[GreenKeys] Affordable current loop adapter

[John, W9DDD]

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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-- 
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The above comments or recommendations are SWAG. Use at your own risk.

John, W9DDD

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