Claimed OU circuit of Rosemary Ainslie

[TinselKoala]

@Hoppy: Could you please show both traces, like I did above? The voltage drop across the current viewing shunt, Ainslie's Point B, and the voltage at the positive rail side of the inductive load, Ainslie's Point A, on the same screen at the same time?
Thanks.
--TK

(The battery capacity could be a factor here. If your battery is low or not enough amp-hour capacity the voltage will drop radically when the mosfet turns on, but your trace shows a voltage drop to zero--that cannot be right.)

Another thing is that there don't seem to be any spikes or ringdown visible. Even the stray inductances in the wires, and the built-in inductance in the mosfet, should be generating visible spikes here.

You might try using a small 18-24 volt light bulb, which will be about 3 ohms and 100 microHenries, as a load to visualize what's happening. It behaves electrically much like an actual "Ainslie load" (except for the OU of course, we couldn't have OU flashlights after all) and can be quite revealing.

[poynt99]

TK,

I believe Hoppy is measuring across the load resistor, not from V+ to gnd.

If so, then his scope shot makes sense, other than the lack of spikes. He could be using a non-inductive type resistor which would explain it.

.99

[BEP]

Which circuit are you folks talking about?

If it is the one where the load resistor is on the negative rail then putting the probe tip on the positive rail with the clip side of the probe on the positive side of the load resistor will cause a display inversion.

Nothing unexpected about that.

[Hoppy]

@Hoppy: Could you please show both traces, like I did above? The voltage drop across the current viewing shunt, Ainslie's Point B, and the voltage at the positive rail side of the inductive load, Ainslie's Point A, on the same screen at the same time?
Thanks.
--TK

(The battery capacity could be a factor here. If your battery is low or not enough amp-hour capacity the voltage will drop radically when the mosfet turns on, but your trace shows a voltage drop to zero--that cannot be right.)

Another thing is that there don't seem to be any spikes or ringdown visible. Even the stray inductances in the wires, and the built-in inductance in the mosfet, should be generating visible spikes here.

You might try using a small 18-24 volt light bulb, which will be about 3 ohms and 100 microHenries, as a load to visualize what's happening. It behaves electrically much like an actual "Ainslie load" (except for the OU of course, we couldn't have OU flashlights after all) and can be quite revealing.

I have shown the dual trace shot below at 0.2V @ 50uS

My battery is fine and the spikes are there but very faint the scope is old and the focus control is on the way out.

The resistor is wire wound but now having measured it is barely registering as an inductor on my Atlas LCR, so I will find a replacement with a higher value.

Hoppy

[Hoppy]

TK,

I believe Hoppy is measuring across the load resistor, not from V+ to gnd.

If so, then his scope shot makes sense, other than the lack of spikes. He could be using a non-inductive type resistor which would explain it.

.99

Yes, this is what I said in my post 929.

Hoppy