It will run open for a short time, but I think that's ok if we are
shutting down.

Harold
https://w6iwi.org


On Sat, July 9, 2022 5:21 pm, hwhall@compuserve.com wrote:
> I'm curious about how to keep the sel magnet from dropping off  & letting
> the machine "run open" for the brief time until the motor to stops
> turning.
>
> WayneWB4OGM
>
> -----Original Message-----
> From: Harold Hallikainen via GreenKeys <greenkeys@mailman.qth.net>
> To: greenkeys@mailman.qth.net
> Sent: Sat, Jul 9, 2022 6:08 pm
> Subject: Re: [GreenKeys] 18 volt Internal Loop Supply
>
> On reverse polarity for motor start/stop, when in high school, my friend
> and I ran a mile of wire through trees between our houses. We ran TTY over
> that wire using ground as the other side of the loop. We had a delayed
> release current sense relay at each end and a loop supply at each end. The
> loop idled with no current. Either of us could turn on a loop supply to
> start both machines and leave a message.
>
> On my current DSP TU project, I'm thinking of just using lack of loop
> current as a motor shutdown. I'll have a loop patch box (similar to that
> at the top of https://w6iwi.org/rtty/) with a bunch of shorting 1/4 inch
> TRS jacks, an internal loop supply, a slow release SSR (resistor in series
> with loop, diode to SSR input with capacitor across SSR input), and an AC
> outlet. When there is loop current, the AC outlet is active. If there is
> an interruption to loop current (maybe 200 ms), the outlet would turn off,
> stopping the motor. This puts less I/O on the TU.
>
> Anyway, that's what I'm currently thingking.
>
> Harold
> https://w6iwi.org/rtty/DspTU/
>
>
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>>>> https://teletype.net/gksearch
>>>> 2002-to-present greenkeys archive:
>>>> http://mailman.qth.net/pipermail/greenkeys/
>>>> 1998-to-2001 greenkeys archive:
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>
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