Has anyone seen Lasersabers new motor runs on 1000uf cap

[conradelektro]

What current consumption is involved from the supply when the reed is used?

The current consumption with the Reed switch is about double in comparison with the MOSFET (as a switch).

2 mA at 2 Volt with the Reed switch and 1 mA at 2 Volt with the MOSFET. The Reed switch circuit consumes about 500 µA at 1 Volt (MOSFET does not work at 1 V).

Greetings, Conrad

[gyulasun]

Well, then the Rds ON resistance seems to be twice as much than the ON resistance of the reed, this is an addition to the losses.

Gyula

[conradelektro]

Tests with two Reed switches showed no visible improvement over one Reed switch!

It seems that charging of an external cap with a "low Voltage and low Amperage pulse motor with high impedance coils" works best with one Reed switch (instead of a transistor as a switch). The introduction of a second Reed switch did not visibly improve cap charging.

The second Reed switch increased the drag on the rotor and made operation at 1 V impossible. The motor runs nicely with one Reed switch at 1 Volt supply Voltage.

Is it possible to feed the charge from the external cap back into the circuit in order to lower its power consumption? Many tried and did not succeed, therefore I leave it at that for the moment.

I have the impression that charging the external cap increases the power draw of the motor by about 10%, which is difficult to measure consistently. Also the rotor seems to slow down a bit when charging the external cap. The charging of the 100 µF cap happens rather slowly, very much slower than the 1000 µF cap drains when running the motor.

Greetings, Conrad

P.S.: I did some more tests. The three circuits depicted in the attached diagram seem to cause the same external cap charging and seem to have about the same power draw:

2 V supply Voltage, 0.5 mA average power draw, 4.7 µF (400 V) charged to at least 12 Volt (takes a few minutes, 1N5711 diode used)

6 V supply Voltage, 1.6 mA average power draw, 4.7 µF (400 V) charged to at least 50 Volt (takes a few minutes, UF4007 diode used)

It is hard to see whether power draw increases and rotor speed decreases a bit during external cap charging. Beyond my measuring capabilities. Let's say external cap charging does not change significantly the behaviour of the motor.

[TinselKoala]

You have a rotor that is symmetrical, so it is fairly easy to calculate the rotational moment of inertia, based on the geometry and the masses of the individual parts. Once you know your MoI, then you can know the energy in Joules stored in the rotor's spinning simply by knowing how fast it is spinning.
So then the "cost" of charging the capacitor, which slows the rotor down, is given simply by subtraction. Since you know the amount of energy in a capacitor by knowing its charge voltage and its capacitance in Farads, the efficiency of the charge transfer of energy from rotor to capacitor, and back again, can be calculated with some precision.... as long as you can measure your rotor speed precisely and in real-time. In fact the major source of error in this process is the capacitor value, usually.

Do you have any way of measuring your rotor RPM, like an oscilloscope, or maybe an Arduino and a photodetector or Hall sensor?

[Magluvin]

Tests with two Reed switches showed no visible improvement over one Reed switch!

I went through this a while back. I used 2 led's one for each reed and a battery with current limiting resistor each for the leds. This will allow you to see the timing of the reeds to get them as close as possible.

In Ossies circuit, even if the reeds are not 'perfectly' switched on and off(off being the most important) it should work well at getting current back to the drive battery. For example, if one reed switches off before the other, the coils collapsing can still flow through a diode and the reed that is not off yet to keep the inductor going till the reed finally opens. Is a unique circuit.  I would try my reed/leds timing method before giving up on the 2 reed setup. Or use a 2 ch scope to see the timing. The leds work well and you will be able to really see at very slow hand operated speed of the rotor.

Mags