Circuit setups for pulse motors

[capthook]

Synchronous rectifiers can offer a further 4% reduction in losses over the already efficient schottky diode rectifier.  (using individual schottky diode recitication can offer 50% reduction in losses over traditional silicon diodes/store bought rectifiers) The circuit below is for a transformer application - but could be adopted/modified for many applications.

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In this circuit, synchronous rectifiers SR2 (Q2 and D2) and SR3 (Q3 and D3) are crosscoupled to the
secondary winding of the transformer and are directly driven by the secondary voltage. Since no
driver or control circuit is used to provide the gate-drive signals, this implementation of
synchronous rectification is the simplest possible.
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Now if I only knew the required parameters for Q2/D2 and Q3/D3 and how to actually apply/build the circuit to rectify the ouput from my coils!!   

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As to the reed switch spark - I've coupled a ZNR (Panasonic part #: ERZ-V05D820) to the reed to eliminate/reduce spark.  This protects the reed switch and will result in longer life.  Also - a spark is energy being released into the atmosphere - I'd rather keep it in the circuit!

CH

[hoptoad]

Hi Hop
Could you re-post that one you deleted. I think it dealt with the use of Mosfets and I would like to see a circuit that replaces my TIP102 Darlington pair with a Mosfet. The circuit I'm using was given to me by Gyulasun who makes things simple for me and I posted it a while back.
Tropes

I can't remember what I said.....    Doh!   Maybe thats why I deleted it.   

If you're using the Opto-Coupler OPB490, (10K Pull up mode), then you should be able to simply substitute your TIP102 with an appropriate
Mosfet. The output impedance and voltage bias is perfectly suited to driving power mosfets.

Below is a link to Dick Smith Electronics (Australia).
http://dseau.resultspage.com/search.php?p=Q&ts=p2&sessionid=47e23388070637da273fc0a87f9c06ba&w=mosfets&uid=273108518&af=&ct=&site=&submit.x=13&submit.y=8

They don't carry a huge selection, but they do carry the sort of power switching Mosfets which are perfectly suited to pulsed systems. Just use the site page as a guideline to whats available. The decision to use N channel or P channel, is a matter of builder preference and / or specific circuit requirements.

The BUK456-60A has a PDF spec sheet. See link below
http://www.dse.com.au/isroot/dse/support/Z1853.pdf

Unfortunately the others seem to have broken links.

The BUK456 / 7 range of Mosfets shown on the page are high power mosfets. One is MAX rated at 600Volts  8Amps, the other is 60Volts  60Amps.

Both are ideally suited to your needs, and either one will probably be a perfect "in place" substitute for your TIP102.
If you intend to produce undamped high voltage spikes, then the BUK457-600B is the best candidate. It only handles 8A current max, but its likely you'll be aiming for currents way below that anyway.

Be sure to handle Mosfets carefully until they are installed into a circuit, because the gates are prone to electrostatic damage. Read up a little on anti static handling procedures if you're unsure. When you buy Mosfets, they should be packaged in an antistatic bag, wrap or mould or foil shield. If the outlet doesn't sell them to you with some sort of obvious shielding, then don't buy them from that outlet. They may already be damaged.

Cheers and KneeDeep 

[capthook]

.......or you could try this US electronics component supplier:

http://dkc1.digikey.com/us/digihome.html

Excellent/cheapest magnet supplier:

http://www.magnet4less.com/index.php

Wire supplier:

http://www.bulkwire.com/

CH

[tropes]

The BUK456-60A has a PDF spec sheet. See link below
http://www.dse.com.au/isroot/dse/support/Z1853.pdf
Cheers and KneeDeep 

Thanks Hop
I was able to order some BUK457-500B MOSFET's from a local supplier.
Tropes

[capthook]

Update on generator coil construction:

I have finalized my coil construction after winding/comparing 24 different styles.

Examples: All wound to the same winding dimensions 1" x 1" on 3" core.
Each coils airgap adjusted to result in similar "drag" on rotor.  3/4 x 1/2 button N42 mags N/S.

Air cores and "sheath" cores have been eliminated as output of both were sub-par.

1) #22 wire / 3/8" tap bolt:  .1 volts @ .0075 mA = 0.00075 mW

2) #26 wire / 3/8" tap bolt:  .34 volts @ 4 mA = 1.36 mW

3) #30 wire / 5/16 tap bolt with head cut off:  2.3 volts @ 21 mA = 48 mW

Smaller wire RULES for generator coils.  #1 is standard type coil - #3 is modified with smaller wire, smaller core, no head for smaller air gap.

#3 will produce 64,000 times the power over #1.

I am winding coils of the #3 variety for my project.  Custom nylon washers cut using hole saw for "bobbin" ends.  Each winding layer wrapped with 1 layer 1" masking tape.  Finished coil wrapped 1 layer electrical tape.  (rather than cutting head off bolt - you could use threaded rod - no head - I couldn't find any the right size.  A jigsaw with a metal blade takes the head off in like 20 seconds though - so no problem)

If you are going to use seperate generator/"pickup" coils in your project - try it out.  Wind #1 style then #3 style - it will blow you away!  Even bifilar - use a smaller wire for your pickup..........

I never tried "magnetite" or iron powder cores or even laminated cores.  I would love to hear from anyone who has done so and would like to share their results!

But I need to build now - enough testing already!!!

CH