I have built a modular power supply - and I was wondering if such thing exists to generate a mock load.
I have two supply blocks and I need to make sure they are supplying adequate current. I can hook up a multimeter to check current fine but that only works if something is pulling it.
Could I build something using an old speaker coil? This is for a 12V power supply.
Electronic loads are common pieces of test instrumentation. Typically you can program or control them to alter the load current with time so the PSU can be tested for regulation, overshoot, undershoot etc. They're also useful for discharge testing of batteries. You can typically set them for constant current, constant resistance or constant wattage. Asian branded ones start at a few hundred dollars. They tend to have noisy fans since they have to dissipate a lot of heat.
Hobbyist grade loads are also available from the usual sources for tens of dollars.
For simple DIY testing a few resistors (possibly switched with a MOSFET) can do a lot. Like this 1\$\Omega\$ 300W resistor.
A full test rack suitable for fully testing a desktop computer power supply could be a few hundred thousand dollars (link to YT video).
I've even used automobile headlamp incandescent bulbs.
"Active loads" are often used to test supplies for linear and step load responses.
The simplest might be a suitable NPN power transistor load with small emitter resistor for 50 mV current shunts. Emitter R's also serve to normalize the variation of emitter resistance due to production tolerances with hFE. They must be on a common heatsink to prevent thermal runaway.
Current and voltage sensing in a servo loop allows controlled loads to be regulated with DAC or potentiometer controls.
https://wiki.analog.com/university/courses/tutorials/alm-active-loads
I find you get the best watts per dollar buying 5 W ceramic wirewound resistors that mount in free air.
The upside is that they're light and don't need a separate heatsink, and you can switch them to get finely controlled resistance.
The downside being that you need a lot of them to shift any serious power, and they need an adequately ventilated mounting volume to allow cooling. But air is cheaper than the large heatsinks needed by alli-clad power resistors.
Pro tip - a 3 kW electric kettle is about 20 ohms (240 V land), and can dissipate 3 kW when water-cooled. You could probably borrow a few from friends and neighbours if you wanted a lower resistance for a short test.
