3 ms·

I'm reasonably certain that Model 15 is older than 15 years, as they stopped making them in 1963, and the bulk of the production was earlier. Also as an aside

by Aloha 12y ago

I'm reasonably certain that Model 15 is older than 15 years, as they stopped making them in 1963, and the bulk of the production was earlier. Also as an aside - if you were using a model 33 or 37, you could use it with a simple RS232 to current loop converter, and agetty on a linux boxen - then you could use it as a log in device too, rather than just a serial/console printer :-D The other thing I don't get is why use the optoisolator relay setup, the voltages involved are low enough that a normal 5v/250v relay would be sufficient - perhaps the current draw is too high for the raspi to handle?

Animats 12y ago
The Model 15 came out in 1930, and was produced through 1962 or so. Much of the production was during WWII. It's hard to tell when a machine was made. The motor, typing unit, keyboard, and base are all very easily removed and interchanged. It was normal Bell System, Western Union, and U.S. Army practice to swap those in the field and send them back to a depot for cleaning and repair, so the components may be from different periods. Rubber pressure rollers under the platen indicate a post-WWII machine - earlier machines used wood, because oil-resistant synthetic rubber wasn't available in 1930. Most relays aren't fast enough to handle the 45 baud data rate. The relays that are tend to have small contacts, and thus arcing and contact burn problems with the inductive kick from the selector magnets. The Omron G3VM-401B is a good solid-state opto-isolated relay for the job; it can handle 400V, and costs about $2.50.
cnvogel 12y ago
> The other thing I don't get is why use the optoisolator relay setup The article uses the optoisolators and relay drivers, not the relay itself (for the serial data). And as shown in the article linked, it's not setup to be galvanically isolated. Given that the TTY has larger coils and motors, and might also be grounded to some other machinery (e.g. the mains protective earth), I can see why one would want to break the groundloop to the Arduino or serial/USB connector on a PC. The relay modules seem to have one control input wired: Vcc, In1, In2, GND. And a separate jumper for Vcc and Vcc-JD (as seen on a datasheet I found on the web for the 4ch version). http://www.sainsmart.com/arduino-compatibles-1/relay/4-channel-5v-relay-module-for-pic-arm-avr-dsp-arduino-msp430-ttl-logic.html http://www.sainsmart.com/arduino-compatibles-1/relay/4-chann... If you'd open the Vcc-JD-VCC jumper, have a 5V supply at JD-VCC and GND, supply 3.3V from your arduino to Vcc and connect In1/In2 to your GPIO/serial TX, then you could have your TTY and Arduino potentials completely separate.

by Aloha 12y ago

Animats 12y ago

The Model 15 came out in 1930, and was produced through 1962 or so. Much of the production was during WWII. It's hard to tell when a machine was made. The motor, typing unit, keyboard, and base are all very easily removed and interchanged. It was normal Bell System, Western Union, and U.S. Army practice to swap those in the field and send them back to a depot for cleaning and repair, so the components may be from different periods. Rubber pressure rollers under the platen indicate a post-WWII machine - earlier machines used wood, because oil-resistant synthetic rubber wasn't available in 1930. Most relays aren't fast enough to handle the 45 baud data rate. The relays that are tend to have small contacts, and thus arcing and contact burn problems with the inductive kick from the selector magnets. The Omron G3VM-401B is a good solid-state opto-isolated relay for the job; it can handle 400V, and costs about $2.50.

cnvogel 12y ago

> The other thing I don't get is why use the optoisolator relay setup The article uses the optoisolators and relay drivers, not the relay itself (for the serial data). And as shown in the article linked, it's not setup to be galvanically isolated. Given that the TTY has larger coils and motors, and might also be grounded to some other machinery (e.g. the mains protective earth), I can see why one would want to break the groundloop to the Arduino or serial/USB connector on a PC. The relay modules seem to have one control input wired: Vcc, In1, In2, GND. And a separate jumper for Vcc and Vcc-JD (as seen on a datasheet I found on the web for the 4ch version). http://www.sainsmart.com/arduino-compatibles-1/relay/4-channel-5v-relay-module-for-pic-arm-avr-dsp-arduino-msp430-ttl-logic.html http://www.sainsmart.com/arduino-compatibles-1/relay/4-chann... If you'd open the Vcc-JD-VCC jumper, have a 5V supply at JD-VCC and GND, supply 3.3V from your arduino to Vcc and connect In1/In2 to your GPIO/serial TX, then you could have your TTY and Arduino potentials completely separate.