Muller Dynamo

[hoptoad]

Hi Romero.

I've noticed from the schematic of your circuit that you are not directly taking advantage
of the collapsing magnetic field of your drive coils when thay are in off mode.

Now there may be a good reason for this, as the introduction of feedback diodes to collect power
from the drive coils during the collapsing field event, may significantly alter the tuning of the machine. ??

But, then again, maybe you haven't tried this ??
If you have'nt already tried this, then perhaps you'd like to.

If your current operating duty cycle (on time) is lower than 30 %, then there is a very high probability that adding feedback diodes and a battery to collect the CEMF may also result in an increase in total motor torque - free of charge. This in turn may increase your total output from the gen coils?

It's an easy experiment for you to try, as it requires no tricky changes to any aspect of your current build.

Just a couple of diodes and a battery hooked up the way I've shown in a modified version of your schematic attached below ..... Perhaps you've already tried this.?

I am very curious to know how this slight addition will affect your setup. Thanks in advance if
you choose to experiment and report on the result. Understanding, if not.

Cheers from Hoptoad ..... KneeDeep

[e2matrix]

the gurus appear to have left the building temporarily 

this is the next highest amperage rating i could find in Farnell at a first pass, above Romero's existing level of current draw:

(SB1240: 12A,  40V rev,  0.45V fwd)
http://uk.farnell.com/semikron/sb1240/diode-schottky-12a-40v-axial/dp/1776353

i would have thought that a 6A (30V rev, 0.45V fwd) rating would be sufficient for a system operating at around 50Watt (motor + load), if you can find some in your usual suppliers

hope this helps
np


http://docsfreelunch.blogspot.com

Now that I think about the current rating suggested I'm wondering if you knew I was planning these for each coil (using 4 as FWBR) as the current rating seems higher than what I would have imagined.  But I'm mostly guessing and I know you understand this better but my plan for these is not at the output of all coils just for each one.  Knowing that RomeroUK's 1N4007's are only rated 1.0 amp does it sound right to need 12 amp?  Although I'm not sure what his FWBR's current rating was he paralled these on so .... I'm lost in the Amperage jungle.  lol

[khabe]

I don't understand why people are finding difficult to understand the type of wire I used.
I posted the link to my source of wires many times before.
Below is the source I bought the wire from, and the reference too:

http://wires.co.uk/acatalog/st_wire.html

7 X 0.125MM SOLDERABLE STRAND EN.Cu = 0.875mm
Ref: ST01250007-500

7 X 0.125MM SOLDERABLE STRAND EN.Cu it  IS NEVER the same like 0.875mm wire !!!!!!!!!!!!!!
Square area = 3.14 * r2
0.875 mm wire  ->  0.6      mm2
0.125mm wire   ->  0.0122 mm2

To handle at least near the same amperage you neerd to use at least 47 strands,
Perhaps now you will tell us that you do not need 25A max amperage what 0.875mm wire is able in normal motor ... (where just few meters of wire used per phase).

Then lets think about resistivity:

0.875 mm wire  ->   3 ohm per 100m
0.125mm wire   -> 136 ohm per 100m

If you do not like to think about wire square area, then about resistivity you must to think earnestly,


cheers,
khabe

[yssuraxu_697]

in the meantime i'll try the steel bolt version.

Steel bolt is basically one phat shorted turn. Do not waste time...

Dunno about EMI supression beads. In general they have pretty horrible hysteresis curve and low saturation point. Also large part of the flux will loop thru hole and not cross windings (?). But in terms of eddy currents they should be better.

One possible semi-cheap source of ferrite would be separately sold I parts of the EI transformer cores. They still have low saturation but there are ones with at least good hysteresis curve. Look for ones meant for flyback transformers.

[e2matrix]

I believe someone said they were having trouble finding the DC-DC converter.  this one is 3 amp and while it has the name 'Vanson'  it looks the same and is on sale from Maplin for Euro buyers: Universal 3A DC Power Supply Was £21.99 Save £9.00 only £12.99
On promotion until 17/05/2011   here:
http://www.maplin.co.uk/universal-3a-dc-power-supply-228639