[GreenKeys] Teletypes at the Maker Faire
Jordan Spencer Cunningham
js at cunni.co
Sat Apr 21 21:42:52 EDT 2018
The USB to current loop adapter I built took care of converting plaintext
(ASCII) to Baudot at 45 baud. It's capable of doing so I believe up to
around 1200 baud maximum if I recall correctly.
I built the adapters using Eric Volpe's design found here:
http://heepy.net/index.php/USB-teletype
On Sat, Apr 21, 2018, 4:28 AM info at drukknop.nl <info at drukknop.nl> wrote:
> i am very interested in how you managed to get 45.45 going on the raspi.
>
> On 21-04-18 08:52, Jordan Spencer Cunningham wrote:
> > Thanks everyone.
> >
> > There have been some off-list questions about the entire setup,
> > particularly about what I have running on that board of electronics
> > between the two teletypes. Since several people were curious, I figure
> > I'll share with the entire group. Attached is an aerial view of the
> > setup, and below is an explanation that may interest or inspire you for
> > your own builds. Apologies to those who automatically print out
> > Greenkeys since this is a lot of text.
> >
> > * I didn't have enough time to design and fabricate a permanent
> > enclosure for the system, so it's exposed and simply mounted on two
> > pieces of wood I had lying around the basement. I plan to design
> > panels and have them cut with my brother's CNC machine, after which
> > I will assemble them into a box and mount everything inside, but
> > that is a ways out.
> > * There is a surface-mount, bakelite-style, round power switch on one
> > side that controls power for the entire system. When this is turned
> > on, 120VAC power is distributed to a 5VDC power supply and various
> > relays that are normally open.
> > * The 5VDC power supply gives power to a Raspberry Pi and the main
> > electromechanical relay board. This power supply is the smaller
> > silver box.
> > * Stacked on top of the Raspberry Pi is a "hat" that distributes the
> > GPIO pins into screw terminals for easier wire connections.
> > * The Raspberry Pi is programmed using my own software (eventually I
> > will release it to the general public for free use, but I have a lot
> > more I want to perfect first); currently it is capable of the
> following:
> > o Someone can flick a momentary switch that is connected to the
> > Raspberry Pi's GPIO pins, and that will trigger the Pi to turn
> > on the requested teletype and current loop via relays. The Pi
> > will thereafter listen for input from the teletype so the
> > operator can execute certain commands. The teletype and loop
> > automatically turns off if no input is received after so much
> time
> > o The operator can execute commands to send an email, send SMS
> > messages, and select and print out from presaved ASCII/ITA2/RTTY
> > art (or whatever technically correct name you want to call it)
> > o The Raspberry Pi checks for new email and SMS messages every 2-3
> > seconds (this is configurable); if a new message is detected, it
> > will parse it and make it teletype friendly, turn on the
> > appropriate teletype, and cause the message to be printed out
> > o I will be adding support for ITTY, RSS feeds, direct TCP
> > connections, and hopefully i-Telex eventually. I also would like
> > to add support for all transmission methods to be optionally
> > encrypted via an OTP tape mixer emulation and an Enigma
> emulation.
> > * The Raspberry Pi is connected to two USB <--> 20/60ma loop boards
> > that I built after Eric Volpe's design
> > o Each Volpe board is connected to a separate current loop, which
> > is connected to a separate teletype (very special thanks to Paul
> > at RTTY Electronics for having the 1/4-inch plugs and mounts in
> > stock)
> > * The Raspberry Pi's GPIO pins also control the electromechanical
> > relay board, and I've programmed functions to turn those relays on
> > and off; these functions are called by my software as needed to
> > control the physical system.
> > o Two relays control 120VAC power to each of the teletype motors
> > o One relay controls 120VAC power to the 0-150VDC power supply
> > (this PSU is currently calibrated to serve 120VDC on the current
> > loops; eventually I will also power my M19's tape punch off of
> > it, but I need to fix a few things on it first). This is the
> > largest silver box.
> > o Two relays control 5VDC power each to trigger two solid state
> relays
> > + These two solid state relays control power on each current
> > loop so that if only one teletype needs to run during a
> > given time, only one loop will be turned on. The Pi could
> > have driven the SSRs directly since they'll trigger with as
> > low as 3VDC, but I had my reasons for doing it this way with
> > 5VDC instead.
> > * Each current loop is equipped with a 10W resistor to limit the
> > current and a 62.5ma slow-blow fuse. I chose to add a fuse because
> > at one point during construction of the system I accidentally had
> > too much current going through the selector magnets of one of my
> > machines, and they started to smoke due to the shrinkwrap on the
> > outside of the coils overheating. Luckily I cut power before
> > anything catastrophic happened, and the magnets still work perfectly
> > fine. I was probably drawing 200-230ma through the loop at that time.
> > * The plugs that supply power for the teletype motors are also in the
> > old surface-mount bakelite style, like the switch.
