At 06:16 PM 7/12/2005, Gerhard Fiedler wrote: >Hello all, > >I'm looking into moving a lever with a solenoid. It's around 5 Nm torque >and I need to move it 30 degree from a center position in both directions. >It comes back to the center position through its own spring force. My >thought was to use two solenoids and a lever of around 3 cm. That would >give a throw of 17 mm in each direction and a force of 150 N. It seems >that's something a solenoid can do. Needs to be for 12 V. I'm sure this has been suggested before, but why not consider a servo? There are some pretty hefty units rated for industrial duty available. May even be less expensive than the solenoids. >I'm also looking into using starter solenoid coils. They probably only need >a steel rod added to them that they can pull. That may work. > >The other question is how to switch such solenoids. From the Kendrion site >and the solenoid data sheets I found there, I imagine that it may take up >to 60 A to get the force I need. This doesn't seem impossible to switch >with MOSFETs or IGBTs, but I wonder how you get that current to and from >the transistor. A 10 A trace is already large. We don't really need a high >duty cycle, so maybe that works out, temperature-rise-wise. I was just >wondering... are there any special tricks to it? Even connecting the thick >wire to a circuit board seems tricky. High voltage DC stored on a large capacitor. Decays to Vbatt for holding current. I used to fire large solenoids that operated folding seats (Carnival Dunk Tank systems). I charged around 350,000 uF to around 70 Vdc and dumped that into huge solenoids rated for 12V continuous operation. No problems and no failures. FWIW - the solenoid chosen would not work the mechanism reliably below around 36 or so Vdc. I could have used less than 70V but that's what I got out of the transformers I had handy at the time. Used a honking big triac as the switch with a separate bipolar device to disconnect the bridge rectifier from the caps during the firing cycle. All run from a single CD4093 quad schmitt NAND package and a handful of passives. dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 21 years of Engineering Innovation (1984 - 2005) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist