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Author Topic: Self accelerating reed switch magnet spinner.  (Read 289898 times)

MileHigh

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Re: Self accelerating reed switch magnet spinner.
« Reply #135 on: October 10, 2013, 02:46:36 PM »
TK:

On your new clip, you can see the limitations of your small relay-based sense coil.  The waveform is just too flat between magnet passes.  If I was in your shoes I would be tempted to try an alternative sense coil.  I would think of going to Radio Shack and buying one of those fist-sized spools of very light gauge speaker wire.  That should give you a much wider spread in the sense coil output waveform and get rid of the flat spots.  I am guessing you already have something comparable floating around.

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MH, your AC voltage integrator is great... but will it work for a spiky, pulsed DC signal too? But I'm not sure if it is applicable here because any power taken off will be through a diode and put onto a big cap anyway, and there are losses in that process for sure.

The voltage averaging circuit that I described is just another piece of the "convert your cheapo multimeter into a watt meter" idea that I had.  It would do current sensing on the supply battery feed into the drive coil.  It would also do current sensing on the output from the drive coil into a charging battery, i.e.; back to a conventional Bedini-type setup.  There is not really any spiky-ness in those current waveforms and the bandwidth of the op-amp is 3 MHz.  So there should be no bandwidth issues.   Later on I will try to do a simplified schematic and description.

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And your explanation of the torque point is good, for the max RPM case under no load. I'm not sure if the same timing and dwell parameters will apply to the loaded rotor though, since it will stabilize at a slower speed.

Not sure I get you here in the sense that the torque on the rotor as a function of the angle between the energized drive coil and a moving rotor magnet should be independent of load.

MileHigh

synchro1

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Re: Self accelerating reed switch magnet spinner.
« Reply #136 on: October 10, 2013, 03:53:34 PM »
MH:

I agree but,  (always a but) does the frequency not have to increase also or, in TK's set-up, does that happen automatically like in a Bedini motor?  In other words, on mine, I have to change the vr's to get it to accelerate.  This can be done continually until it reaches the max rpm for that configuration.

Perhaps you can explain this:

http://www.youtube.com/watch?v=LfprTzG5SY4

I never was able to figure out why this happened the way it did.  Some folks on Youtube offered their opinions which may, or may not have been correct.

This probably has nothing to do with TK's motor and for that, I am sorry.  (But it might)

Bill

PS  I had mounted the coil on a threaded rod assembly such that I could, with some precision, move the coil's position to the rotor.  I had already found the "sweet spot" in my earlier videos.


Acceleration coupled with increased resistance is relevant. I'm not asking anyone to rewatch any of my excorcist videos. My Bedini circuits behave the same way. What I demonstrated was that once the current tapering produces the maximum acceleration, a loop back to source circuit proves there is no longer any drain on the source battery.


You could try a trifilar wraped power coil to accomplish this. A bifilar, power and trigger coil for the bedini circuit and the third wrap for output. The output would need to pass through a rectifier, then connect directly back to the source battery. Once the reduced resistance produces the maximum acceleration, the loop back circuit creates a zinging effect because power can't run two ways in a wire silmultainiously. A push and pull results. Gadgetmall just wraps the third coil directly over the bifilar.

MileHigh

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Re: Self accelerating reed switch magnet spinner.
« Reply #137 on: October 10, 2013, 07:01:26 PM »
Synchro1:

Quote
What I demonstrated was that once the current tapering produces the maximum acceleration, a loop back to source circuit proves there is no longer any drain on the source battery.

One of the important lessons for anyone to learn when working on the bench is to question their own results when they seem strange or unusual.  That could mean double-checking what you just did or trying to make the same measurement in a completely different way as a means of confirming or denying your first measurement.  Also, some measurements are very difficult to do and it requires a lot of knowledge and skill.  How many clips have you seen where a digital multimeter display is jumping all over the place and the experimenter just decides to "pick" one as the measurement.  That's a huge mistake, and the right thing to do would be to ignore the crazy display jumping all over the place.

I can tell you with 100% certainty that there was still a drain on the source battery when your setup was running at high speed.  If you had a big capacitor in parallel with your battery when you thought you were measuring no current consumption, and then disconnected the battery and let the capacitor take over, then the voltage on the capacitor would drop which would prove that your setup was drawing current.

