TK:

I stand corrected.  Indeed, the flexibility of the moveable sense coil makes the high vs. low "hump order" of the magnet pass moot.  DUH on me.  Plus you have a variable threshold.

Well, everything I stated in my very first posting came true and more!  lol

It's the Swiss Army Knife of pulse motors!!!

MileHigh

This makes the transition less definite and this shows up in noise and even "ainslie oscillations" when the Off interval is short.

Holy crap!  How long will it be before Rose claims credit for this device?  There may be a paper in the works as we speak.

Bill

PS  Great work TK and I really enjoy seeing the blending of MH's original idea and your building skills and modifications.

TK:

If you need a vcr hub, I can ship you one.  (free)  (as in, no cost)  A buddy gave me 5 of them and I cleaned out my lab a while back and got rid of most of them but, I can find one for you if you would like.  Very good bearings and a stable platform.  I have used hard drives also but, the vcr head is more heavy duty, so to speak.  Very easy to take out the internal wiring and put back together.

Bill

Tyson:

Thanks a lot and I am well on the way with the Dia program and will have the schematic posted tomorrow.  The program is quite intuitive and I just plunged into it and started making progress right away.  It's not going to be a perfectly clean schematic but it will be perfectly readable.  A simple and good object-based drawing program with various symbol libraries is indispensable.  The fact that it's free is fantastic.

MileHigh

Here we go, the actual circuit!!!  - Thanks Tyson!

Stable running at 1285 RPM, total input power around 1.3 Watts using inline DMM for current. This is for comparison with what we get using the MH comparator-computerator once I get it built.

I assume that a lot of pulse motor builders are watching this thread and are learning as we go along.  So much the better and I hope that some people are being inspired.

I wanted to discuss how to get more speed in somewhat abstract terms.  To get speed you need a low friction rotor and good timing with full control, and power.  The low friction rotor is a mechanical issue that each builder deals with on their own terms within their own budget and available materials, etc.  Good timing with full control has been taken care of with the MileHigh op-amp circuit.

So what about power?  Let's assume that we have a typical 12-volt battery source and a standard drive coil with a core.  What can we do to get stronger magnetic field pulses produced by the coil?  Let's assume that the physical size of the coil remains about the same.  In other words we need to think of some way to push more power through the coil to create stronger magnetic field pulses without changing the physical dimensions of the coil.

Note also that the average pulse motor builder does not know if they have saturated the core in their drive coil.  It's an issue that's never even discussed as far as I am aware.  That is something that ultimately may come into play and there are ways of checking for that but we are just going to put that issue aside for the moment.  Let's just focus on this issue of getting more bang out of the coil for a faster spinning rotor.

Notice again, that this is almost uncharted territory.  Builders make a drive coil with or without a core (I believe most use a core) and then it's more or less a given - they work within it's constraints and worry about other things.

Okay, that was the setup, so let me start a fresh posting to look at this issue - How can you supercharge your drive coil?

MileHigh

So now that we know that a 50-turn drive coil for your pulse motor is just as good if not better than a 100-turn drive coil, how do we take advantage of that?

I am assuming this part is something that will come naturally to most builders, it's very easy, especially if you are using the op-amp timing circuit.

So you take your 100-turn drive coil and you split it into two 50-turn coils.  You use TWO MOSFETS, and there is nothing stopping you at all from using TWO separate batteries sharing a common ground if you are worried about the increased load on a single battery.  Or perhaps you have a big beefy bench power supply and supplying the increased current is not an issue.  (Note you don't necessarily need to use two MOSFETs either.  This is where you start looking at spec sheets.  It all depends on how much total current you are dealing with. In the real world you rarely see "over design" because that increases costs.  However, having separate MOSFETs is "sexier" and more fun!)

There is a very decent chance that the active pull-up and pull down of the op-amp output will be able to drive the two gate capacitances of the two MOSFETs.  This is where you check with your scope.  If yo have to, nothing is stopping you from adding a MOSFET driver chip if you want.  My feeling is you won't need one but I am not sure.  I looked at the schematic for the TL082 and I think it's output impedance for sourcing or sinking current is 50 ohms.

So there is your supercharged drive coil:  You double the magnetic field strength of the drive coil if you split the coil into two halves and you decrease the energizing time constant by one half.  Nothing is stopping you from splitting it into three or even four if you want to.

Of course it goes without saying that when you do this you pay a price for this:  You double the current consumption and you double the power consumption of the drive coil also.

Finally, you have a "real" bifilar or trifilar or quadfilar application for a coil that really does something - it supercharges your drive coil.  It might require more batteries and more MOSFETs, but that should be cool and a fun thing to build.

A coil like this might be so powerful that it will saturate your core.  That has the potential to create "current runaway" so you should monitor your drive coil to make sure it does not get too hot.

You want to dump the current pulses into a charging battery?  No problem at all, just give each coil its own separate diode and it will work perfectly.

You can wind a bifilar yourself, or just buy a spool of speaker wire.  Or, you can fill up the front half of the spool with one integral coil and the back half of the spool with another integral coil - it won't make a damn difference in the world - the only thing that counts is ampere-turns.

MileHigh