Self accelerating reed switch magnet spinner.

[MileHigh]

TK:

Easy fix, just put two ammeters on the high side, one for each voltage.

MileHigh

P.S.:  PW, welcome back!  Please forgive my somewhat amateur "brute force" designs.  I know that you are _The Man_ when it comes to this stuff and I am just a Joe Blow.

[MileHigh]

TK:

About your new clip.  Perhaps there is less power out because your drive coil is coreless and therefore stores much less energy.  That's not necessarily a bad thing if you are comparing input power vs. output power vs. RPM efficiency.  It depends on the measurements of course and the timing timing timing.  It's possible that a drive coil with a core stores "too much energy" and you put in disproportionally more energy per drive pulse than you get compared to the push that you deliver to the rotor.  If your coreless drive coil can make the rotor spin at about the same speed as the same coil with a core, that might be true.  Then the core itself may have a fat hysteresis loop or a skinny hysteresis loop.  It's the area inside the loop that is equivalent to the lost energy.  A certain amount of power gets lost in the sloshing of the magnetic domains in the core.

Anyway, it spins and it outputs real joy buzzer pulses!

MileHigh

P.S.:  Did you ever try putting a super-high voltage cap as the load on a pulse motor just to see what happens when the cap voltage reaches crisis levels?  I figure the diode starts to reverse-conduct after every coil pulse which would make life very harsh and difficult for the diode.

[picowatt]

TK:

Easy fix, just put two ammeters on the high side, one for each voltage.

MileHigh

P.S.:  PW, welcome back!  Please forgive my somewhat amateur "brute force" designs.  I know that you are _The Man_ when it comes to this stuff and I am just a Joe Blow.

MH,

I can't agree with most of your post, particularly the Joe Blow comment, I always enjoy reading your posts.

I thought I'd present some alternate circuit possibilities for hi-side sensing.   

I still do design work so I have to keep up with new IC options, etc (mainly linear and data acquisition).  Some of the new function specific IC's are hard to beat using discrete components, particularly with regard to resistor matching (laser trimmed), thermal stability (low drift) and hi DC accuracy/low offset. 

Also, keep in mind that most manufacturers will send out free samples...

BTW, I still have a full set of National Blue data and linear application books from eons ago, and all the "cookbooks".   

(I did, however, get rid of all my old issues of "Photonics" ...) 

PW

[picowatt]

Little Miss Mosfet.

Oh, that...

[TinselKoala]

TK:

About your new clip.  Perhaps there is less power out because your drive coil is coreless and therefore stores much less energy.  That's not necessarily a bad thing if you are comparing input power vs. output power vs. RPM efficiency.  It depends on the measurements of course and the timing timing timing.  It's possible that a drive coil with a core stores "too much energy" and you put in disproportionally more energy per drive pulse than you get compared to the push that you deliver to the rotor.  If your coreless drive coil can make the rotor spin at about the same speed as the same coil with a core, that might be true.  Then the core itself may have a fat hysteresis loop or a skinny hysteresis loop.  It's the area inside the loop that is equivalent to the lost energy.  A certain amount of power gets lost in the sloshing of the magnetic domains in the core.

Anyway, it spins and it outputs real joy buzzer pulses!

MileHigh

Now that I've got the drive coil mounted the way it is, I no longer can just slide a core into it like I did at first. But it's pretty clear from those early trials that the core, at least the bolt I used, didn't really help much. It did change the waveform, it did warm up quite a bit, it did put asymmetric loads on the rotor, but the RPM and acceleration were about the same. I don't know what would happen at higher power levels with a core, though. I did run the coreless version at 36 v input and there wasn't much gain from that either. Again, I seem to have accidentally (on purpose) hit a sweet spot right out of the gate, as it were.

P.S.:  Did you ever try putting a super-high voltage cap as the load on a pulse motor just to see what happens when the cap voltage reaches crisis levels?  I figure the diode starts to reverse-conduct after every coil pulse which would make life very harsh and difficult for the diode.

No, and I'm hesitant to do it right at the moment as I am running low on spares. After the major rebuild I made an error hooking it back up and blew a mosfet and one half of the original TL082. I'm down to one spare TL082 so I don't want to take any risks at the moment. But once I'm stocked with spares again I will try it and see what happens. If the diode breaks down though I'm pretty sure it will take out the mosfet and the op-amp. (My error actually even fried a trace on the little RS PCB, like blowing a fuse.)
I'm just using a 1n4007 rectifier in there at the moment but I think something like MUR1560 or other beefy ultrafast diode would be better.

I didn't want to put ammeters on the high side because I want eventually to be able to just replace them with current-sensing resistors and scope hookups, and I don't have any differential voltage probes, so I need to keep the probe references at the system ground or negative rail.

Meanwhile... the, er, research continues. Now don't go off half-cocked, you know that I'm not making any claims in the following video, but what I am illustrating has caused others to draw conclusions that might be a bit over the top and premature.

http://www.youtube.com/watch?v=xajlH6wkj_0