Quote
You could try a trifilar wraped power coil to accomplish this. A bifilar, power and trigger coil for the bedini circuit and the third wrap for output. The output would need to pass through a rectifier, then connect directly back to the source battery. Once the reduced resistance produces the maximum acceleration, the loop back circuit creates a zinging effect because power can't run two ways in a wire silmultainiously. A push and pull results. Gadgetmall just wraps the third coil directly over the bifilar.

One think to note about bifilar and trifilar setups around a core, and that is that they are all sharing the same available power.  So if you start drawing some power away with one coil, then there is less power available to the other coils.

MileHigh

synchro1

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Re: Self accelerating reed switch magnet spinner.
« Reply #138 on: October 10, 2013, 08:00:48 PM »
Pirate's turning the power down and his rotor's speeding up. I got the same effect from my simple Reed switch version. I went on to report that after the current dropped to zero on the amp meter, the acceleration went hypersonic. I would really love to see your Op Amp circuit run a high speed VCR rotor like Pirate's to see if TK could repeat that effect with scope shots.

TinselKoala

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Re: Self accelerating reed switch magnet spinner.
« Reply #139 on: October 10, 2013, 08:28:59 PM »
@synchro:
Pirate is turning a variable resistor. This doesn't necessarily mean he is "turning the power down" when the rotor speeds up. But even if it does, it could only be something like desaturating the transistor and allowing it to switch better _instead of heating up so much_ on the same or less power input.

We hear a lot of impressive sound from Bill's closeup microphone, but I didn't see any instrumental readings of RPM or frequency of operation in that video. I also don't know the operating voltages that are being sent to the drive coil. A VCR head has good bearings and is well balanced, but installing glue, magnets and tape around the outside will destroy the balance and add aerodynamic drag. There is a lot of aero drag on my very poorly balanced Folger's Instant Coffee jar lid too, but the pivot bearing system is as good as a ball bearing system when it is properly set up. My rotor, which has a relatively low mass, takes a surprisingly long time to run down, unpowered, from its normal 2100 RPM speed: 94 seconds is typical, in fact.
I have no doubt that Bill's rotor is turning faster than the MHOP rotor is. I sure would like to see what his scope shows on that system. I refuse to tear apart my good old VCR, though, and I doubt if I can even find one at a junk store any more. I'll ask around though.

@MH:
I've tried an assortment of different sense coils, short and fat, wide and narrow, high and low impedance, even a loopstick with the core removed. For the coreless coils the relay coil I am using works the best! But for all the coils the width of the magnet passage sinusoid is pretty much the same. I think that it is the magnet spacing that determines the width of the flat spots more than the coil geometry, and I found this to be the case with core-effect  toroidal coils during the Steorn Orbo investigation as well. If I had the ability to make an 8-magnet rotor of the same diameter I think that the flat spots would be gone. Perhaps even a six-magnet rotor using the magnets I used would do it.
But it's really not an issue. Even though the slope of the triggering signal is very flat at what would be a 50 percent duty cycle "start" position, the op-amp is still able to discriminate and trigger stably there. Most of the fluctuation you see in the videos is probably caused not by the flat slope itself but rather because the level of the flat signal is jumping around a bit due to the different magnet strengths and out-of-balance rotor. Still, I can get a 50 percent duty cycle, just not with the very sharp transition as is possible with say 60-40.

MileHigh

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Re: Self accelerating reed switch magnet spinner.
« Reply #140 on: October 11, 2013, 12:01:08 AM »
TK:

Well, if you're happy then I'm happy!  It's amazing the sensitivity of the op-amp inputs.  I just like CONTROL and that setup does indeed give you control.

I just had an interesting idea for next year's Pulse Motor Build-off.  Everybody has to do it based on a VCR helical tape head spindle and the target is the least amount of input power for a given high RPM, say 10,000 RPM.  Or perhaps a hard drive spindle would be even better and they are more readily available.  I was going to say "maximum RPM" but I would hate to see anybody get a shard of metal flying right through their cheapo protective goggles and into their eye.  Also, you are disqualified if you don't purchase some kind of transparent tube of protective plastic to put over the pulse motor.  You could define some standard plastic tube spec that anybody could buy at a Big Box hardware store.  And you have to clearly demonstrate how you make your input power measurement.  You get bonus points if you don't rely on your digital multimeter to heavily.  Can you get creative and use some analog tricks to measure the power input?  Somehow work in a Wheatstone bridge?  Same thing if you have a power output measurement to do.

