[GreenKeys] Regenerative Loop Driver for Model 15 Teletype

[Gerry Block]

Mike that is a beautiful board. 
Have you looked at the selector magnet current that your design provides using a current probe??
Gerry

Sent from my iPhone

> On Dec 8, 2021, at 6:57 AM, Mike Douglas via GreenKeys <greenkeys at mailman.qth.net> wrote:
> 
> 
> You can see what I presently have running here: https://deramp.com/downloads/teletype/Model%2015/loop%20interface%20board/
> 
> Mike
> 
> On Tuesday, December 7, 2021, 09:41:41 PM CST, Harold Hallikainen <harold at w6iwi.org> wrote:
> 
> 
> Very nice! It would be  interesting to see a schematic of the loop keyer.
> 
> Harold
> 
> 
> On Tue, December 7, 2021 6:51 pm, Mike Douglas via GreenKeys wrote:
> > I  have a new 60ma loop driver for the Model 15 (and related units) up and
> > running that does not require a high voltage supply, nor does it include a
> > switching supply to generate a high voltage. Instead, a regenerative
> > approach is used in which the snubber circuit for the selector magnet coil
> > captures the energy from the mark to space transition and then dumps that
> > energy back into the selector magnet during a space to mark transition.
> > This allows operation of the interface board from a 15v power supply
> > which, in turn, allows it to dissipate very little heat.
> >
> > The board provides two 1/4" phone jacks for connecting the printer and
> > keyboard cables from the Model 15. Host connections include RS-232 (DB-9
> > or DB-25 via RJ14 modular connectors) and a 3.5mm audio jack for
> > connecting an AFSK feed (e.g. ITTY). A barrel jack is provided for
> > connection of a 15v AC adapter,
> >
> > The RS-232 host connection uses ASCII at 9600 baud and includes a
> > handshake line to automatically throttle the sending computer. With a
> > terminal emulator, it's just a matter of turning on the "hardware
> > handshake" checkbox. For vintage computers (e.g., Altair, IMSAI, etc.),
> > virtually all serial boards bring out the CTS pin of the UART to the DB-25
> > and that will throttle the transmitter without any software changes. This
> > allows the host computer to use ASCII at a standard baud rate instead of
> > having to worry about five bit/45.5 baud support.
> >
> > Presently, I have ASCII-Baudot translation tables installed for ITA2-TTY
> > and USA-TTY. I've also added the ability to generate ASCII keycodes that
> > can't be generated by the Model 15 keyboard by defining an escape sequence
> > starting with the blank key. The board allows full or half duplex
> > operation and also provides a 5-bit pass-through mode (5 bits within each
> > byte).
> >
> > The audio interface demodulates AFSK (presently mark 2125 Hz and space
> > 2295 Hz as used with ITTY) and sends the demodulated output directly to
> > the printer.
> >
> > A configuration menu is entered if ESC is pressed on the host side within
> > 3 seconds after power-on. The menu allows selection of which ASCII/Baudot
> > translation table to use, enabling  a 5-bit pass-through mode, updating
> > the firmware, etc.
> >
> > I will soon be putting up a video on YouTube that shows a Model 15 in use
> > as the console for an Altair 8800 computer. This provides a good
> > demonstration of the Model 15 as well as the ASCII interface capability of
> > the loop driver.
> >
> > Mike
> 
> > ______________________________________________________________
> > GreenKeys mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/greenkeys
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:GreenKeys at mailman.qth.net
> >
> >>>> 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
> > Please help support this email list: http://www.qsl.net/donate.html
> > Message delivered to harold at w6iwi.org
> >
> 
> 
> -- 
> FCC Rules Updated Daily at http://www.hallikainen.com
> Not sent from an iPhone.
> ______________________________________________________________
> GreenKeys mailing list
> Home: http://mailman.qth.net/mailman/listinfo/greenkeys
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:GreenKeys at mailman.qth.net
> 
> >>> 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
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to deramp5113 at yahoo.com
> 
> ______________________________________________________________
> GreenKeys mailing list
> Home: http://mailman.qth.net/mailman/listinfo/greenkeys
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:GreenKeys at mailman.qth.net
> 
>>>> 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
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to gblock at sbcglobal.net
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/greenkeys/attachments/20211208/cedfd417/attachment.html>