Need to check this out, the first test I did was with 8 diodes, then I started to ditch one by one, until the output voltage reached 4,5V, I could have messed this up, because I was using a 1Ohm resistor, so at 4,7A it would have 4,7V across it.
Better going down to 0.1Ω when you get up to those currents. Using my 20A test load as an example, a 6 diode setting would produce a drop of somewhere around 4.2V across the diodes. Add the 4.7V across your 1Ω shunt and your driver now needs to output 8.9V. A 0.1Ω shunt drops that down to 4.67V. My test load uses 8x 20A (4 sets of two for 4 different adjustable ranges) rectifier diodes and 100W 0.1Ω shunt, will sit and do 20A all day with the cooling fan on set to full voltage drop.
I grabbed a 0,68Ohms resistor and tried again with 6 diodes, since I didn't have 6A+ diodes, I had to put the dummy load under water to keep it cool. To generate the PWM, I used a Arduino Mega doing a sweep from 0 to 100% at frequencies of 490Hz and 980Hz.
Easiest to stick to 0.1/1Ω shunts, means you can read the current without doing the math. Doesn't hurt to keep them around in varying wattages. I have 1/4W, 1/2W, 5W, 10W and 100W.
Grab some 20A TO-220 rectifier diodes. They're not expensive and can easily be mounted to a heatsink (with fan if you need100% duty). Submerging them in water isn't the best idea, especially if you're not using DI water. Pure DI water isn't very conductive, but if you have any sort of solutes present in the water then it will become conductive. Will do funky things, especially with any sort of pulsed output.
At first it looked OK, same result, but as I was increasing the current I started to hear a buzzing noise comming from my power supply and the driver, the buzz matched the PWM modulation, I trough my 10A PSU wasn't enough for the high current pulses, so I added a massive 16000uF/50V capacitor in parallel with my PSU, it stopped buzzing but the driver not.
Your 10A PSU should handle the load from a switching current regulator at 4.7A just fine, those switching drivers are quite efficient. Wouldn't expect more than 6A load on your PSU if the driver is bucking (Vin>Vout). What was your input voltage?
As I was adjusting the current, there was a time that the driver just stopped regulating the voltage, showing huge spikes at the output. I turned it off, disconected the PWM signal and turned it on again to have a steady reading of the output current, short time after I turned it on, smoke started to come out of the driver and it stopped working.
What driver are you using?
I already contacted the seller to see if I could get a replacement. I will update this when possible.
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This is the result of the same setup on another driver (this one is limited to 2,4A).
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