[amsat-bb] Re: rotor replacement pots

SV1BSX sv1bsx at yahoo.gr
Thu Sep 18 05:09:37 PDT 2008

Hi Domenico & George, Hi all,

another cheap solution is the AS 5040,  however  the SSOP-16 package of this
IC is a problem
for homebrewers, as the chip is very tiny and always needs a good PCB with
high accuracy
between the tracks. In addition is necessary to make some mechanical
construction in order
to support the moving-magnet and the circuit,  in place of the 

 This IC working with digital -or- analogue output if you want a standalone
device  (0-5Volts for 0-360 degrees or by using a divider : 0-3.6 Volts
for a direct digital readout).

A few nice examples you can find here:



However I completely agree with Domenico, the classical wire pot is the
best techical and economical solution for Satellites. All the rest are much
more complicated, and they need dozen-hours of experimentation.
 OK, even if the pot needs replacement from time to time, for me
remains  that a simple, easy and comfortable solution for our applications.
And keep in mind, the POT is a "passive" component in contrast with any
IC into the rotor, which is an active circuit into a non-friendly 
that inside of metal case of rotor,  where extreme temperature take place
between -35  on N.Europe, Canada etc and  upto 80-90  Celsius on South
areas !.

No very comfortable environment's condition for an IC - even if has a low 

73, Mak SV1BSX

> Has anybody tried to use other methods of sensing than the pots? I'm
> currently trying an electronic compass. First results are promising.
> Eventually I want to completely replace the Yaesu controller.
> BR,
> --
> /\/\arc

Hi George, ON4AMV

It is possible to use commercially available absolute encoders with
linear analog output from 0 to 5 volt or from 0 to 10 volt for a single
revolution of 360°

The above absolute encoders are more accurate than any conventional
linear 360° potentiometer and they don't use moving contacts like a
wiper built into a wirewound potentiometer.

They are made by Tekel, Eltra, Lika Electronic and many others manufacturers
for robotics and industrial application but they are very expensive.

In addition the backlash into the gears of a G5400 rotator do not justify
such high accuracy and a good wirewound linear 500 ohm potentiometer
represents the best technical and economical solution.

By the way when a very high repeatedly position accuracy is requested
as for large EME dishes then absolute encoders or resolvers with the
associated syncro to digital converters are necessary.

73" de

i8CVS Domenico

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