Muller Dynamo

[plengo]

@Fausto: I am also thinking about two flanged bearings (one on each stator plate), an axis and two flange blocks holding the disk on the axis (one block below the disk and one above). The axis could be turned down to 5 mm at one end to carry an encoder wheel.

One can get flanged bearings for a 10 mm axis and also blocks for a 10 mm axis. But a 12 mm axis as you suggest is also very good.

I also observed that the bearings for a 10 mm axis or thicker have quite a high friction.

(This way of mounting the disk was chosen for the "The Muller Mark II".)

Greetings, Conrad

You're right about the friction. They are big too. I bought the 12mm more for future projects too but for this project i think even a 7mm shaft will be fine.

Fausto.

[khabe]

@khabe, I agree with you those washers give nothing besides losses. I remember Romero mentioned somewhere that when the biasing mags are too close it becomes less efficient. My conjecture is that the ferrite rods should not work under saturation.

You correct, two opposite magnets, distance between ca 35mm, what kind of saturation, what will be saturated? This tiny 6mm x 15mm ferrite rod? Why the hell it must to be come saturated? Flux concentrates out of coil, out from 35mm gap between two magnets and so what, who is waiting there - none
Someone can just walk around his room, one magnet in left hand another in right and make serial pushings between until Monday morning when needs to go to school
cheers,
khabe

[chrisC]

Hi, someone mentioned rotor height adjustment earlier, heres what i did.
http://img860.imageshack.us/img860/9404/rrotorheightadj01.jpg
http://img829.imageshack.us/img829/8135/rassembled02.jpg
http://img848.imageshack.us/img848/6374/rassembled01.jpg
A s/steel bolt with the top machined to move the rotor shaft up and down.

Awesome work you guys, some amazing constructing/testing your doing

@electroOn
Nice job! What bearings are you using and do they feel smooth?
I'm still trying to find the best ones to do the job. My VCR bearings does not have a good way to screw the assembly to the rotor for stability although the bearings are real smooth!

cheers
chrisC

[ElectronManipulator]

I posted part of this in another area, but I think it is relevant, and could help.


************
Also, I see many folks over-using diode bridges (bridge rectifiers).  When you are dealing with such low power generation, why THROW AWAY a volt and a half on each bridge??

Read up on capacitive rectification, and using MOSFETs as IDEAL (no drop) diodes.

I am by no means a know-it-all, but I see simple errors all over that could help push people a little closer to their goals on this site.

Another thing to look into would be small signal power harvesting.  It would allow you to charge caps with VERY LOW power.

You can then use a switch (optical or HALL effect) to activate a pair electro-magnets to get the boosts you need to overcome magnetic cogging.

If you have a few mA and mV to spare in this dynamo, you can charge a capacitor.  Use a XLP PIC to monitor the cap voltage and when at proper levels, attach the load, and pulse the electromagnets.  After a few cycles, disconnect the load and continue along your battery switching routing (using the PIC to handle this also) and charging the capacitor for the next cycle.

Doing this will give you MINIMAL cogging.

If you are going to continue using diodes,  use germanium diodes instead of silicon, you will gain .2v instantly on your system.  They have a lower diode drop than silicon.  This will give you what you need to use the harvesting technique.

A vibrating piezo can charge a large cap over time with these harvesting circuits.

You should really look into this.

[hartiberlin]

@khabe, I agree with you those washers give nothing besides losses. I remember Romero mentioned somewhere that when the biasing mags are too close it becomes less efficient. My conjecture is that the ferrite rods should not work under saturation.

The washers might be very important because they guide the flux
into the right direction and to finetune the distance of the magnets and the ferrite cores, so the ferrites do not get saturated from thr stator magnets.

You know you want the the flux to be switched back and forth inside the ferrite cores when the magnet rotor is passing by !