Damper Resistors Calculate!

[Carl-NC]

the pot if it was adjusted whilst having a large current going thru it would certainly cause the "brushes to burn" but as they are hooked up to resistors that set a maximum and minimum, i can't see that being a problem, but would like to be enlightened!!

Even once the pot is set, it will have a large transient current going through it, and a large transient voltage across it. There's a risk of long-term damage, so I would not leave this in as a permanent way to adjust damping.

With puting a resistor in each coil to "peak" dampen each coil gets thrown out the window when you have several detectors that these coils are used on, as i recall Joe mentions of internals that have a bearing on the overall dampening of a coil and its curcuitry.

So i beg to differ on the fact that each coil needs to be dampened to fit a machine ,it's the machine needing adjustability to take any coil that is fitted to it.

Sure, this technique only works when you apply it to all coils and all detectors they are used on.

You mentioned that a Mosfet could be used, i am all ears in regards to my ..inelab machines as i make my own coils as well as using bought ones and know i can get more out of them IF i had this adjustability that was reliable.

I think Carl Nelson has a patent on using a MOSFET as a dynamic damping element. The question is, how would you automate the control to account for loop variation? I haven't given it any thought but it may not be too difficult.

- Carl

[authere]

Coil Dampening

Hi Carl,
Thanks for your wisdom,I know enough about electronics to get myself into trouble but i persist and thank you for your help.

This coil Dampening thingy has been a bugbear since i first started making coils, i would like to get to the bottom of it and have the problem solved as i think it is worthwhile as in the results do speak for themselves.

Regards Ron

PS: i look forward to you or someone coming up with some sort of solution, i found the problem but it is up to others to sort out the technical bits.

[BobCat]

Found this the other day, if it will handle the current it may be what your looking for.
Voltage controlled resistor.
For a junction field-effect transistor (JFET) under certain
operating conditions, the resistance of the drain-source
channel is a function of the gate-source voltage alone and
the JFET will behave as an almost pure ohmic resistor.
http://www.vishay.com/docs/70598/70598.pdf