Sharing ideas on how to make a more efficent motor using Flyback (MODERATED)

[itsu]

Note, that the maximum supply voltage of this driver chip is only 16V.
That might seem like enough when you are supplying it from 12V but remember that D2 and ZD12 allow the L2 voltage to swing up 18V higher (depending what ZD2 you have installed) and this gives the total of 30V to ground, that can appear on the output of this driver (minus the voltage drop of R3 and D3) so you are pushing the output transistors of this chip and don't be surprised they break.  ...but if this driver is inexpensive, I would not go to the trouble of adding Q4 since it apparently works well alone.
Pretty clever but this way you charge and discharge C2 at the same time.  Q3 should be open and C2 should be discharged, before Q1 opens.

Also, this way you do not have control how long Q3 remains closed. The inductance of L2 determines that for you.
I don't think it was coincidence either.
When I was doing the power calculations for putting a small light bulb in place of R2, I calculated approximately 2W.

Ok  seen this updated bold line, so this is not going to work this way, i have to build in a delay for U2 to fire or use my hall sensor feedback system again.

I will retry that latest option first.

Itsu

[verpies]

...i have to build in a delay for U2 to fire or use my hall sensor feedback system again.

The easiest way to do this is make an additional 555/556 monostable, that will slightly extend the length of the 555/556 astable's output.  See pulse extender.

Now the trick is to use the output of the monostable to provide the "Energize L1" signal and use the output of the astable to provide the "Discharge C2" signal.  This is because the astable's output pulse will end before the monostable's output pulse ends.

[gotoluc]

I'm back and before doing Brad's suggested test I've done a few other tests on the DUT and moved the two CSR on the negative side of the batteries to be able to probe both MOT'S current and voltage at the same time since negative is common ground at the mosfet's by the 2 channel SG.

The first scope shot is E to E core with the 0.6mm air gap and next is no air gap. I see no difference
The flyback diodes are still connected to the 57uf caps with 4.7k load.
I also did a single shot test to measure the voltage by DMM on each cap (no load resistor).
For channel 1 and 2 cap charged to 28v and channel 3 and 4 cap charged to 35v

Channel 1 and 2 is what was probed in the previous MOT scope shots.

The only other test I can think of doing before I make changes to test Brad's suggestion is a reducing the pulse width to where I suggested in the enlarged scope shots with added details.
If you can think of anything else please post your suggestions.

Next post will be the small pulse width.

Lux

ADDED: This may be of importance?  each mot are not identical, their primaries are wound in a different direction when connected in bucking. CH 1 & 2 positive starts on inner winding and CH 3 & 4 positive starts on outer winding. Could that be why the difference at off time?

[gotoluc]

@ verpies

Got some HCF4047BE

Luc

[tinman]

I'm back and before doing Brad's suggested test I've done a few other tests on the DUT and moved the two CSR on the negative side of the batteries to be able to probe both MOT'S current and voltage at the same time since negative is common ground at the mosfet's by the 2 channel SG.

The first scope shot is E to E core with the 0.6mm air gap and next is no air gap. I see no difference
The flyback diodes are still connected to the 57uf caps with 4.7k load.
I also did a single shot test to measure the voltage by DMM on each cap (no load resistor).
For channel 1 and 2 cap charged to 28v and channel 3 and 4 cap charged to 35v

Channel 1 and 2 is what was probed in the previous MOT scope shots.

The only other test I can think of doing before I make changes to test Brad's suggestion is a reducing the pulse width to where I suggested in the enlarged scope shots with added details.
If you can think of anything else please post your suggestions.

Next post will be the small pulse width.

Lux

ADDED: This may be of importance?  each mot are not identical, their primaries are wound in a different direction when connected in bucking. CH 1 & 2 positive starts on inner winding and CH 3 & 4 positive starts on outer winding. Could that be why the difference at off time?

I think ch2 and 4 have to be inverted-would be easier to work out then


brad