stopping a motor by monitoring the current!

[doggington]

I dont know if this is simple or stupid. Is it possible to run a motor so that it hits a physical stop and then switch off the power having monitored the current. I assume there is a build up when the motor is put under a load! I dont know what this might be called so not much Idea where to look on the forum if its possible.

I am only looking at 6v or 12v motors and picaxe 18m2
any pointers gratefully aknowledged.
thanks

 

[eclectic]

Go to Advanced search, and enter the three words

motor current monit*

Plenty of hits

e

 

[KMoffett]

http://www.romanblack.com/current.htm

Ken

 

[Dippy]

Yes, I believe some leccy car windows had that feature many years before PICAXE was a twinkle in the eye

Search for various methods of current sensing such as op-amps, or the many cheap current sensing chips on the market.
There are some really easy ones to use e.g. search Farnell's inventory.

 

[premelec]

For high side current sense units looks a "diodes" and "touchstone" semiconductor companies - around $1.50 - or just use the resistor in low side... If you set reference voltage in PICAXE to 2.048V you can get a pretty big reading with fairly small low side resistor - however pay attention to ground loops and spike filtering to the PICAXE as we want it to have a long life..

 

[inglewoodpete]

http://www.romanblack.com/current.htm

That is quite a varsatile circuit and easily enhanced.

Roman Black lists a couple of limitations that can easily be overcome. Using a schmitt trigger input on the PICAXE should overcome the problem where the motor is run near its current limit. Replace the LED connected to the transistor's collector with an optoisolator. That way, you need not have any electrical connection between the motor and PICAXE circuits.

Also, the sense resistor may be the current sense resistor on an H-Bridge circuit, allowing a reversible motor configuration. Refer to the L298 Datasheet.