|Aug 18, 2011, 09:27 PM|
ESC RPM Senor
I would like to ask if someone knows of a good way to creating an senor that would connect to one or two wires coming from an ESC? The output from this sensor then would connected to an Arduino and the RPM calculated.
Thank you in advance.
|Aug 27, 2011, 04:46 PM|
Some time ago I tried to build something similar, but had problems with counting PWM impulses instead phase turn on.
Maybe few pictures describe better the nature of the signal:
On the picture is one phase of the ESC. We can see current ramp up, turn on for about 4ms and next ramp down.
On closer look we can see series of impulses. Most probably the circuit described above will count the short PWM impuses instead total phast on.
I tried to filter the impulses, but the signal has wide range of frequency changes, so filter not worked well in all conditions.
More close view of the PWM impulse. Im my ESC it had frequency 7.8kHz.
Finally I builded optical RPM sensor. It works well in all conditions. Actually I use 2 sensors on my quadrocopter. It "looks" on the engines with glued black stickers on the half of circumference. Second half can be with white sticker, or like in my case is reflective metalic body of the engine.
Actually I use the sensors to compare parameters of the drives. For example test run with empty engine and engine with 10x4.5 propeller
Upper graph shows current (red) and voltage (blue), middle graph shows servo signal going to the both ESC. It is scaled in microseconds. Bottom graph shows RPM of the both engines measured with my sensors.
|Aug 28, 2011, 09:10 AM|
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