| Electronics > Beginners |
| Constant current load Help needed |
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| LukeB:
Hello helpers. I have been having problems with a simple constant current load I have been trying to make based of a video I saw on greatscott's youtube channel. I have made a version of the schematic for myself which is linked as pdf. It for some reason will not lower the current below 1.8 amps. Does anyone know why this would be. BTW I now realise that the approach scott used was rather terrible. The mosfet ends up in that highly resistive part of its curve and heats up a lot. I will now find a better way of making a constant current load but still want to figure out what went wrong with this design. Thanks |
| LukeB:
VCC is 12v by the way and the battery being tested is a 12ish volt car battery (and others in the future). |
| xavier60:
You will need to measure some voltages to find the problem. If the circuit is oscillating, nothing will make sense. Do you have an oscilloscope? Or try some various value resistors in series with the Gate, close to the Gate. It might also help to slow down the op-amp with a small capacitor between the output and inverting input. A resistor will need to be put in the feedback path. The MOSFET's dissipation power will always simply be D-S voltage multiplied by current. |
| LukeB:
Yeah I do have an oscilloscope. Without the capacitors it will oscillate but once they are in there there are no oscillating voltages that I can find. |
| LukeB:
Why does there need to be a resistor in the feedback path? |
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