Quote:
Originally Posted by thingstodo
First - the simulated truck motor.
The PLC5 will have one output wired to a cordless drill. A calculation based on the VFD speed reference (that won't be connected to anything) will drive the drill. Forward and reverse are ignored. The drill will be wired from 2 12V gel cells in series through a DC output on the PLC that only switches at about 100 Hz. The 32 different patterns should give 32 different no-load speeds. The motor is unloaded and may jerk a bit, but it should turn an arbor that has one encoder mounted on it and the encoder will be wired back to the PLC. That's my drive train simulation.
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The first test was done with the drill. The changes in speed are not trivial. The speed for 1 pulse in 32 is like someone hitting the accelerator, then coasting, then hitting the accelerator again ... about once a second.
I tried a few different speeds. At about 4 pulses out of 32, it starts to even out. 8 pulses out of 32 is actually getting to be OK. Then we start running into the uneven spacing between the pulses and get the speed up/slow down cycle until we hit 16 pulses out of 32 or half speed.
I stopped there. There is not much inertia in the drill, so it does not 'average out' the pulses well. The weight of the part that rotates is not very large. The idea was to average the DC and get a fairly consistent rpm.
Next up - try to run the side grinder on 24V DC instead of of 120 VAC. Reduced voltage should reduce the maximum rpm. The current output of 2A maximum for the PLC output should be OK - not a lot of torque required to spin the encoder.