Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: lemontree on December 01, 2009, 09:28:32 PM

Title: Solenoid sensing
Post by: lemontree on December 01, 2009, 09:28:32 PM

One early lesson I learned was that if you remove the core from an AC solenoid for a few minutes it will burn out.  That is because its inductance is lower with the core out and too much current flows through the coil.  I wonder if anyone has done any practical work on using a solenoid as a position sensor?
If you apply a small amount of ac ripple to a dc solenoid you should be able to estimate the position of the core by measuring the ac current.  By the time you had done all the electronics for that I doubt it would work out cheaper than a servo however.

Title: Re: Solenoid sensing
Post by: waltr on December 02, 2009, 08:32:01 AM

Yes, I've played with this. There are commercial linear position sensors that use this principle and are called LVDTs. Here are some links:
http://www.rdpe.com/displacement/lvdt/lvdt-principles.htm (http://www.rdpe.com/displacement/lvdt/lvdt-principles.htm)
http://www.macrosensors.com/lvdt_macro_sensors/lvdt_products/index.html (http://www.macrosensors.com/lvdt_macro_sensors/lvdt_products/index.html)

Title: Re: Solenoid sensing
Post by: lemontree on December 03, 2009, 08:56:59 AM

Thanks for that.  Have any interesting robots been made that exclusively use solenoids to move around?  A project for myself would be to evolve a solenoid robot design. If ifs and ands were pots and pans.

Title: Re: Solenoid sensing
Post by: waltr on December 03, 2009, 12:55:24 PM

I think I've seen a robot that used solenoids for movement on Utube.
It was lots of laughs but it worked.