Shorting coil gives back more power

[joefr]

Hi i_ron

Very nice scope shoots

Can I ask you which circuit you used to make shorting peak sine event 8 times ?

[i_ron]

On the multi short scope shot, what is the unloaded ac out voltage?

thay

6 volts AC

Ron

[Feynman]

Okay guys, I haven't gotten to coil shorting yet, but I'm about halfway through winding my electromagnet.  This takes FOREVER.

I have to superglue the damn magnet wire every 8 turns or so, then wait for it to set, then continue another 8 turns, etc, so it's really tedious!  But it's worth it to be able to control the effect I'm looking for (direction of B-field, amperage capacity of wire, number of coil layers, etc)

I'm using (I think) 26/28awg enameled magnet wire on a 5cm x 0.5cm diameter ferrite rod.  I pulled the ferrite rod from an RF choke I bought at radio shack.

Over the weekend, I also finished the PWM circuit (the 555 timer thing I posted) , which uses a 555 timer modulating a MOSFET as a low-side driver.   I can control the pulse width (aka duty cycle, from 0-100%) and I can control the frequency from about 200hz up to 100khz (depending on the timing capacitor , 0.01uF gives 200hz - 2khz, 0.001uF gives 2khz - 200khz).

My plan at the moment is to finish winding the electromagnet, then do some experiments with magnetic flux saturation (biasing the rod with permanent magnets), sort of like a magnacoaster replication.  I want to figure out how to know exactly when I've hit magnetic flux saturation in the ferrite, so I'll probably get some pins, nails , or iron filings of some kind so I can do a crude test of magnetic field strength at fixed distances from the ferrite.

I'm going hit the electromagnet with about seven 9V batteries in series connected to the MOSFET source/drain, for a total of 63V DC input pulses, of about 1% duty cycle from the 555, somewhere in the frequency of 200hz to 100khz.

Once I get that working, I'll try to set up some sort of astable trigger to short the 'ringing' in the rod so this is relevant to coil shorting, but that's about 1-2 weeks out. 

This week I'll have flux saturation results hopefully, as well as some raw data on the behavior of a pulsed DC electromagnet in ferrite vs soft iron.  (pulsed electromagnet information is surprisingly scarce).

[i_ron]

Hi i_ron

Very nice scope shoots

Can I ask you which circuit you used to make shorting peak sine event 8 times ?

Thank you!

It was posted some pages back, the zero crossing from:

http://www.8051projects.info/blogs.asp?view=plink&id=198

But here are the two parts...(first part again)

I am using the Si8410 as the replacement for an opto isolator. It takes 5 volts from the first circuit and a separate 5 volt regulator from the second circuit, so that the second circuit is completely isolated... and could be used in the highside of an H bridge. I like it

http://www.silabs.com/Support%20Documents/TechnicalDocs/si8410.pdf

J2 and J3 go across the generator coil.

Q1 and Q2 are setup as in Gyula's AC switch, posted here and on EV Gray.

Ron

[joefr]

Hi i_ron

Thanks for circuit I will try it I just need to buy missing components

I am using this circuit from Gyulasun:
http://i920.photobucket.com/albums/ad43/JoeFR/Coil%20Shorting/GyulasunCoilShorting-1.jpg

Without shorting I get this:
http://i920.photobucket.com/albums/ad43/JoeFR/Coil%20Shorting/WithoutShorting.jpg

With coil shorting I get much better results:
http://i920.photobucket.com/albums/ad43/JoeFR/Coil%20Shorting/CoilShorting.jpg

With coil shorting it charges 680uF cap to 150V quite fast

I will change two hall sensors to just one hall omnipolar sensor for more easy adjustment

Does anybody have good and reliable circuit to dump cap at preset voltage to battery (at 100v dump cap to 36v battery bank)  ?