Typewriter to Printer: Software Update

I am turning an almost hundred year old typewriter into a Twitter printer.

An update is needed here, since a few things changed, not as much progress as wanted was done though.

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I decided for the future of the project to use a Raspberry Pi to operate the typewriter and the connected webcam.

Why? 

Arduino WiFi Shields are expensive compared to a $10 WiFi USB dongle. Also I can plug in a fairly cheap webcam via USB to the RPi to show images of the actual print job without bothering a network camera. However, I had an RPi around and got the needed python script to read from an API (the typewriter API) and send according signals via a cobbler board going within half an hour.

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Status

The RPi runs a python script that does nothing else than grab a string from an API.

So it basically just gets a string, like “print me this please” and will then according to the characters, send the right signals to the shift registers that control the transistors that will trigger the solenoids. Also it makes a cartridge return and new line when needed based on settings, like every 10 characters.

Advantages

Compared to having the web based print queue push jobs to the typewriter via arduino and probably bother it too much if stuff goes wrong, the RPi python script only asks for jobs if it is okay to do so, but does not have to worry about anything else, other than the paper size.

That also means if I need to reload paper or whatever happens, I just unplug the RPi and fix the typewriter while the online print queue can keep growing.

Also the API will only have jobs in the print queue if the web app decides to put them in there, so it can be from there configureable if hashtags from twitter, or just retweets from one account actually go into the queue.

Therefore there will be an interface to maintain the print queue (auto fill print queue because of name / hashtag, delete tweets, prioritize tweets, easter eggs, etc)

Furthermore, the web based print queue manager can send out tweets/ reminders / emails 5 min before your job is coming into the typewriter so you can watch it happen and after it is done send you the link where to find the screenshot of your print being done.

Considering my last post, I did move on quite a bit: 

  • Tested the shift registers (but new challenge with the raspberry now) need to to it again.
  • Laser cut pieces are wonderful but I got at some point cm and inches mixed up, no biggie, but will do it again some day. The solenoids are not working right now anyway, I switched to fishing string, it has therefore a little play that won’t trigger the key enough to do the trick. I will need to go back to wire when the solenoids are sitting exactly under the keys.
  • Cartridge return I tried a few things now. Some very promising, some just crazy. Undecided what to go for.

Anyway, most of the software got figured out, since I had to step away from the hardware for while to brainstorm again about the hardware.

If you have ideas, let me know. Cheers, michael

 

 

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