Muller Dynamo

[mariuscivic]

Hi konehead
can you give me some more info about the 4421 driver?
Thanks!

[mariuscivic]

It looks good news to me.
i couldn't find the 4421 driver but i've adapted the romero's driving circuit to those mosfets and this is the result:
- The coil without shorting  is giving me around 24V
- when the shorts occurs the rpm drops a bit but it gives me instant 70V and rises around 200V
- free spining rotor 1513 rpm
-spining rotor with shorting without charging cap 1345rpm
-spining rotor with charging cap connected 1433 rpm  ( i've tryed 56....330uF/400V)

The spikes are going off the scale of my small scope

[crazycut06]

Hi Marius, nice videos,


Have you tried putting a load or a bulb at the output to see how much power you can actually use?


And how will the rotors rpm be, when loaded?




Good day!

[konehead]

Hi Mariu
Thats much better - still quite a slow-down in rpms but not too bad...try smaller caps around 100uf or so...also if try different pulse widhts if that is possible and adjsut timing a bit before and a bit after the peak, and right on top of it...
Dont do idea Crazycut jsut menitoned unless you want to see it getting snuffed out - putting resistance directly on cap being shorted into will KILL IT - this coil-shorting thing doesnt like resistance in or on the cap, or in the switching either.
You MUST discharge cap into load when also at same time cap is DISCONNECTED from the "source" which happens to be the coils being shorted. (Two stage output circuit)
I think when you get it to go to 120V instantly then you will be feeling really good - best to use real MOSFETS they dont have the high internal resistance like transistors have, and hook them up bidirectionally....put a few in paralell too for ultra-low resistance...
Also its going to be hard to measure watts-output from the cap, when you cant jsut do a lump reistive load on it, like what Crazycut, and most any engineer would want to see.
So you need to calculate watts-out from this cap-discharge formula which any EE worth their salt will agree with:
FARADS of cap /2
X
(Cap voltage before discharge SQUARED  minus the cap voltage after discharge SQUARED)
X
cap-discharge events per second
= WATTS
example:
100uf cap, that has 200V in it before discharge, and 100V in it after discharge, pulsing to load 4 times per second...
So:
100uf = .0001uf
.0001uf / 2 = .00005
200 X 200 = 40,000
100 X 100 = 10,000
40,000 - 10,000 = 30,000
so put those numbers in the formula to find watts:
.00005 X 30,000 X 4 = 6 watts

[konehead]

Hi Mariu
here is data sheet on the 4421 driver:
http://www.micrel.com/_PDF/mic4421.pdf
most any online electronics store should have them like digikey Newark, Mouser etc...
also sometimes on ebay they have some cheap -
I like the style of ones like shown in the PDF above - fairly large chips, that pop into a a 8pin socket that is soldered to circuitboard before you pop chip in,,,,

- its also nice that by using  a 4422 instead of 4421, it turns the mosfets into a normally ON switches OFF type of switch, while with 4421 driver, it is normally OFF and switches ON, so this is one way to do a two-stage output circuit; where the cap disconnects from the coils or FWBR whenever the cap hits a load.
Also interesting is that I noticed you get 100rpms more when coils short INTO cap, as compared to no cap and just coil shorting going on...this to me means if you use an even smaller uf size cap, it will work better for you...
Try mosfets bidirectional like in my circuit. because  you are switching AC oscillations....