[GreenKeys] Teletypes at the Maker Faire

Sat Apr 21 06:30:16 EDT 2018

Thanks for the write up about the "guts" of you display.  Fantastic work!

You mention your blog, can you post the link?  If you have in the past, I missed it.

Steve G./N4TTY
Sent from my iPhone

> On Apr 21, 2018, at 2:52 AM, Jordan Spencer Cunningham <js at cunni.co> 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:
> 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
> 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)
> 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
> 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
> 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.
> Two relays control 120VAC power to each of the teletype motors
> 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.
> 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> 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.
>> 
> 
> <20180420_201740.jpg>
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