[TowerTalk] Telrex rotator

[Ken K6MR]

Surplus Sales of Nebraska has a matching 400 Hz selsyn that will work.  As I remember you can power the units from 60 Hz power by using 12 VAC or so.  Just connect the delta windings together between the two units.  Connect the rotor windings together and apply power to the rotor windings.  If the slave unit turns backwards, reverse two of the three delta connections on one end.



What I don’t remember is if the selsyn at the rotator is driven mechanically 1:1 with the rotator on the Telrex units..  The first HyGain Roto Brake rotator also used these units, but they had a 5:1 gear system to improve the response.  I think the Telrex was 1:1, which would make building an indicator simple.



The other option for a slave display is to find what is known as a “Radio Compass”.  This is the selsyn built into a housing with a pointer and a degree wheel.  The large ones were about 5” in diameter and fit perfectly into a Collins speaker cabinet.  I have not seen one in quite a while.



Ken K6MR



________________________________
From: TowerTalk <towertalk-bounces at contesting.com> on behalf of Martin Sole <hs0zed at gmail.com>
Sent: Thursday, November 15, 2018 9:04:18 PM
To: towertalk at contesting.com
Subject: [TowerTalk] Telrex rotator

Hi,

I'm restoring a Telrex A3695RISX rotator. It's quite a monster but if I
can figure out a way to use it I think it's unlikely I would ever need
anything bigger, 1/3hp reversible AC motor, dual worm reduction gearbox,
chain drive to 3" output shaft and it weighs about 125 lbs, around 57kg.

I have no control box which poses a small problem. Wiring to the motor
is straightforward enough though I think the limit switch arrangement
could be handled better.

It uses a selsyn for position indicating. In this case actually a
General Electric Selsyn Control Transformer 2J161. This is marked
57.5-57.5 V 400CY. The device is working in that I can get the three
outputs from the stator winding when I excite the rotor winding, all
three stator outputs rise and fall with rotation so I'm pretty sure its
good.

The problem is what to do at the other end. Without a matching selsyn,
not something I expect to ever turn up around here, I am wondering how I
might be able to take the selsyn outputs and interpret them by some
other means. My understanding is the 3 stator outputs are AC voltages
varying in amplitude and with a fixed phase relationship in order to
produce an unambiguous value related to absolute position. I'm not 100%
on this yet though. They are in a delta configuration though so I'm
thinking anything I do first needs to make them Y configured

What are my options?

I had thought about an I2C compass module but that will entail placing
some other conversion hardware at the rotator to convert to something
like RS422. Any other thoughts. Just looking for ideas to think of what
might work well enough. Ideally keeping the selsyn as it's all purpose
built around that.

Martin, HS0ZED


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