Exactly, the point is that three relays are an intuitive means of replacing
the rotary switch. I need to learn the art of being more descriptive in
emails!
I am assuming one would bypass the rotary switch and use the three control
relays to operate the remote relays. The needed blocking capacitors are
built into the original control box so it makes sense to retain it just for
the convenience of handling the control voltages over the coax.
Yes, there are solid state switches that will pass both polarities and one
could add some led indicators to "see" that the switches are energized. I
use a Weeder Technologies board with circuits like that for antenna az/el
control of three eme antennas. I still like the audible "click" of a relay
closing though.
73,
Gerald K5GW
In a message dated 9/28/2011 8:30:24 A.M. Central Daylight Time,
jimlux@earthlink.net writes:
On 9/28/11 6:13 AM, TexasRF@aol.com wrote:
> Hearing and seeing a relay close is reassuring. That aspect is lost with
> solid state switches.
> A relay is very tolerant of voltage levels, current, and polarity. A
> bulletproof device if there ever was such a thing.
> Use of three relays allows close duplication of the original control
> circuit. One for +, one for -, one for both and none for the default
> state. Only one relay at a time needs to be operated making the control
> logic quite straight forward.
The control box doesn't have any relays, just a rotary switch.
The box at the antenna does have relays, but I don't think anyone is
contemplating changing that. There are also multiple versions of the
RCS-4, for what it's worth (one has 3 relays in the remote box, the
other has 2).. but the control scheme is the same. half wave rectified
AC as one bit of control, the other polarity as the other.
There is an advantage of using a pair of small SPST relays as the
interface between computer and remote box, and that has to do with
providing galvanic isolation. One less place for a ground loop, etc.
there are some small, cheap solid state relays that would work, too (or
optoisolated SCRs)
You'd have to decode the diode indicators some other way, of course.
> KISS works for me!
> 73,
> Gerald K5GW
> In a message dated 9/28/2011 7:47:12 A.M. Central Daylight Time,
> jimlux@earthlink.net writes:
>
>
>
> You only need 2 relays at most. (at least to actuate the remote
relays)
>
> A pair of SCRs? (and some diodes) I haven't had my coffee yet, so I
> can't think of how you'd arrange to get them biased corectly.
>
> A triac, with the gate pulse timed right after the zero crossing.
>
> >
>
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