[amsat-bb] Rotator rebuild with stepper motor

Angus angus at young5769.freeserve.co.uk
Sun Feb 15 11:43:39 PST 2009

Hi all, 
got given today an old rotator, looks OK with only a little weathering but 36 volt motor is burnt out completely.
Apparently the owner had bought it to turn an 9 ele 2mtr yagi but after a year it was turning 6mtr beam, 4 mtr beam, 2 x 2mtr beams and 4 x 70cm yagis and yes you guessed it, first good wind it burnt out the motor.
I had the unit apart and the gears look fine, as does everything else except the motor which is completely dead.
I have over the last 2 years been building and using a homebrew PCB mill complete with stepper motor interface and control software etc.
OK my thoughts are replace the AC motor with a good large stepper motor (I gathered loads up whilst building my mill) and fit that into the housing and build a completely new drive interface.
The idea is that the rotator should now have a stronger motor and also being a stepper motor it should try and resist any movement whilst not in motion (whilst powered up), also as an added bonus I should be able to control the speed of rotation far more than a normal AC motor and almost have very small steps whilst tracking a satellite and then speed the whole thing up when I want to move to another satellite.

OK has anyone done this and if so what problems did they face, or does anyone have any suggestions on what to do and what not to do.

The unit was free, I got a large lump of a stepper motor doing nothing and a little time on my hands so not going to cost anything (in relative terms), so it must be worth a try.
Knowing what my mill is like the unit could be positioned very accurately and track at a really nice slow almost step less rate.

So got to be worth a try?

any thoughts


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