On 7/13/05, Dwayne Reid wrote: > 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. But expensive and huge as dimension. There is a much simpler methode which was first used in the 80' on magnetic tape write-readers (commercial stereos). The problem with the electromagnets is just initialing the current. Then required only a very small current to keep them connected. So, the electromagnet has two coils, one for ignition and another for sustain. A built in switch change the coil after turning on. Simple, without capacitors and using the same supply voltage. best wishes, Vasile -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist