Self accelerating reed switch magnet spinner.

[MileHigh]

I can't resist because my previous posting suggested a neat experiment that is doable.

Supposing that you build the op-amp based analog computer to measure the average pulse power going to your pulse motor.  It's absolute accuracy might be +/-5% for the sake of argument.  However, it's _relative_ accuracy will be deadly accurate.

So here is the experiment:

You wrap your drive coil in a layer or two of thermal insulation with an impervious outer layer with something like saran wrap.  You have to do this because you assume that the spinning rotor is going to create air currents and you want to mitigate the effects of the air currents on your temperature measurements on your drive coil.  Also, when the drive coil is wrapped up like that you trap the heat production and it will be easier to detect any differences in thermal effects.

So with your infrared temperature measurement gun you make three measurements in three spots on the drive coil then you wrap it back up.  You lock the rotor on your pulse motor very firmly so that it cannot move at all.  Then you pulse the drive coil with a 555 timer circuit as the timing reference and you make spot checks on the drive coil temperature every half hour or hour, to be determined by the experimenter.  The 555 timer circuit is set up to create pulse timing that is a very close approximation of the actual timing of the running motor.  You briefly peel back the insulating layer to make your temperature measurements.  The whole time you are doing this you are monitoring the live power consumption of the drive coil with your analog computer circuit.   Let's say for the sake of argument the power consumption is 1.5 watts.  Let's say after five hours you are satisfied with the temperature data that you have recorded.

Then, you remove the insulation, and you wait until the next day.  It's really really important that you wait a full day for the coil to cool down.  In theory, the coil "never" cools down all the way, so you play it safe and wait a full day.

The next day you repeat the experiment but this time with the rotor spinning.  With your MileHigh pulse motor timing circuit and your real-time average power monitoring with the analog computer you can quickly and easily set the average power consumption of the running motor to 1.5 watts.

What you should see is that the rate of temperature increase of the drive coil when the rotor is spinning is slower as compared to when the rotor is fixed.  This proves that power is being exported to the outside world by the drive coil and it is not heating the drive coil, it is spinning the rotor instead.

This is an experiment that proves to you that the conservation of energy applies to a pulsing drive coil in a pulse motor.  There are no magical curlicues of some imaginary vortex whatever entering via the side of the coil via a Bloch wall that doesn't even exist, which is what Johnny Badonkadunk wants you to believe.

Granted, this experiment doesn't really do anything except prove to you that some of the electrical power that you pump into the coil does not heat up the coil.  Some of it flows into the outside world and makes the rotor spin.

MileHigh

[MileHigh]

TK:

I will just comment on the analog computer circuit and some "weaknesses" in it, although that is too strong a term.  These are just some points for consideration.  They are not critical, just perhaps minor nuisances.

In a standard inverting amplifier configuration for an op-amp like we see twice in the circuit, the negative differential input pin is effectively a virtual ground because of the negative feedback servo amplifier.

When you look at the current sense input, you have a 1-ohm resistor effectively in parallel with a 2Kohm resistor.  So that's a 2000:1 ratio and you can pretty much ignore it.   The op-amp will not "disturb" the current measurement in any significant way at all.

In the RC filter stage though it's a different story.  You have a resistor divider network formed between the 1Kohm resistor and the 50Kohm resistor.   That's a 50:1 ratio and that means that the second-stage inverting amplifier is going to pull down the capacitor voltage a bit.  That's less than ideal, but it has been a long time that I have worked with op-amps and I was "playing it safe" in a manner of speaking.  I was worried about making the second-stage feedback resistor too high in value.

Here is a possible tweak:  Let's assume that you want to keep the RC time constant at one second.  Instead of 1Kohm + 1000 uF, you could change that to 500-ohms and 2000 uF.   The 500-ohm resistor is not an issue for the first op-amp at all.  Since it is a negative-feedback servo-amplifier the output impedance of the first amplifier is "zero" within certain constraints and you never go outside of those constraints.

Similarly, you might be able to change the 50Kohm and 200Kohm programming resistors for the second op-amp for 100Kohm and 400Kohm.   The assumption is that this is okay for the op-amp and it will work just fine.  Like I said I am not an op-amp guru so let's assume that this is true.  Obviously there is a limit for how high you can make the value of the feedback resistor and still have rock-solid signal integrity but I don't think a 400Kohm feedback resistor is anywhere near that limit.

If you try those changes, then the resistor divider that's associated with the RC filter is 500-ohms and 100Kohms.  So now we have a 200:1 ratio, which is a lot better than 50:1.  So with this modified configuration the second op-amp will be much less of a "drain" on the RC filter and "disturb" it much less.

The second issue is that there is no zero offset compensation on the non-inverting differential input pin for either op-amp.  If you look at the National Semiconductor applications guide you will note that most of the circuits do some kind of zero offset compensation.  I am making a reasonable assumption that any offset will be in the range of a few millivolts and can be ignored without it mucking the measurements up at all.  In other words, with no current going though the current sense resistor, and with the analog computer calibrated for your selected voltage source for your pulse motor, you might see a few millivolts at the output instead of zero.   Big deal, it's to make measurements on a pulse motor and the power draw for a pulse motor is never near zero.  So I am pretty confident that you can completely ignore this.

Note this is not meant to be a high-precision power measurement device.  It's intended to allow you to see the live power consumption of your pulse motor input or output as you make changes to various parameters.  For example, even moving the drive coil closer or further away from the rotor will likely show up as a power consumption change.  And like I said before, the delta power measurement should be deadly accurate.

MileHigh

[TinselKoala]

The MHOP performs useful work. It's circulating air, driving the EP5043 propeller.

[MileHigh]

Could be the start of a new fashion trend and therapeutic system!

[synchro1]

Not to be outdone, a 5000 year old rotor from the tomb of Hemaka at Saqqara: