sensorless motor stall detector?

Home / the12volt's Install Bay / Car Security and Convenience / sensorless motor stall detector? (

Topic Closed)

Welcome Guest :)

Members

Search

Register

Login

< Prev Topic Next Topic >

rob_fed

Member - Posts: 15

Joined: June 10, 2004

Location: United States

Posted: September 09, 2008 at 6:13 PM / IP Logged

I have been experimenting with a few small gear head motors, I have managed to motorize a hinge on small lid that covers a compartment centered on my dash. I used two micro switches to detect whether the lid is full open or full closed. I was wondering if someone had a circuit that would interrupt the power to a motor when it stalls out due to a physical load. From memory, a power window module that hooks up to an alarm seems to perform the same function. But if there is a quick and simple way to detect when a motor is stopped when power is still applied, I could then build off of this concept.

Thanks - rob

Back to Top

KPierson

Platinum - Posts: 3,527

This member consistently provides reliable information

Joined: April 14, 2005

Location: Ohio, United States

Posted: September 09, 2008 at 8:05 PM / IP Logged

One way to go about it is with a very low resistance shunt resistor between ground and the motor. Something like a 0.005 - 0.025 ohm resistor would work. You can then monitor the voltage at the junction between the resistor and the motor. Due to Ohm's law, if the current of the circuit goes up while the resistance stays the same, voltage must change. You can set a voltage threshold with a comparator circuit (or an A/D converter) to kill power after the motor has reached the preset current.

You may run in to issues at start up, so you may need to set two different thresholds - a start up and a running value. That way when the motor first starts and the current spikes the circuit won't shut the output off (but if the motor is already at the end of travel then it won't keep pushing because it will be monitoring the higher preset).

I've never actually built a circuit like this but I've always wanted to. You can actually find formulas on the net to create the shunt resistor with a copper trace on a circuit board.

Kevin Pierson

Back to Top

noisy crow

Member - Posts: 13

Joined: April 06, 2008

Location: Ontario, Canada

Posted: September 10, 2008 at 5:35 PM / IP Logged

Another way.... stick a timer on it. In fact, you can probably get rid of the limit switches if you use a timer. Just run the motor for 5 seconds (or whatever works) and then have turn it off. With a two or three relays

If you search the site for "relay timer" there a bunch of good ideas... like this one: https://www.the12volt.com/installbay/forum_posts.asp~TID~105514~PN~1

Back to Top

rob_fed

Member - Posts: 15

Joined: June 10, 2004

Location: United States

Posted: September 15, 2008 at 1:01 AM / IP Logged

Thanks for the replies. Both the comparator and timer ideas are great. But I was still looking for something that was slight less complicated. I think I have a circuit that is working, but not fully tested. It consists of a latching relay in series with motor. The motor stalling causes the latching relay to latch which opens up the power to the motor. I will need to test further and will post a diagram appropriately.

Back to Top

Sorry, you can NOT post a reply.
This topic is closed.

Printable version

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot delete your posts in this forum
You cannot edit your posts in this forum
You cannot create polls in this forum
You cannot vote in polls in this forum

Search the12volt.com

Follow the12volt.com

Disclaimer: *All information on this site ( the12volt.com ) is provided "as is" without any warranty of any kind, either expressed or implied, including but not limited to fitness for a particular use. Any user assumes the entire risk as to the accuracy and use of this information. Please verify all wire colors and diagrams before applying any information.

sensorless motor stall detector?

Sorry, you can NOT post a reply.This topic is closed.

Sorry, you can NOT post a reply.
This topic is closed.