[GreenKeys] Affordable current loop adapter

[Jeffrey Golas]

Which one?

Jeff

> On May 18, 2025, at 11:09 AM, John, W9DDD <w9ddd at tapr.org> wrote:
> 
> It's been tested with a 28.
> 
> 
>> On 5/18/2025 8:21 AM, Jeffrey Golas wrote:
>> I believe he said the model 15 one depends on the actual 25 selector coils so it wont work with others except maybe a 14.
>> 
>> The 33 one may work but Its prob hard wired for 110 baud?
>> 
>> A 20ma current loop transmitter may work if you can find a way to feed it data, say from fldigi.
>> 
>> The fastest cheapest easiest test would be the arduino one on Hackaday using a relay. It works!
>> 
>> I think this one: https://hackaday.io/project/2836-arduino-teletype
>> 
>> Jeff
>> 
>> 
>> 
>>>> On May 18, 2025, at 8:19 AM, John, W9DDD <w9ddd at tapr.org> wrote:
>>> 
>>> 
>>> 
>>> Actually the M15 adapter would be a better fit.  Same designer, same source.
>>> 
>>> 
>>> https://deramp.com/model15_interface.html
>>> 
>>> 
>>> Tested on one of my 28s by Mike, don't know whey I didn't think of it when the question was originally posted.
>>> 
>>> 
>>> On 5/18/2025 2:20 AM, Erik Grant wrote:
>>>> While this one is for the M33, it might be worth while to contact this guy @ https://deramp.com/tty_adapter.html <https://deramp.com/tty_adapter.html>
>>>> Teletype RS-232 Adapter - DeRamp.com <https://deramp.com/tty_adapter.html>
>>>> The Teletype RS-232 adapter comes fully assembled and tested as shown in the pictures on this page. A telephone cord and modular DB-25 connector are not included.Version "B" of the board is now shipping.
>>>> deramp.com
>>>> 
>>>> 
>>>> ~KF7WAI
>>>> 
>>>> ------------------------------------------------------------------------
>>>> *From:* greenkeys-bounces at mailman.qth.net <greenkeys-bounces at mailman.qth.net> on behalf of Tim McNerney <mc at media.mit.edu>
>>>> *Sent:* Thursday, May 8, 2025 9:52 AM
>>>> *To:* greenkeys at mailman.qth.net <greenkeys at mailman.qth.net>
>>>> *Subject:* [GreenKeys] Affordable current loop adapter
>>>> I need to test my 28RO.
>>>> Most of the RS-232 to 20 mA current-loop adapters are "wicked expensive."
>>>> Plus nowadays, RS-232 is not exactly easy to find as an interface.
>>>> So I'll be up to $200 before I finally connect to a computer via USB.
>>>> And of course USB to current-loop... good luck finding that adapter...
>>>> 
>>>> Can anyone recommend a circuit for a simple 20 mA current loop transmitter?
>>>> I have EE and soldering chops.  Happy to build my own prototype.
>>>> 
>>>> BTW, I've noticed lots of affordable 4-20 mA current loop transmitters
>>>> for remote industrial sensors.
>>>> Can these be adapted to serve as a 20 mA digital transmitter?
>>>> Intuition makes me think yes, but I want to double-check.
>>>> Maybe 4 mA does not equal "0".
>>>> 
>>>> Thanks.
>>>> --Tim McNerney
>>>> 
>>>> 
>>>> 
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>>> John, W9DDD
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> --
> ---
> ----
> The above comments or recommendations are SWAG. Use at your own risk.
> 
> John, W9DDD
>