Forward EMF Collection

[Dave45]

Yes you can us a resistor in the circuit after the coil, I did it works either way you will still get bemf hitting the meter.
We think of diodes as a one way valve but actually there not in that they let pos energy flow one direction and neg flow the other.
We tend to think of electricity as water flowing in a pipe, this is a mistake water does not flow in two directions at once.
When lightning strikes there are two leaders one from the neg charged ground and one from the pos charged clouds.

[d3x0r]

Yes, when the switch opens, the coil side goes positive...


that is it has a supply of electrons near 0 potential/density... when the switch opens, the current in the coil cointinues...which removes the electrons from near the switch, which makes it positive....  or if the current is in the other direction, the current will continue towards the switch which will make that side negative....


It's always about one thing flowing; if there are two aspects, it's electro-magnetic and electro-static (dielectric)...

[Dave45]

try to connect the earth to the core

Connect one core neg and one core pos

[dieter]

If we pulse a coil and catch the bemf we get pos energy - cold current - pure voltage Iv heard it called many names but it has no use, ...

I'm not sure of that. First of all, if it doesn't take energy to cause a pure voltage, why isn't everything at high voltage 24/7? So, it must take energy. Where does that come from?


An other aspect: here the word for voltage is "Spannung" which means Tension. It says a lot. Think of sparks and arcs. The higher the tension, the longer the arcs trough the air. Dynamic tension is energy manifestation IMHO. A voltage runs ahead of the current trough a coil, the current follows due to tension.
One thing I would definitely suggest to try is: connect your bemf to a good ground. I don't agree with the bemf running fwd, sorry. That's why it's named BACK emf.


There is some sort of problem when you try to redirect the bemf with diodes. They work well to block it from the fwd source, eg. fragile CMOS for protection.


But the redirection is a diffrent thing. Because the bemf manifests at the coils IN side, but is then blocked. Any direction it can flow from here may also be used by the fwd pulse. That's the dilemma. But there's an old trick: A sparkgap! So the fwd current will not use the sparkgap because A the coil is easier and B because the voltage is lower, the bemf on the other hand is blocked by the supply diode and is forced to jump accross the gap. 500 to 1000 volts required (I used a moskito trap, runs on 3V). AC is a bad choice for bemf stuff. short square dc pulses work best. Simple to implement with a spark gap, probably use tungsten or so to keep it service free. Back emf voltage of fwd 1kV may be 4kV, so use HV diodes and caps. 5 normal 1kV diodes in series substitute a 5kV diode.
So, this is the idea: redirect the bemf with said sparkgap and see it as you new plus pole. at the other end of the coil (that is already connected to supply minus) add a diode that goes to ground 1. This will become your positive bemf current source. After the "Bemf-gap" add a load and after that connect to ground 2, the bemf current negative source, a few meters away from ground 1. Also add blocking diodes after the supply, so the bemf does not try to draw positive current from the supply negative side.


Not sure if it works, but it fried my digital multimeter after showing hundreds of amperes, inconsistently jumping around :-) so be careful.


I will try this again.


Regards

[dieter]

Here's a little sketch of what I'm talking about...