> > * When away from home, an internet connection is supplied from my
> > phone connected directly to the Raspberry Pi over USB. Under normal
> > circumstances I have it connected via ethernet to my home network.
> > * The MacBook you see in the Faire pictures is connected directly to
> > the Raspberry Pi over ethernet; I'm simply SSHed into the Raspberry
> > Pi this way to show the logs scrolling past. It isn't necessary for
> > the operation of the machines-- it's just for show.
> > * The wire nuts you see are on one of the loop plugs for my M19; one
> > of the cables got severed at some point before I got it. Despite
> > ordering old style braided nylon-insulated 18-2 replacement cable, I
> > haven't replaced the severed cable yet.
> > * The system idles at between 4-5 watts, which equates to around 35-40
> > cents a month on average for power pricing around here. I have it
> > running all the time and am happy to respond to messages via
> teletype.
> >
> > I will eventually write up more about this on my blog including links to
> > components I bought for the build, but this is pretty detailed already.
> >
> > I will probably also add more current loops, though right now I only own
> > three teleprinters, and one of them I plan to run off of a Nagle board
> > if I can get one.
> >
> > Hopefully this was helpful to give others ideas or at least provides
> > some interesting reading.
> >
> > --Jordan
> >
> > On Thu, Apr 19, 2018 at 11:03 PM, Jordan Spencer Cunningham <js at cunni.co
> > <mailto:js at cunni.co>> wrote:
> >
> > Hi all,
> >
> > Thanks for the encouragement and kind words. Showing the teletypes
> > off at the Maker Faire was a success. John Whitney brought his Model
> > 35 and had it connected to a Linux terminal, and I had my 19
> > printing out SMS and email people sent it whilst my 15 was printing
> > out art the whole day.
> >
> > I have never been to the Maker Faire here in Salt Lake City before,
> > but there were I believe 80-90 total groups showing off various
> > projects of every kind in the State Fairpark Grand Building. I think
> > it's safe to say that the teletypes were one of the more popular
> > exhibits there. I had a pretty good crowd most of the time, and most
> > adults and kids were enthralled with the machines and had a lot of
> > questions. One probably 11 year old girl said she just got a new
> > room, and she said a piece of art I printed out at her request
> > depicting Charle's Shulz' "Lucy" from the Peanuts cartoons would be
> > the perfect thing for her wall. John's machine, which was set up
> > just across the way from mine, seemed to attract a lot of people,
> too.
> >
> > I enjoyed explaining the history of the machines and how they worked
> > electrically and mechanically to people interested in them, which
> > were many. I had a mechanical engineer and an electrical engineer
> > both exclaim that they'd never seen anything so amazingly engineered.
> >
> > There were maybe three or four people who came up with big smiles on
> > their faces and talked about the old days when they or their parents
> > used to work with teleprinter machines back in the 70s. It was fun
> > to see those memories reawakened.
> >
> > A lot of people thought I had retrofitted typewriters. They were
> > excited to hear that the teletypes were completely original designs
> > dating from 1930, operating exactly as they did back then.
> >
> > I was invited to bring the machines to the Thanksgiving Point Maker
> > Faire in September (that's around 20-30 miles south of Salt Lake
> > City), and there were some other groups that wanted me to bring them
> by.
> >
> > It was a fun day and one I'd love repeating again.
> >
> > I was up until 6:00 AM before the faire with a long night of
> > polishing up some finishing touches, printing out extra art to give
> > away, testing, and fixing a couple of bugs in both the software and
> > the machines that I discovered. There was a heart-stopping moment
> > when I thought I had somehow destroyed my last remaining
> > optoisolators on the two boards and thought I'd be completely unable
> > to operate since I couldn't get any replacement components in time.
> > Luckily it turned out to be a really weird hardware bug I have not
> > had time to fully trace that was simply solved by reversing the loop
> > polarity (the boards are supposed to be polarity insensitive and
> > were working fine in the opposite polarity until that moment). I had
> > a few moments like this where I grumbled things like, "Why can't I
> > just be like everyone else and do something easy like play video
> > games?!" However, the end result is well worth the moments of
> > frustration.
> >
> > The machines ran incredibly well and are a monument to how well the
> > last person who owned them took care of them. He became silent key
> > in the 70s, and the machines sat idle in his basement for about 40
> > years until I had them shipped across the country to me last year. I
> > had oiled and greased the major parts, replaced a couple of missing
> > parts, tightened some nuts and bolts, and did some modest cleaning,
> > but there is still plenty I want to do to clean and restore them.
> > Despite that, both machines ran incredibly well for hours and
> > brought enjoyment and wonder to hundreds of visitors.
> >
> > Attached are some photos. I meant to have more, but I forgot to
> > bring my camera. My phone was plugged into the Raspberry Pi to
> > supply the internet connection, so I couldn't take it more than a
> > couple feet away for pictures. Most pictures were taken by my wife.
> >
> >
> >
> >
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>
> --
> Met vriendelijke Groet,
>
> Simon Claessen
> drukknop.nl
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