Hello every one,
I currently trying a build an thrust test bench for RC motor and i getting trouble with the current mesurement.
I use for that purpose an Hall effect sensor ACS758LCB-050B already package like this
https://www.banggood.com/CJMCU-758-ACS758LCB-050B-PFF-T-Linear-Current-Sensor-Hall-Current-Module-For-Arduino-p-1105517.html?rmmds=search&cur_warehouse=CN
My test setup is :
- 3/4 cells 30 Amps BLDC Motor
- 40 Amps ESC
- 2200 amps/h 30C 11.1V Batterie
- 10x8 prop
Every thing work fine and i got descent thrust
I followed the Henry's bench tutorial and use his code
http://henrysbench.capnfatz.com/henrys-bench/arduino-current-measurements/acs758-arduino-current-sensor-tutorial/
The sensor is put in series between the batterie and ESC.
The problem is that the sensor give me very inconsistent result.
For exemple at 1/3 throttle i got (the forth last read are at 0 throttle)
Raw Value = 541 mV = 2644.184 Amps = 3.605
Raw Value = 509 mV = 2487.781 Amps = -0.305
Raw Value = 603 mV = 2947.214 Amps = 11.180
Raw Value = 510 mV = 2492.669 Amps = -0.183
Raw Value = 587 mV = 2869.013 Amps = 9.225
Raw Value = 502 mV = 2453.568 Amps = -1.161
Raw Value = 567 mV = 2771.261 Amps = 6.782
Raw Value = 503 mV = 2458.456 Amps = -1.039
Raw Value = 524 mV = 2561.095 Amps = 1.527
Raw Value = 537 mV = 2624.633 Amps = 3.116
Raw Value = 508 mV = 2482.894 Amps = -0.428
Raw Value = 604 mV = 2952.102 Amps = 11.303
Raw Value = 510 mV = 2492.669 Amps = -0.183
Raw Value = 542 mV = 2649.071 Amps = 3.727
Raw Value = 506 mV = 2473.118 Amps = -0.672
Raw Value = 585 mV = 2859.238 Amps = 8.981
Raw Value = 502 mV = 2453.568 Amps = -1.161
Raw Value = 542 mV = 2649.071 Amps = 3.727
Raw Value = 509 mV = 2487.781 Amps = -0.305
Raw Value = 510 mV = 2492.669 Amps = -0.183
Raw Value = 508 mV = 2482.894 Amps = -0.428
Raw Value = 510 mV = 2492.669 Amps = -0.183
The motor run like a charm.
It's almost look like to me like AC current. I check with a bad ampmeter (limited to 5Aamp), he gave me around 4amps consistent.
Should I make an average of the reading ? Does it make sense with such variation ?
I tried to plug a basic DC motor with the same batterie (and of course without ESC) and this time the result were consistent and matching my ampmeter.
Raw Value = 517 mV = 2526.882 Amps = 0.672
Raw Value = 517 mV = 2526.882 Amps = 0.672
Raw Value = 516 mV = 2521.994 Amps = 0.550
Raw Value = 517 mV = 2526.882 Amps = 0.672
Raw Value = 515 mV = 2517.106 Amps = 0.428
Raw Value = 515 mV = 2517.106 Amps = 0.428
Raw Value = 515 mV = 2517.106 Amps = 0.428
Raw Value = 516 mV = 2521.994 Amps = 0.550
Raw Value = 511 mV = 2497.556 Amps = -0.061
Raw Value = 510 mV = 2492.669 Amps = -0.183
Have you an idea of the cause of this inconsistency from the sensor?
Thanks for your help and time
Ludovic