Electronics > Beginners
Load at the output of a power supply board
Yac:
Hello everybody,
I have to set up a test bench to test two power supply boards, the first one provides a voltage of 24V (50W) and 48V (200W) and the second one provides a 5V (65W), +12V(7W) and -12V (7W).
I have to measure these voltages with a voltmeter at nominal load.
So, what load can I put on each output ?
Should I use a thermal radiator ? If so, how to choose the type of radiator.
Thank you in advance.
ledtester:
--- Quote from: Yac on September 03, 2019, 06:21:19 am ---So, what load can I put on each output ?
--- End quote ---
Usually DC power supplies are tested with an electronic load.
Otherwise any resistive load will work, such as power resistors and incandescent lamps.
Given the voltage and nominal wattage of a power supply, do you know how to compute the resistance required to draw the nominal power?
Yac:
Thank you for your help.
An electric load is a little expensive for what I want to do.
To calculate the resistance value I think it is necessary to use the ohm law.
But I don't know if the resistance will heat up a lot and if I have to use a heat sink to dissipate the heat.
For example, for the 48V output, I have a current of 4.2A, if I use a power resistor of 12 Ohms, 200W, Do I need a heat sink ?
ledtester:
--- Quote from: Yac on September 03, 2019, 07:16:45 pm ---An electric load is a little expensive for what I want to do.
--- End quote ---
You can get inexpensive electronic loads circuits on ebay/aliexpress.
This is a good one that works up to 30V and meets its advertized specs:
https://www.aliexpress.com/item/32776310672.html
This is another popular one which works at higher voltages, but you'll need to get two to test your 42V, 200W supply:
https://www.aliexpress.com/item/32916595565.html
--- Quote ---For example, for the 48V output, I have a current of 4.2A, if I use a power resistor of 12 Ohms, 200W, Do I need a heat sink ?
--- End quote ---
A power resistor is a resistor mounted on a heat sink. If the resistor is rated for 200W then there shouldn't be any problem.
How long do you have to test the supplies for? The power rating on a resistor is for continuous use. If you are only connecting the power supply for a short time you can get by with a lower rated resistor.
Yac:
Thank you for these ideas
The tests must be done automatically, I think these loads are not appropriated because I have to control the measuring devices via ethernet.
In fact, I don't know how long the tests will last, so I can't take the risk of choosing a lower rated resistor.
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