user TURBO?s replication of Steven Mark?s TPU ?

[z_p_e]

This is what I suspect will be seen with the test, and with the bulb wire going outside the coil, not inside. Whether there is a difference with the wire running inside the coil remains to be seen from actual test results.

When the MOSFET is ON, there is a voltage division between the coil's series resistance (0.5 Ohm) and the ON resistance of the MOSFET.

When the MOSFET turns OFF, there is a cemf spike (100's of volts), and the voltage across the bulb goes to the full 12V because the MOSFET is no longer pulling down the voltage.

I have calculated the 50-turn coil inductance to be approximately 100uH, and the series resistance to be 0.5 Ohms. Also, the bulb resistance I set to 50 Ohms. These are approximate values, and changing any of these variables of course changes the peak voltage of the cemf spikes etc, but the picture remains more or less the same.

I used a frequency of 200Hz, 50% duty square wave.

If anyone would like to suggest any different values for any of the above, I'd be glad to re-run the simulation...it only takes a second.

Conclusion: There is nothing new or unusual about these results. Maybe the actual test will reveal something different.

Darren

[starcruiser]

Try it with 170 turns of 26AWG for the control. the rest can be the same.

Let us us know what you get please.

[z_p_e]

Starcruiser, I assume you're talking to me?

If you or someone could measure your coil resistance and inductance, that would be far easier and accurate. As a minimum, measure the resistance. Providing the coil length, radius, and how many layers, and turns per layer if possible would be great.

I hate guessing if I can avoid it. Give me numbers please.

In the mean time, I'll see if I can figure out an approximate value of inductance and resistance for this request.

Darren

[z_p_e]

OK, I did a quick and rough calculation of the new Inductance and Resistance with 176 turns of #26.

Inductance ~ 517uH
Resistance ~ 1.76 Ohms

Spikes now peak out at 240Vp.

Darren

[starcruiser]

zpe,

is that per control coil or layer?