- Sat Mar 17, 2012 5:51 am
#141330
I played with some digital implementations of low pass filtering (LPF) and I don't get as smooth a result as the 10 pt moving average. But having said that I'm filtering "noise" which may already be aliased, so I can't stress enough that the current sensor bandwidth (BW) should reduced from it's present 80+ kHz to something more reasonable. I'd say 100 Hz and perhaps even 50 Hz, but I'd collect some data at the 1'st first. Adding a 1uF cap should do just about that. Then some form of digital, post-sampling filtering/averaging can be done if needed (should be less intensive if needed).
I note that the quiet region seem to persist across all the data sets and it orresponds to a region of higher current draw, presumably when the spring is being compressed. So why is the region where (presumably) the spring has been released and the sector gear not engaged and the motor is just "loafing" along so noisy ? Off the top of my head I would have predicted just the opposite.
I note the PWM frequency seems high enough that it doesn't interefere with the desired current measurements. The motor must be filtering out the PWM, just as it's expected it should.
Lastly I wonder if the range of max to min currents, after being smoothed, is large enough and stable enough to be of use in determining where in a gearbox cycle the gun is. I guess I'd wait until seeing the data after the cap has been added to the sensor.
Last edited by Mee_n_Mac on Sat Mar 17, 2012 1:55 pm, edited 1 time in total.