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HighVoltage
Apr 23, 2004, 04:41 PM
I have this ideal for electric helis and I wonder if anyone has tried it.

With regard to brushless motors, has anyone seen a DIY controller built like this ? (see below)

The function of the controller is to break up a full DC source into a stepped sine wave. Currently one battery pack used at full voltage is used to supply this gizmo with power.

But the power is already divided in the batteries. If you arrange a pack as 1 cell for the lower level DC voltages required to generate the stepped DC & 4 cells for the higher voltage. With these supplies available all you need is some gates and some FFT's to produce a single sine at the output.

The three phase workup of this may require 2 or maybe even 3 sources. A CD ROM motor could be made to work in single phase if it can be re wired.

I'm curious if anyone has any comments about this idea or know if its been tried or would want to build the circuit that you or I design to test it. It is too difficult to build a board and do electronic testing in my apt. My place cannot make room for any more new stuff- particularly since the heli.

HighVoltage
Apr 23, 2004, 04:44 PM
I don't know if a CD ROM can be rewired to single phase. Does anyone ?

Motors are a vague memory for me. I graduated eng about 7 years ago and not in that field.

tim hooper
Apr 23, 2004, 06:38 PM
Doug,

I'm moving this to the DIY forum.......

tim hooper

vintage1
Apr 23, 2004, 07:29 PM
Single or 2 phase motors will run equally well inboth directions, so are not ideal.

Its simpler to use the conventional 6 FETS for a 3 phase controller. Switching the fets on is not a big issue. Sensing WHEN to switch them on, is.

Its a big project to make a brushless controller. There are a few designs out there.

AndyOne
Apr 23, 2004, 07:33 PM
Doug,

The problem with tapping batteries for different voltages is that it unbalances the cells as it discharges the lower voltage ones in the pack more than the higher ones. Apart from not being very efficient use of battery power, this is the last thing you would want to do with a lithium pack where cell balance is everything.

Andy.