Re: [amsat-bb] 5400 Rotor Trouble - HELP

[Franklin Antonio <antonio@xxxxxxxxxxxx>]

At 03:49 PM 7/20/00 -0400, Tim Pickett wrote:
>The EL rotor is turning fine, but now the meter shows 0 when
>it's down, and as you just start to come up the meter jumps to full scale.

The three sense wires for the EL rotor just go to the three terminals of a 
POT inside the rotor.  Disconnect these wires from the control box, and 
hook them to an ohmmeter.  If I remember correctly, its a 500 ohm 
pot.  Then you'll be able to see what is happening more clearly.   You 
should be able to measure a fixed resistance across two of the wires, and 
the third wire should move between 0 and max (500?) ohms to either of the 
other two.

It is possible that your sense pot is broken.

However, it is also possible that you have connected the sense wires in a 
permuted fashion.

The control box puts a fixed voltage across the pot, and then senses the 
voltage on the wiper.

Suppose you had accidentally connected the thing so that the fixed voltage 
went to the wiper, and one fixed end of the pot was being sensed.  Then, 
when the pot was at the stop at one end, you would see zero volts (as the 
voltage source is being shorted by the pot), and then as the pot moved off 
of the conductive stop, you would suddenly see something like full scale.

Permuted wiring has my vote.

Its really easy to connect these things in the wrong order, especially when 
you're on the tower!




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