Has anyone seen Lasersabers new motor runs on 1000uf cap

[conradelektro]

Thanks to advice from Gyula and SeaMonkey, see at

Gyula: http://www.overunity.com/13523/has-anyone-seen-lasersabers-new-motor-runs-on-1000uf-cap/msg364365/#msg364365
SeaMonkey: http://www.overunity.com/13523/has-anyone-seen-lasersabers-new-motor-runs-on-1000uf-cap/msg364301/#msg364301  ,

I could do some more tests with the DadHav circuit.

The new circuit drives the little ring magnet spinner very efficiently (in comparison to all other drive circuits I ever used) but the circuit is very prone to self-oscillations. The value of the capacitor C1 has to be chosen very carefully and also depends on the supply Voltage.

May be the experts have some ideas of how to stop the self-oscillations in a better way (other than with the 10 K resistor in series with the capacitor C1, which seems to be an insufficient way of doing it).

Greetings, Conrad

P.S.: a feedback diode over the coils cuts off nicely the back EMF spikes but slows down the rotation of the ring magnet significantly.

[conradelektro]

An other variation of DadHav's circuit by sMartcreations2010

http://www.youtube.com/watch?v=WTP3f63-u3U

Greetings, Conrad

[forest]

I'm curious...do you have any information or help for replicating this device from lasersaber ?

[SeaMonkey]

Conrad,

Your scope shots of the MOSFET Drain to
Source signals are quite interesting.

It appears that the MOSFET is not turning
off sharply and remains in the partially
conductive linear region for some amount
of time after turn off is desired.   This may
be responsible for its tendency to self
oscillate.

Presently, the MOSFET turn off is accomplished
by discharge of the Gate capacitance through
the 100K resistor connecting Gate to Source.

Reducing the value of this resistance will speed
up turn off and possibly curtail self oscillation.
You may want to try a 10K resistor there and
also a 1K resistor to note differences in circuit
operation with those.

[conradelektro]

Conrad,

Your scope shots of the MOSFET Drain to
Source signals are quite interesting.

It appears that the MOSFET is not turning
off sharply and remains in the partially
conductive linear region for some amount
of time after turn off is desired.   This may
be responsible for its tendency to self
oscillate.

Presently, the MOSFET turn off is accomplished
by discharge of the Gate capacitance through
the 100K resistor connecting Gate to Source.

Reducing the value of this resistance will speed
up turn off and possibly curtail self oscillation.
You may want to try a 10K resistor there and
also a 1K resistor to note differences in circuit
operation with those.

@SeaMonkey: I tried a 10 K resistor between Gate of the MOSFET and Source.

Scope shots are essentially the same.

Self-oscillation has gone away below 11 Volt but seems to be higher above 11 Volt.

I still need the 10 K resistor in series with C1 to make the circuit work.

The problem seems to be the part: base of 2N3906 - 100 K - positive rail - coils - C1 - 10 K resistor - base of 2N3904.

Why is the 10 K resistor in series with C1 necessary? Note, the coils have a rather high impedance (280 Ohm DC resistance).

Greetings, Conrad