5V @ 1A (for general logic circuits)
9V @ 1.5A Wall warts to power circuits that have regulators on board
12V @ 500mA Wall warts
0 to 15V @1A GP adjustable
+/- 0 to 25V @ 0.5A (for op-amps and other analog circuits that require two rail Voltages)
13.5V @ 10A (Pb acid battery substitute)
Plus will use 12V, 9V, and AA series batteries as needed.

Only the adjustable dual Voltage supply seemed expensive (>$100).
I built the 5V, 1A which uses an LM7805.
and the 0-15V which uses an LM317.

My point is that there isn't just one power supply that does it all.
Another pint is that, it is not a great idea to use a supply that can deliver 100V on a circuit that has a max of 5.5V. It is just too easy to turn the adjustment too high and let all the magic smoke out of the chips in your circuit.
That is another reason I use LM7805 type supplies, they have 1A max current and a fixed output Voltage.

 


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