Here is a mosfet circuit using a H11D1 opto-isolator and 4422 driver that I am testing out now. The IRFP460 mosfet is rated at 20A and 500V and it has .3 ohms resistance.
So far this circuit works great switching motor coils.
Put 5 of these mosfets in a paralell cluster and it would work well switch-shorting coils at peaks since then the resistance would be really low...
Also put another cluster of 5 in paralell and then hook together the clusters of 5's gates and source leads so that switching then occurs between the "leftover" drain leads; ("bidirectional"mosfet hookup) and now it will switch AC and this is a very good coil-shorting circuit.

Quote from: konehead on August 11, 2011, 03:05:10 AM
Here is a mosfet circuit using a H11D1 opto-isolator and 4422 driver that I am testing out now. The IRFP460 mosfet is rated at 20A and 500V and it has .3 ohms resistance.
So far this circuit works great switching motor coils.
Put 5 of these mosfets in a paralell cluster and it would work well switch-shorting coils at peaks since then the resistance would be really low...
Also put another cluster of 5 in paralell and then hook together the clusters of 5's gates and source leads so that switching then occurs between the "leftover" drain leads; ("bidirectional"mosfet hookup) and now it will switch AC and this is a very good coil-shorting circuit.

Could you draw in another mosfet in parallel so i know how to connect them in parallel?
I want to try this circuit also... thanks.

regards, scratchrobot

Quote from: supersam on August 10, 2011, 10:28:10 PM
i think your numbers are at least interesting,and like i said, this coil has got to be a pain in the ass to build.  you said that you wound it a little haphazardly, do you think it would have better performance if it was wound machine like?  interesting!

Well having a machine wind them would at least allow to maximize the number of turns in a specific coil wind area.  Winding by hand, especially on such a small scale as the sewing machine bobbin, makes poor use of that space.  Much space is wasted as the strands cross over each other and previous wraps creating many gaps.  So I ended up with much wire that I could not get on the coil when compared to the mono and bifilar coils.  Those other two have nearly identical amounts of wire on them.

I'd like to find a way to compare these different coils "apples to apples".  But it is near impossible to get similar number of wraps in the same area with the same size wire in order to achieve the comparable impedance's with the same resistance.

The method I use to match the impedance (inserting ferrite to different locations in each coil until they read the same on a meter) has the draw back that when testing by placing the coils at the same distance from the spinning rotor magnets, the ferrite coils are at different distances from those rotor magnets.

If I insert the ferrite cores to the same location with respect to the coil face and therefore the rotor magnets, then the initial induction values will not be the same.  But is there still a way that V p2p readings of this type of setup can be compared?

M.

Quote from: scratchrobot on August 11, 2011, 08:32:00 AM
Could you draw in another mosfet in parallel so i know how to connect them in parallel?
I want to try this circuit also... thanks.

regards, scratchrobot

Gates to Gates, Sources to Sources, Drains to Drains simple )

Quote from: xenomorphlabs on August 11, 2011, 09:21:00 AM
Gates to Gates, Sources to Sources, Drains to Drains simple )

thanks.