Self running coil?

[gyulasun]

Hi Luc,

Would you insert a 10 kOhm resistor in series with the 3V battery and feed you latest two oscillators above via this 10 kOhm?  Just use any normal small wattage resistor and no problem its tolarance (you can meauser it with a DMM). 
Would be interested in learning the voltage drop across the 10 kOhm, measured with you handhald DVM(s).
Such a huge value resistor should not affect the oscillators operation, due to the microamper current draw only.

(NExt time please try to make DC coupled scope shots too.)

Must go now.
Thanks,  Gyula

[gotoluc]

Hi Luc,

Would you insert a 10 kOhm resistor in series with the 3V battery and feed you latest two oscillators above via this 10 kOhm?  Just use any normal small wattage resistor and no problem its tolarance (you can meauser it with a DMM). 
Would be interested in learning the voltage drop across the 10 kOhm, measured with you handhald DVM(s).
Such a huge value resistor should not affect the oscillators operation, due to the microamper current draw only.

(NExt time please try to make DC coupled scope shots too.)

Must go now.
Thanks,  Gyula

Okay Gyula,


Using the IRFBC20 and running the circuit for 1 minute and 30 seconds the 2% 10K Ohm resistor reached 0.035vdc across it which was measured with my best quality battery operated hand held DMM

Using the IRF640 and running the circuit for 1 minute and 30 seconds the 2% 10K Ohm resistor reached 0.080vdc across it which was measured with my best quality battery operated hand held DMM

Each scope shot (with DC on probe) is below in the order of the above description.

Luc

[mscoffman]

@all

On the above two scope pictures: These two transistor are doing pretty much
what one would expect. The IRFBC20 has got a higher Rds so it doesn't pull
down quite as thoroughly as the IRF640. The higher internal resistance is to
be expected from a higher peak voltage transistor.

What would be great is if you could try a P-channel device. This would invert
the green line on the scope and saturate pulling high, potentially creating a
symmetrical drive waveform. They often build a P-channel device that is a mirror
image of N-channel devices so engineers can build "push-pull" output stages.
This may boost the -24ua reverse current up to -48ua reverse current in a
push-pull two transistor driver circuit. Now, as it is, the transistor pulls down
and the coil floats back up, the drive current is occurring only about 1/2 the
time.

I'll not say whether the spikey part or the saturated part is the most overunity.

:S:MarkSCoffman

[chadj]

@all

On the above two scope : These two  are doing pretty much
what one would expect. The IRFBC20 has got a  Rds so it doesn't pull
down quite as thoroughly as the IRF640. The higher internal resistance is to
be expected from a higher peak voltage transistor.

What would be great is if you could try a P-channel device. This would invert
the green line on the scope and saturate pulling high, potentially creating a
symmetrical drive waveform. They often build a P-channel device that is a  of N-channel devices so engineers can build "push-pull" output stages.
This may boost the -24ua reverse current up to -48ua reverse current in a
push-pull two transistor driver circuit. Now, as it is, the transistor pulls down
and the coil floats back up, the drive current is occurring only about 1/2 the
time.

I'll not say whether the spikey part or the saturated part is the most overunity.

:S:MarkSCoffman

P-Channel MOSFETs are not very common and can't offer the same performance as N-channel. You can get around this by putting an N-channel on the high side of the inductor and connecting the gate to a high-side driver. The driver will hold the gate voltage well above the positive rail for the duration of the cycle.

There are 2 ways to do this:

1. Give the gate its own transformer.
2. Build a circuit that charges a capacitor during the inactive part and shifts the voltage up during the active. There are many available driver IC's that can do this.

Regards,
Jules.

[gotoluc]

P-Channel MOSFETs are not very common and can't offer the same performance as N-channel. You can get around this by putting an N-channel on the high side of the inductor and connecting the gate to a high-side driver. The driver will hold the gate voltage well above the positive rail for the duration of the cycle.

There are 2 ways to do this:

1. Give the gate its own transformer.
2. Build a circuit that charges a capacitor during the inactive part and shifts the voltage up during the active. There are many available driver IC's that can do this.

Regards,
Jules.

Hi Jules,

I have some IRF9640 P channel mosfets and they don't seem to work with the pulse coil. I tried them before and tried them now and I can't make it self pulse.

I don't know what kind of circuit I need since I don't know much about electronics. All I know is, if I had a circuit that could be powered by 3vdc at 10u and capable of producing 7vpp sine wave (square wave may work) at around 10KHz with adjustable frequency, then this Toroid coil should give OU from what I can tell.

If you can provide a circuit that can do this, all credit will be yours!

Thanks for sharing.

Luc