Rosemary Ainslie circuit demonstration on Saturday March 12th 2011

Rosemary Ainslie · June 19, 2011, 11:07:54 AM

Quote from: poynt99 on June 19, 2011, 11:00:59 AM
If you are referring to the attached diagram, then "D1" replaces Q1, not Q2 as you have stated above.

As I have explained some time back, Q2 (M4 in the attached diagram) is the only active device in this circuit (or paralleled Q2-Q5), and it is this device that causes the oscillation.

I missed that. Thanks Poynty. What then is the function of that diode?

Regards,
Rosemary

Added. What I'm actually asking is does it work WITHOUT the diode?

poynt99 · June 19, 2011, 11:17:16 AM

Quote from: Rosemary Ainslie on June 19, 2011, 11:07:54 AM
I missed that. Thanks Poynty. What then is the function of that diode?

Regards,
Rosemary

Added. What I'm actually asking is does it work WITHOUT the diode?

Quote from: poynt99 on June 19, 2011, 11:00:59 AM
D1, as I explained, is the internal body diode of Q1, and causes the asymmetry seen in the wave forms. The circuit oscillates just as well without D1 (Q1), but then the asymmetry vanishes.

D1 was added to the circuit to emulate and illustrate what function Q1 is actually serving. It is not a perfect replacement because of other parasitic components in the MOSFET, but that body diode is the fundamental component causing the asymmetry in the circuit. Just as well, the actual Q1 could be left in the circuit.

.99

Rosemary Ainslie · June 19, 2011, 11:22:41 AM

Quote from: poynt99 on June 19, 2011, 11:00:59 AM

As I have explained some time back, Q2 (M4 in the attached diagram) is the only active device in this circuit (or paralleled Q2-Q5), and it is this device that causes the oscillation.

.99

This is WRONG by the way. Q2 is responsible for the oscillation. I know this. But for the total control of the required heat outputs we need Q1. I'm not sure how else to increase the heat to get the system to work. It needs the oscillating cycle but the heat output is exponentially increased subject to some small required output from the battery during that short 18% ON time. It only needs to be a little under a quarter of a watt to get the element to that 240 degrees centigrade.

Rosemary Ainslie · June 19, 2011, 11:32:41 AM

Quote from: poynt99 on June 19, 2011, 11:17:16 AM
D1 was added to the circuit to emulate and illustrate what function Q1 is actually serving. It is not a perfect replacement because of other parasitic components in the MOSFET, but that body diode is the fundamental component causing the asymmetry in the circuit. Just as well, the actual Q1 could be left in the circuit.

.99

Do you KNOW this? Here's what I'm asking. What happens to the oscillation when there's NO diode and NO Q1? Have you done this?

Thanks for the answer btw
regards,
Rosie

poynt99 · June 19, 2011, 11:39:38 AM

Quote from: Rosemary Ainslie on June 19, 2011, 11:32:41 AM
Do you KNOW this? Here's what I'm asking. What happens to the oscillation when there's NO diode and NO Q1? Have you done this?

Thanks for the answer btw
regards,
Rosie

Yes, I have done this in the simulation, a long time ago when I reduced the circuit down to just Q2. I may not have posted a scope shot, but I believe the oscillation frequency increased slightly, and the wave forms became more symmetrical.

.99