That might be pushing the envelope too much but you never know.  You can always completely change gears and have an egg dropping competition instead....

MileHigh

MileHigh

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Re: Self accelerating reed switch magnet spinner.
« Reply #141 on: October 11, 2013, 03:35:21 AM »
Well, I am going to try to finish off my "cheapo watt meter" design.  I am sorry to say in Windows 7 I don't think there is a built-in object oriented graphic program for dummies.  I went to the Cnet Downloads page, which used to be my favourite place for safe free software, but it's been corrupted as far as I am concerned and I don't want to struggle with them refusing toolbars at every step and the whole nine yards.  Way back in the 90s there was a great freebie object oriented image editing software program but I forget what it's called.

Okay, here goes.

Here is the project:  Let's assume that you have two fresh 12.6-volt batteries in series powering your pulse motor.  Let's assume that the average power consumption of the motor is seven watts.  So we want to have an op-amp configuration that computes the average of the current pulses coming out of the 25.2 battery voltage source and outputs that average current value as seven volts DC to your cheapo multimeter.  Makes sense?  So the multimeter display is showing seven volts DC which actually means seven watts of average output power.  So effectively you will be using op-amps to construct an analog computer to accomplish this task.

We will power the op-amps with +/- 9 volts using two 9-volt batteries.  That makes for a compact setup.  You could use 12-volt batteries for more headroom but they are large.  The op-amps have to have +9 volts and -9 volts, and you want to have a ground handy (junction of the two batteries) because you will need it.  I wall call that Gnd9V to avoid possible confusion.

Let's look at the logic behind the design.  If the pulse motor is consuming seven watts, and the voltage source is 25.2 volts, then the AVERAGE current flow (not the pulsed current flow) is (7/25.2) = 278 milliamperes.  So the op-amp analog computer just has to sense the current pulses, and then average them to a DC value, and with that average current computation output seven volts DC and that represents seven watts of power consumption by the pulse motor.  (In this design the averaging and the requirement to output seven volts will be combined into one step.)

The design is very basic and I am sure there are better ways to do it - but this should work.

IMPORTANT:  This design is so "dumb" that it will only work for a fixed source voltage.  Of course it can be adapted to work with different fixed voltages, but it's still pretty dumb.

Note also that it will work for measuring the power INPUT to the pulse motor by the source battery, AND it can just as easily work for the power OUTPUT by the pulse motor into the charging battery.

MileHigh

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Re: Self accelerating reed switch magnet spinner.
« Reply #142 on: October 11, 2013, 04:22:06 AM »
Okay, with great trepidation I will try to describe the circuit.  We are going to try using a 0.1 ohm current sense resistor.  But, everything could work just as easily with a one-ohm current sense resistor but certain other values would naturally have to change.

Here is the pipeline:

[pulsing output from source battery] -> [current sense resistor] -> [unity gain voltage follower] -> [inverting amplifier with variable amplification] -> [RC averaging filter] -> [multimeter on DC voltage with inverted probes]

[unity gain voltage follower]
The input for the unity gain voltage follower is on the battery side of the current sensing resistor.
The Gnd9V is connected to the other side of the current sensing resistor.
The only thing this section does is buffer the voltage waveform from the current sensing resistor without loading it.

[inverting amplifier with variable amplification]
The inverting amplifier is where we need to figure out how much amplification we need to generate the seven volts average output.  Let's assume that we have a 1 Kohm input resistor, and a 20 Kohm 10-turn trimpot as the feedback resistor.  So that means the gain for this amplifier can vary between zero and -20.
The inverting amplifier is amplifying the current sensing resistor waveform so that the average voltage of the pulse waveform is negative seven volts.

[RC averaging filter]
The input to the RC averaging filter comes from the output of the inverting amplifier.
The RC averaging filter consists of a 1 Kohm resistor that connects to a 1000 uF capacitor which connects to Gnd9V.
The output of the inverting amplifier connects to the 1 Kohm resistor.
This filter converts the amplified current sensing resistor waveform to a steady negative seven volts DC.

[multimeter on DC voltage with inverted probes]
The red probe of the digital multimeter connects to Gnd9V.  The black probe of the multimeter connects to the junction of the 1 Kohm resistor and the 1000 uF capacitor.
This is your wattage output display -> positive seven volts.

