Has anyone seen Lasersabers new motor runs on 1000uf cap

[Farmhand]

This shot below also shows it, but with my return circuit returning the discharge energy to the charging coil, as well as that if the frequency of my motor is correct I get both sinusoidal looking currents and voltage on the coils. mosfet "on time" is between points "B" and "C".

It's important to remember the current wave form in yellow at the top is upside down relative to the other and it's own polarity, i had to do that to display both wave forms at the same time.

The blue trace is the charging coil current and is the right way up, correct polarity displayed.

..

[Wwadvice]

Note to moderator, message removed b/c it took so long to get it approved that it would have been lost way back.

[gyulasun]

Hi Farmhand,

Sorry that I did not follow your posts very thoroughly recently and missed your valuable insight on the direct effect of a diode (snubber) on stopping the current in the coil.  I did not evaluate such snubber diodes in pulse motors, for I either charged capacitors or batteries from the collapsed field's energy when tinkered on such setups in the past. 
Thanks for elaborating on it and for you patience to repeat it.

rgds, Gyula

[conradelektro]

Gyulasun wanted to see a scope shot over the Reed switch while the motor charges the cap (diode in the circuit).

Although my motor is not running by itself from the cap when a diode is put into the circuit, it well charges the cap (only to about 6 Volt, because the rotor can not turn faster than about 200 rpm due to its imbalance) when an air jet is blown over its rim area.

A) To understand what is happening one has to consider what is happening while the motor is running from the 1.3 Volt AAA battery and the rotor is sped up by blowing air over it.

Look at the two scope shots on the top of the attached drawing. While the motor is running from the battery no diode is in the circuit.

B) Then the battery is removed and a diode is put into the circuit. The motor only charges the cap once its speed overcomes the charge already in the cap.

Let's say the cap is charged up to 1 Volt. There is a certain rotor speed which induces an AC current into the coils which has a positive bump of 1 Volt. In order to charge the cap further the rotor speed has to be higher than the one which caused 1 Volt in the cap.

Look at the scope shot on the bottom of the attached drawing.

C) My conclusion:

The charging of the cap when a diode is in the circuit (and the motor runs from the cap) happens when the reed switch is ON and when the rotor speed is higher than would be necessary to cause the momentary Voltage in the cap.


D) The position of the Reed switch relative to a coil and the direction of the turning of the rotor have to be correct if charging should happen. This Reed switch position is also optimal for running the motor as a pulse motor.

E) Might be interesting: with a 1.3 Volt AAA battery the motor consumes about 500 µA and turns with about 150 rpm (rpm measurement with scope, rotor stabilises at a certain speed after a few minutes, depending on supply Voltage). The rotor can not turn faster than about 400 rpm, then it jumps out of its bearings (the top magnet above the axle can not hold the axle straight up any more).

F) I attached a document about the operating principle of a Reed switch which taught me a lot. It shows the areas around the Reed switch are influenced by a magnet (at different magnet approaches).

Greetings, Conrad

[Magluvin]

I would like to give my 2 cents on this point, it is one of the things I showed in the tests I did with my motor, when the coils are snubbed by a diode in parallel the current stops immediately as I showed,

I think its balony. Your 2 cents is worth just that. 2 cents. It can be seen in a circuit, in a sim, and in documents.

From the pdf uploaded below...


"A slowly decaying magnetic flux (the slowest is experienced with a simplediode shunt across the coil)"   


By using the diode across the coil, the magnetic field of the coil is maintained the longest. As you add loads in between or in line with the coil and diode, the magnetic field decreases much faster.

This is about making motors. If by using the diode across the coil the magnetic field is maintained longer than with just the on time of the switch, this is where we can reduce the on time of the switch and still get the same amount of push on the rotor using less input.
And thats the truth.

Mags