Anything new?

simple question related to shorting coils : how can I synchronize square wave generator with sinewave so square wave will start when sinewave start (at zero volts) ?

hi Forest and everyone
here is very good circuit that can control a bank of mosfets to do coil shorting at peaks.
It was made up by Ron P from Canada and he built one and it works great, so did I, and another person named Justin in USA also built this circuit so its been tested out and works fine.
the first pot you adjust to find exactly where in the sinewave you want to trigger  the switching (mosfets)..so you can have the swtiching turn ON right in middle at peaks, or little before or after ore even down at the zero line area if you want.
the 2nd pot adjusts the "capture width" that you want to have - narrow, or wide...
the 3rd pot chops the capture-period selected up into a frequency of your choosing...
for coil-shorting at peaks, you want to use ultra-low resistance switching, or else too nuch resistance will snuff-out the HV and HF ringing that happens with coil shorting (the ringing created when switch OPENS after shorting coils,  is why the caps will fill so fast and so high)
Its best to have a very narrow pulse width to the coil short, and at peak, in order to make it
non-reflective (no extra draw)
Good idea Ismael gave me is to use many mosfets in paralell - like 5 or 10 this will give you very very low resistance...use a driver chip that can supplly lots of amps so that the paralelled mosfets will all swtich ON-OFF same time. I like the 4421 or the 4422....whihc one you chosse will make the swtihcing Non-SWoff or Noff-SWon...you need this sort of thing for a "two stage" output circuit...(see below)
Also for coil-shorting you should have BIDIRECTIONAL mosfets - that is, two mosfets connected at gate and source leads (or two banks of paralelled mosfets) so the mosfets will switch AC...the switching now occurs between the "leftover DRAIN" leads of the mosfets.
I like to put 10K "pull down" resistors across the gate and source leads of each mosfet, and also one across the whole cluster too, if you are going to paralell mosfets for the low ressitance reason...this way if somethign blows up, the driver chip will fry, but the mosfets will be OK....
If coil shorting, DO NOT hit a load directly with the power from the coil-shorted created ringing HV and HF...instead to rectify it, and simply fill DC caps...this  is your first objective - as fast and as high as you possibly can, ...... then after filling the caps, dump caps to the load  you choose.
at same time during the cap-discharge-to-load  the caps must be  DISCONNECTED from the coils being shorted, when caps do hit the load, this is called a two-stage output circuit....other metthod of outputting the caps is to dump the "collector" caps into a 2nd bank of caps, then  2nd bank of caps hits load - this way the collector caps isolate the coils being shorted from the resistive load (AKA "bucket brigade" method)
here is Ron's "dual 4047" peak sensing/capture/chopping circuit:
 
 
 

Hi forest
 
J2 and J3 are the Junction "out"s I guess is what the J stands for...there are two of them in case you choose to skip the chopping feature that you can do with the pot 3
These hook up to the gates of the mosfet banks, its the signal that finally triggers the mosfet banks.
you need to have a trnasformer with AC signal that matches up with what you want to short - lets say you want to short the run-cap phase of a rotovertor AC motor - so good idea for that is put the HV side of a MOT (Microwave Oven Transformer) across the run cap phase, and use the LV side of the MOT to control/signal this circuit.
If you have some sort of generator working that you want to short the phases of the coils at peaks, then put across a coil or phase, some sort of small transformer, or even a small aircore coil, to create the AC siden wave that triggers this circuit...just check with scope that the "signal" wave form look similar to what you are actually going to be shorting.

Hi Forest
 
Here is schematic showing two mosfets hooked up bidirectionally, also it is a coil-shorting circuit too. Note the 10K pull-down resistors too...which make it so the driver chip will the sacrifical component, not the mosfets, if some wires get crossed or something.
This circuit has its timing of when the mosfets turn ON-OFF controlled by hall effects, which would work with a generator-rotor spinning around  wtih some small trigger-magnets on rim of  rotor, in order to trip the hall effects....so to find peak period, all you have to do is adjust the position of the hall effects in relation to the spinnign trigger magnets... you can  mount the halls on a adjsutable swivel- plate that can be locked in place once you find the timign you want...
the small coil off to the left is jsut a way to replace the 9V battery, that supplies the small DC power for the switching (driver, halls and mosfets)  via being induced by the rotor-magnets, once the generator rotor gets going around....
 

hi Forest
Use high voltage rated caps, and I dont like to make too much voltage in first place, from the gernator coils before they short at peaks to keep voltages down...figure about X20 voltage you get in cap form the short, over some time, and "instantly" you get X3 voltage...you will need to discharge cap periodically too,    The UF value of cap you need to find considering what load you have, and how fast and how high of voltage you will get and need - a high UF value will fill slower, low UF  will fill faster...you will get more power from high UF, lower power from low UF so there is a balance you need to find when choosing the DC cap that collects the ringing created from the short.

hi Mags
those homemade caps are only 1.9someting NANO FARAD so they are way too small to store any power worth anything when they discharge to a load.
the caps that collect the ringing from the peak-short should be polarized, DC type also.
I like to use these HV caps - they are cheap too whihc is nice thing - I have ordered around 50 of them...you can paralell or series them:
http://www.allelectronics.com/make-a-store/item/PPC-273/PHOTO-FLASH-CAPACITOR-270UF-330WV/1.html
 
flash caps are good ones to use, since they are made to store and discharge power very quick -like what you want to do with caps in coil-shorting circuit,,.. common electrolyctics  are made to STORE power for fairly long periods in most uses for them, so these dont fill up as fast and easily since they arent really designed for that.
here are some HV diodes too:
http://www.allelectronics.com/make-a-store/item/D660/RECTIFIER-DIODE-6-AMP/600-PIV/1.html
 
 
 

What? I am afraid I don't understand the schematic. When the driver chip's output goes HI, both mosfets will turn on, shorting both coil leads to "source". When the driver chip's output goes low, the mosfets are disconnected from everything except the "ac capacitor" , the fwb and the reservoir cap to the right.  This might allow that cap to charge with DC from current induced in the coils by the rotor motion, but where does any drive pulse to the rotor come from?
Please explain the schematic and what you are trying to do with it.