[sdiy] Load testing dual PSU

Rob Spencer Rob at gmsn.co.uk
Mon Nov 3 18:54:02 CET 2014


I'm having a look at these resistors and weighing the costs...

10 individual 2 ohm 20W are about £2 each.
1 variable 47 ohm 100W is £22.

I'm tempted just to get the variable one and connect a meter up. This way I can ramp the current up with out having to switch off, plug in next resistor, then switch back on.

Cheers

Rob

> On 3 Nov 2014, at 15:28, blacet at blacet.com wrote:
> 
> A few calculations with Ohms law will do the trick. R=EI
> 
> W=EI will give you the minimum resistor wattage. I tend to use cheap ones
> from Mouser in the white ceramic housings. I also use 2X the minimum power
> to avoid them getting really hot.
> 
> I will string a few of them together as required to get the necessary ohms
> and watts.
> 
> 
> 
>> Hi Roman,
>> 
>> Thanks for the confirmation. In fairness I probably just need to get some
>> higher power resistors. For some reason I had it in my head that they
>> would be hugely expensive. I think I was picturing massive heavy ones that
>> I remember from college. I'm sure they aren't as expensive as I thought.
>> 
>> P.S. Friend request sent. I'd like to see the photos of that's okay.
>> 
>> Cheers
>> 
>> Rob
>> 
>>> On 3 Nov 2014, at 12:49, Roman Sowa <modular at go2.pl> wrote:
>>> 
>>> hi,
>>> actually I use both :)
>>> A string of 1 ohm 20W resistors, about 15 of them, so I can adjust load
>>> resistance with banana cable by clamping part of the string. And there
>>> is also G4 socket with soldered across part of the ladder, so I can see
>>> if there's heavy current flowing or not witout looking at power supply
>>> Amp meter. This is usable when testing switching circuits. I plug there
>>> 5W, 10W or 20W bulb depending on needed load capacity.
>>> 
>>> It get's hot, no matter what you do, just learn to live with that. Not
>>> really pssssst hot, the resistors get nicely warm/hot after some time at
>>> 3A.
>>> 
>>> Your temperatures will stabilize in manner of minutes, not days, so
>>> unless you are doing burn-in test, there's no need to leave it on for so
>>> long.
>>> 
>>> Roman
>>> 
>>> PS for my Facebook friends, few hours ago I posted a picture with the
>>> load fixture described here.
>>> 
>>> 
>>> 
>>> W dniu 2014-11-03 13:24, Rob Spencer pisze:
>>>> Hi,
>>>> 
>>>> I've recently developed a +-12v PSU, with +5v and post voltage
>>>> protection and am looking to do some load testing. I know I could
>>>> stick a low resistance across it but that's going to get very hot
>>>> very quickly. The other thing I'm thinking is to place some 12v light
>>>> bulbs across the rails and leave it running for a few days with
>>>> temperature monitoring in place on the voltage regulators.
>>>> 
>>>> I'm wondering how other people have tackled this in the past.
>>>> 
>>>> Cheers
>>>> 
>>>> Rob _______________________________________________ Synth-diy mailing
>>>> list Synth-diy at synth-diy.org
>>>> http://synth-diy.org/mailman/listinfo/synth-diy
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