Reccomend a DC Electronic Load Box / Dummy Load for testing power supplies?

[outoftune]

After years of using high wattage power resistors, I'm considering upgrading to get a DC electronic load for using as a dummy load to test power supplies.

Most of the time I'm dealing with smaller PSU's based on LM317/337 and 78XX/79XX, but occasionally deal with some bigger console supplies putting out fairly high current (5A or higher at +/- 18VDC or +/-24VDC) and would like to be able to stress test these on the bench when I don't have the console to connect them to.

I've seen the kit from Five Fish studios which looks pretty neat for a DIY: https://fivefishstudios.com/diy/eload/

I'd also be open to just paying for a ready made product (new or used) that could work right away if the price is reasonable.

Any suggestions on devices to check out or kit's that can be built? Thanks.

 

[warpie]

I'm also interested. Sorry I can't help

 

[radardoug]

If you are only doing this occasionally, high wattage resistors are the way to go. Much cheaper.

 

[Bo Deadly]

Just thinking out loud here but you could just mount a couple of mosfets to a block of aluminum with a simple rectifier, capacitor and drain resistor sort of passive circuit and then drive it with a function generator. Meaning with no signal the mosfet gate is grounded and there's no load. But as you feed it signal from the function generator, that brings the gate up and turns the mosfet on loading the supply. And if you make the cap and drain resistor smallish, you could actually make an AC load to test AC load like for power amps. For dual supplies, the upper half rectifies the fn gen on positive swings and the lower half rectifies on negative swings so you should be able to load symetrically. The mosfets would not turn on linearly though. There would require more parts but very doable if desired.

 

[Whoops]

These modules are really nice, I have some PSU's made by this company same similar type of modules and I really like them.

https://i.imgur.com/UF8OLgSl.png

You also have a lot of different options on Ebay...

 

[volker]

I built this simple constant current load to test HV supplies. The way it works is the opamp will change its output so that the negative input matches the positive input. So by adjusting the input voltage the same voltage will be forced across the current sensing resistor R2, hence the equivalent current through the MOSFET.

The opamp should be a rail-to-rail type in order to be able to adjust to 0A, TLV271 for example. The MOSFET will carry most of the load, so the heatsink must be sized for it. Choose the maximum current you want to draw and calculate the wattage for R2 accordingly. For lower voltages and higher currents, 1R or even lower would be better suited.

 

[pucho812]

These modules are really nice, I have some PSU's made by this company same similar type of modules and I really like them.

https://i.imgur.com/UF8OLgSl.png

You also have a lot of different options on Ebay...

what company is that?

 

[Whoops]

what company is that?

I don't remember the name now, but if you go to EEVblog he has some videos about these modules sent by them for him to test

 

[abbey road d enfer]

Any suggestions on devices to check out or kit's that can be built? Thanks.

Beware that neither resistors nor active loads effectively represent the load that many electronic circuits present. In particular mixers, with their multitude of branches, result in an initial current kick that is often several times the steady-state draw.

 

[volker]

Beware that neither resistors nor active loads effectively represent the load that many electronic circuits present. In particular mixers, with their multitude of branches, result in an initial current kick that is often several times the steady-state draw.

It would be trivial to replace the pot in my circuit with some sort of voltage control. Microcontroller + DAC/digital pot and it's possible to use arbitrary load/time curves. Connect it to the computer and you can comfortably run any test you want.

 

[abbey road d enfer]

It would be trivial to replace the pot in my circuit with some sort of voltage control. Microcontroller + DAC/digital pot and it's possible to use arbitrary load/time curves. Connect it to the computer and you can comfortably run any test you want.

Hmmm... You would have to model the load, which is not trivial, and then need to sync the load behaviour with teh start of the PSU. It is certainly feasible, but not über simple.