Confirming the Delayed Lenz Effect

[conradelektro]

@Conrad: Why in the world are you using a P-channel mosfet in that circuit? The equivalent or even better rated N-channel mosfet would be cheaper and more "logical" in that single-transistor "high side switch" circuit, wouldn't it?

@TinselKoala: your statement made me think and try a N-Channel MOSFET with my Hall sensor.

( Version 1 of my ring magnet spinner, see e.g. at http://www.overunity.com/11350/confirming-the-delayed-lenz-effect/msg359105/#msg359105 )

My Version 1 of the magnet spinner works also with a single N-Channel MOSFET, but it is slightly less efficient because the Hall Sensor is about 55% High and 45% Low per turn of the ring magnet. So, in the N-Channel version the current flows a bit too long (in comparison with the P-Channel version).

But in practice that does not matter much, one would use the N-Channel MOSFET because it costs less and has a lower on-resistance.

I also played with a trigger coil:

The MOSFETs are not suitable for a trigger coil because they need up to 5 V at the base to switch on completely. It works with a trigger coil, but only at high rpm and the thing is difficult to start. I have to try a trigger coil with an ordinary NPN transistor (which switches on e.g. at 1 Volt at the base).

Greetings, Conrad

[TinselKoala]

@Conrad: thanks for the response and the experiment... but....
The N-channel mosfet is usually installed with the drain towards the positive rail and the source (source of electrons) to the negative rail. In other words, use the bottom schematic, not the top one, but put the N-ch mosfet in with the Source pin to the negative rail and the Drain pin to the low side of the load, and the high side of the load to the positive rail. The mosfet, when on, will conduct in both directions, but you may see a difference in turnon times with the arrangement I suggest. I doubt if it will make a significant difference in your pulse motor, but it's normal practice with N-ch mosfets to connect the Source pin to the common negative (ground) rail of the circuit.
The 5.6 K pullup resistor value may also be increased, or even changed for a pull-down (connect to negative rail instead of positive) for significant effects on the circuit performance.  I usually use a pulldown, connecting the gate to the source right at the mosfet pins with a suitable resistor like 100K.

ETA: Never mind, I'm seeing things again I guess, since the bottom diagram now looks correct to me. But consider the resistor function and experiment with a pulldown instead of a pullup.

Also, you could use a bipolar transistor with a pickup coil and use its output to trigger the mosfet...

[Farmhand]

Sorry Mags I know you only want to help. OK guys, this is the arrangement of my motor circuit, showing the current sense resistors I have in place at the moment. Any suggestions ? I'll need to scope the current into the coil at the same time as I scope the drain waveform I guess ?

To explain the operation, after the first pulse the charging coil discharges into C2 which charges it to about 20 volts when 12 volts supply is used, then on the next pulse the capacitor C2 discharges through the motor coil, then the charging coil recharges the capacitor C2 and the cycle repeats. So the charging coil is lagging in phase to the motor coil and the motor coil supply (C2) goes to almost Zero volts, if I use a snubber there it will try to charge the capacitor C2 which is at zero volts and that is no good, it doesn't work well like that.

In the circuit how it is configured now when the motor coil is discharging it still aids to charge the capacitor "C2" because the charge battery is in series with the charging coil then C2, doesn't it ? That is where the charging coil discharges into. But if I try to connect directly the flyback diode to the capacitor C2 or even directly to the charging coil some performance is lost. I've already done the experiments but informally. Mags I can show you if you wish.

The drawing might explain help explain the wave form shown above.

Cheers

P.S. I wasn't able to draw a 45 degree coil quick enough, so I drew it how I made it originally before I used the charging coil to aid the rotation, and showed point "A" and "B" for where the charging coil can be placed.

Ok there's the shots, the top two are the snubbed ones with diode connected back to the coil and the bottom two are the way the drawing is. The pulse width remained the same and snubbed the frequency was quite a bit lower as can be seen. My conclusion is it's better to discharge the inductive energy into a higher voltage.

Yellow trace is the current through a 0.1 Ohm resistor (R2) and the Blue trace is the drain of the mosfet with the scope grounds together.

Bottom left shot is a false trigger, I'll try to get a better one and fix the picture. The pulse width is fixed at 3.16 mS and I do not change it, I can video it if necessary.

Oh please note that I had to change the volts per division for the blue trace in the bottom shots from 10 to 20 to fit it in.

My discharge voltage and current wave forms fit together like hand in glove, so Mag's you were right in that way for my setup I think, but it was to my benefit anyway so I'm stoked with the wave forms of the motor, I wonder what the peak currents and power were for the charging/aiding coil.  The input power varied very little.

However with the snubber the current in the coil stops immediately.

..

[conradelektro]

@Conrad: thanks for the response and the experiment... but....
The N-channel mosfet is usually installed with the drain towards the positive rail and the source (source of electrons) to the negative rail. In other words, use the bottom schematic, not the top one, but put the N-ch mosfet in with the Source pin to the negative rail and the Drain pin to the low side of the load, and the high side of the load to the positive rail. The mosfet, when on, will conduct in both directions, but you may see a difference in turnon times with the arrangement I suggest. I doubt if it will make a significant difference in your pulse motor, but it's normal practice with N-ch mosfets to connect the Source pin to the common negative (ground) rail of the circuit.
The 5.6 K pullup resistor value may also be increased, or even changed for a pull-down (connect to negative rail instead of positive) for significant effects on the circuit performance.  I usually use a pulldown, connecting the gate to the source right at the mosfet pins with a suitable resistor like 100K.

ETA: Never mind, I'm seeing things again I guess, since the bottom diagram now looks correct to me. But consider the resistor function and experiment with a pulldown instead of a pullup.

Also, you could use a bipolar transistor with a pickup coil and use its output to trigger the mosfet...

@TinselKoala: you are not seeing things, I changed the drawing a bit later because I noticed the error with the Drain of the N-Chanenel MOSFET (error was only in the drawing, a copy paste error). I will try the pull down 100K resistor at the base of the MOSFET. But I am not sure whether my Hall sensor needs a pull up resistor for clean switching.

Trigger coil and MJE13007:

I did some tests with a trigger coil (the trigger coil and the two drive coils are identical).

The efficiency is about the same as with these circuits http://www.overunity.com/11350/confirming-the-delayed-lenz-effect/msg359277/#msg359277 ,
but I can go up to 30 V which gives me 10800 rpm for 1.5 Watt.

But the vibrations are very strong at 10800 rpm , so, I will stay at 6000 rpm for future magic coil tests. (The mechanical problems are not easy to solve; one needed to balance ring magnet and axle, the ball bearings have to be fitted very precisely; all this is beyond my skills).

The trigger coil has a draw back. Starting the ring magnet spinner is not easy because the trigger coil needs to generate about 2 Volt to start things going. One can start by holding the trigger coil closer to the ring magnet and then when it span up one places it further away to avoid drag. This is of course not practical, so, a Hall sensor might be better.

I will try the transistor MJE13007 with the Hall sensor (needs a resistor to limit the base current from the hall sensor output).

Greetings, Conrad

[conradelektro]

@Farmhand: thank you for posting the very clear circuit diagram. Interesting, the position of your charging coil corresponds to the optimal position of the trigger coil in my last test (see my above post).

Greetings, Conrad