Inductance measuring may yet work

A project log for Electromagnetic linear servo

Electromagnetic servo actuator for robots which will combine pneumatic speed and working principle with electronic control.

krzysztofKrzysztof 03/20/2017 at 19:120 Comments

This weekend I've tested "proper" measuring of current, with resistor in series with coil. It's not yet working but atleast I've found that with inserted/retracted core there is difference of 5.35..5.5V (measured on sense resistor) in current min and max for pwm on and off times which should give me enough difference to actually measure position.

Bad news: progress will be slow for some time, my car got crashed and I don't have money for hobbies for some time, so no new pcb version for some time. Also when upper transistor is on, voltage on resistor is positive. When it is off, voltage is negative. measuring current means that there will be negative voltages or over-supply voltage on sensing resistor (physics, bitch!) so I will have to think some more on cheapest and simplest way of measuring this current. For now it would require generating negative voltages for comparators and chips which do this cost more than comparators themselves.

As always: if anyone has any ideas how to measure this beast, I would love to listen you.