Okay, one more post to crunch some numbers to see if everything will work.

MileHigh

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Re: Self accelerating reed switch magnet spinner.
« Reply #143 on: October 11, 2013, 04:38:49 AM »
Number crunch time.   We are designing this analog computer based on a 25.2-volt voltage source, i.e.; two fresh 12-volt batteries in series.  We will crunch the numbers assuming a seven watt average power output by the batteries into the pulse motor.

The hypothetical average voltage across the 0.1 ohm resistor is 0.278 amps x 0.1 ohms = 0.0278 volts.

That means the op-amp gain to get 7 volts out is (7/.0278) = 252.

I don't like this, the sense voltage is too low for comfort and the amp gain is too high.  Let's change the 0.1 ohm current sensing resistor for a 1-ohm current sensing resistor.

Wih a 1-ohm current sensing resistor note the hypothetical average voltage across this resistor is 0.278 volts and the amplification that we need is now 25.2.   That makes a lot more sense.

So that means that the inverting amplifier can still have a 1 Kohm input resistor.  However, we will change the feedback resistor to a 30 Kohm 10-turn trimpot.   So now our amplification can vary between zero and 30, just what we need.

I am also having second thoughts about the 9-volt batteries.  I am concerned about any possible clipping of the amplified current sense waveform because of limited voltage headroom.  So I would check that on a scope and if there is clipping, then the power for the op-amp would have to be changed to +/- 12 volts.

So in summary:  1-ohm current sensing resistor, 1 Kohm input resistor, 30 Kohm 10-turn feedback variable resistor, 1 Kohm RC filter resistor, 1000 uF RC filter capacitor.

Note that in real life, some of this may need tweaking.  I am really concerned about the amplitude of the current pulses causing clipping at the output of the inverting amplifier.  You could lower the amplification of the inverting amplifier for example by half.  So that means that your desired negative seven volt output representing seven watts would be reduced to negative 3 1/2 volts.  By doing that you give the op-amp twice the headroom for doing the averaging function in concert with the RC filter connected to the op-amp output.  The down side is that you have to add a third op-amp as a 2X inverting amplifier to double the voltage output so that the multimeter reads seven volts again.

MileHigh

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Re: Self accelerating reed switch magnet spinner.
« Reply #144 on: October 11, 2013, 04:52:10 AM »
Now the fun part after you do all that work and all that number crunching.....  How hard or how easy is it to adjust this analog computer to make it do what you want it to do?

The good news is that it's pretty darn easy.   I am going to assume that you can set up a variable current source of some form or other, but even that isn't necessary.

Let's work with the assumption that six watts of average power is supplied by the 25.2-volt source battery for starters.

So the current that you have to put through the current sensing resistor is (6/25.2) = 238 milliamperes.

Therefore, you put your digital multimeter on current measurement and put that in series with the 1-ohm current sensing resistor.  Put some kind of variable voltage source across these two components (throw in a resistor in series with the voltage source if that makes it easier) and adjust the current so that the digital multimeter shows 238 miliamperes.  Then, adjust the 30 Kohm 10-turn trim pot so the output from the analog computer reads six volts.  That's it, the analog computer is now ready to make average power measurements of the pulsing current coming out of your pair of 12.6-volt batteries in series.

Another example...

Now let's work with the assumption that eight watts of average power is supplied by a single 12.6-volt source battery.

So the current that you have to put through the current sensing resistor is (8/12.6) = 635 milliamperes.

Therefore, you put your digital multimeter on current measurement and put that in series with the 1-ohm current sensing resistor.  Put some kind of variable voltage source across these two components (throw in a resistor in series with the voltage source if that makes it easier) and adjust the current so that the digital multimeter shows 635 miliamperes.  Then, adjust the 30 Kohm 10-turn trim pot so the output from the analog computer reads eight volts.  That's it, the analog computer is now ready to make average power measurements of the pulsing current coming out of a single 12.6-volt battery.

MileHigh

MileHigh

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Re: Self accelerating reed switch magnet spinner.
« Reply #145 on: October 11, 2013, 06:08:15 AM »
I have to do a new revision of the design because I am still really bugged by this headroom business, but I want it to still be a dual op-amp design so the whole thing can be done with a single TL082 chip.

