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Old 25th Feb 2021, 5:37 pm   #1
indiosse
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Default Load resistor on low voltage power supply

Hi all.

I have a few load resistors lying around.

I use them on DC power supplies, but am wondering if they would work on a low voltage AC power supply as well, say to test 0.5A on 19VAC supply.

Thanks
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Old 25th Feb 2021, 6:04 pm   #2
Station X
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Default Re: Load resistor on low voltage power supply

They'll work fine so long as they can handle the power. 8.5W in the example you quote, but obviously current and power will depend on the resistance.
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Old 25th Feb 2021, 6:29 pm   #3
Al (astral highway)
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Default Re: Load resistor on low voltage power supply

Quote:
Originally Posted by indiosse View Post

I have a few load resistors lying around.

I ... am wondering if they would work on a low voltage AC power supply as well, say to test 0.5A on 19VAC supply.

Sounds like this is from a simple transformer?


What do you want the test to establish? It may be productive to monitor voltage when that current is passing - if that's the current you will be needing. Depending on the relative size of the transformer, the volts may 'sag' at full current, so worth checking that.
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Old 26th Feb 2021, 10:44 am   #4
PsychMan
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Default Re: Load resistor on low voltage power supply

Also worth bearing in mind that they will work for you just as they do on DC supplies, but only for testing purely resistive loads.

If you're making an AC supply, perhaps you're looking to work with inductive loads, in which case the maths gets more complicated than simple ohms law.

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Old 26th Feb 2021, 5:06 pm   #5
merlinmaxwell
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Default Re: Load resistor on low voltage power supply

Quote:
the maths gets more complicated than simple ohms law.
The maths and arithmetic stay the same, it's the numbers that change from "simple" to "complex"*, any good scientific calculator will handle these. It is not hard at all, just a bit more long winded.

*complex numbers, not complex but A complex of two, just two, per number. Easy to see on graph paper, perhaps they should have been called graph or Cartesian (as in two dimensional) numbers.
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Old 27th Feb 2021, 10:34 am   #6
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Default Re: Load resistor on low voltage power supply

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Originally Posted by merlinmaxwell View Post
Easy to see on graph paper, perhaps they should have been called graph or Cartesian (as in two dimensional) numbers.
Rectangular form, as opposed to Polar form, sounds less intimidating than 'complex'.
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