[GreenKeys] ASCII/RS-232/AFSK Interface for the Model 15 Teletype

[Paul Heller]

A brilliant design. I’m not totally able to follow all of it - you guys are way ahead of me - but it has been fun to hear some of the theory. 

I chose computer science but always wished I knew more electrical engineering then I currently do. Need any coding?

Keep the great stuff coming, guys. 

Paul


> On Jun 26, 2022, at 3:41 PM, Mike Douglas via GreenKeys <greenkeys at mailman.qth.net> wrote:
> 
> Harold,
> 
> The HM selector is about 55 ohms and the PM selector is closer to 220 ohms.
> 
> R11 is only in circuit if the TTY is not plugged into the connector. R11 allows the voltage built up on C1/C2 to decay during marking states.
> 
> Yes, AFSK audio goes into a comparator, the output of which then goes to an input capture module to time cycle periods.
> 
> Mike
> 
>> On Jun 26, 2022, at 11:45 AM, Harold Hallikainen via GreenKeys <greenkeys at mailman.qth.net> wrote:
>> 
>> Nice! Why the different values of R2 for holding and pulling magnets?
>> Maybe the lower resistance of holding magnet coils in parallel?
>> 
>> What is the purpose of R11 across the selector magnet?
>> 
>> It looks like the AFSK input is going to an analog comparator input. Is
>> this using period timing to demodulate the AFSK?
>> 
>> Nice work!
>> 
>> Harold
>> https://w6iwi.org
>> 
>> 
>>>> On Sun, June 26, 2022 9:34 am, Mike Douglas via GreenKeys wrote:
>>> I recently made a new version of the subject interface board that
>>> incorporates the changes I made to the prototype unit that you may have
>>> seen in a few videos I posted. I've made a web page to document this new
>>> version - see the link below. I still need to write a user manual and
>>> finish a small wish-list I've given myself for the firmware.
>>> 
>>> https://deramp.com/model15_interface.html
>>> 
>>> I have a number of bare PCBs of this new version if anyone wants one -
>>> just contact me. I'd still like to work with someone to tweak components
>>> and firmware as needed for a holding magnet configuration.
>>> 
>>> Mike
>>> 
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>>>>>> Jordan Spencer Cunningham's GreenKeys Search Tool:
>>>>>> https://teletype.net/gksearch
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>>>>>> http://mailman.qth.net/pipermail/greenkeys/
>>>>>> 1998-to-2001 greenkeys archive:
>>>>>> http://mailman.qth.net/archive/greenkeys/greenkeys.html
>>>>>> Randy Guttery's 2001-to-2009 GreenKeys Search Tool:
>>>>>> http://comcents.com/tty/greenkeyssearch.html
>>> 
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>>> 
>> 
>> 
>> -- 
>> FCC Rules Updated Daily at http://www.hallikainen.com
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>> 
>>>>> Jordan Spencer Cunningham's GreenKeys Search Tool: https://teletype.net/gksearch
>>>>> 2002-to-present greenkeys archive: http://mailman.qth.net/pipermail/greenkeys/
>>>>> 1998-to-2001 greenkeys archive: http://mailman.qth.net/archive/greenkeys/greenkeys.html
>>>>> Randy Guttery's 2001-to-2009 GreenKeys Search Tool: http://comcents.com/tty/greenkeyssearch.html
>> 
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> 
> ______________________________________________________________
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> 
>>>> Jordan Spencer Cunningham's GreenKeys Search Tool: https://teletype.net/gksearch
>>>> 2002-to-present greenkeys archive: http://mailman.qth.net/pipermail/greenkeys/
>>>> 1998-to-2001 greenkeys archive: http://mailman.qth.net/archive/greenkeys/greenkeys.html
>>>> Randy Guttery's 2001-to-2009 GreenKeys Search Tool: http://comcents.com/tty/greenkeyssearch.html
> 
> This list hosted by: http://www.qsl.net
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