For starters, we are going to blow off the unity gain voltage follower.  You don't really need it, it was just there for "show."

Here is the new pipeline:

[pulsing output from source battery] -> [current sense resistor] ->  [inverting amplifier with reduced variable amplification] -> [RC averaging filter] -> [inverting amplifier with fixed 4X amplification] -> [multimeter on DC voltage with non-inverted probes]

So, now you connect the inverting amplifier to the one-ohm current sensing resistor.  However, what we are going to do is lower the gain of the inverting amplifier by a factor of four.  That means if we were going to program the first stage of this analog computer (consisting of the single inverting amplifier and the RC filter connected to the amplifier output) to output negative eight volts representing eight watts, now we are going to program the analog computer to output negative two volts representing eight watts.

This gives the inverting operational amplifier four times the head room to deal with "taller" pulses being sensed by the current sensing resistor.

Now, we have a job for the spare op-amp that remains in the chip.  It's trivial, we just want it to amplify by a factor of four to bring the voltage output back to eight volts.  Note that there is a 1 Kohm resistor that is part of the RC filter.  We don't want this second op-amp to load down the RC filter too much.   Therefore we are going to increase the values of the input and feedback resistors.  Let's say that we use a 50 Kohm input resistor and a 200 Kohm feedback resistor.  The output from this second stage will be eight volts representing eight watts.

So, sorry to throw a monkey wrench into the works, but there you have it.   Revision two is a much better design and has four times the headroom for coping with the current sense pulses.  That also means that you may also get away with using 9-volt batteries again.

TinselKoala

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TinselKoala

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Re: Self accelerating reed switch magnet spinner.
« Reply #147 on: October 11, 2013, 02:21:30 PM »
The schematic currently in use:

Changes:
- eliminated the diode in series with sense coil
- added 2 ea. 22K resistors, one on either side of the Setpoint trimpot to spread out the setting range
- added Secret of DPDT to enable easy reversing coil polarity to run in repulsion mode
- changed mosfet to IRFP450
- changed recirculation diode to 1n4007


MileHigh

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Re: Self accelerating reed switch magnet spinner.
« Reply #148 on: October 11, 2013, 06:50:46 PM »
TK:

Quote
- added 2 ea. 22K resistors, one on either side of the Setpoint trimpot to spread out the setting range

Astounding!  Visualize the voltage dropping like a multi-stage waterfall!

Quote
- added Secret of DPDT to enable easy reversing coil polarity to run in repulsion mode

Hmm.... Think about this one TK.  I looked at your latest clip and I was looking for the switch-on at TDC and I did not see it.

You changed the polarity of the drive coil so that it would push instead of pull when energized.  However, the sense coil is still turning on the drive coil BEFORE TDC (assuming a "zero offset" sense coil angle), when in fact you need to have the sense coil turn on the drive coil at TDC.

I think that you need to invert the sense coil logic also.  Notice that you don't necessarily have to contemplate wiring in yet another switch - just turn the sense coil around by 180 degrees in its mounting.  I am not sure if that will be easy or hard for you to do, I would have to scrutinize your clips again.

MileHigh

TinselKoala

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Re: Self accelerating reed switch magnet spinner.
« Reply #149 on: October 11, 2013, 08:40:29 PM »
Actually, if you think about it a little more, you will see that it is only the Timing control, the physical positioning of the sense coil, that actually relates to the moment of turn-on and turn-off wrt the TDC position.

Yes, reversing the sense coil also, does produce waveform phase relationships like you would like to see... but the timing must still be changed, although not as much, and here's the kicker: the picture from the strobes is the same, once you have found the "sweet spot" of timing and dwell. Here's the scopeshot of the motor running in repulsion mode, with the sense coil also reversed.

What changes is the position that the setpoint pot has to be turned to, in order to get the dwell angle right. The sense coil needs to be moved the width of the "off" time in order to get to the same timing position wrt the drive coil itself, depending on the polarity of the sense coil.

See the following photos. The first two are repulsion mode, sense coil reversed per your suggestion, motor running at best RPM. The scopeshot and the timing position are shown. The second pair, still in repulsion mode, ditto but with the sense coil in my normal polarity.

ETA: The images are "flashless", at a shutter speed of 1/4 or 1/8 second, so the strobes don't show up properly. You can see the strobe indications much better on the video camera; I'll try to show them later on this afternoon if I have a chance.