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Topic: Electronic typewriters (Read 915 times) previous topic - next topic

Johan_Ha

I've bought two typewriters from a flee market. I thought of turning them into plotters. The first one had a stepper motor for the horizontal movements, but it feels the steps of the motor makes a rather big step, probably a half character step. And the cylinder also moves in large steps, probably with a solenoid. I might end up just disassembling it picking away motors and solenoids. It costed 1 €.

Then I found a 5 € Brother typewriter. Its cylinder moves very smoothly with small steps, maybe 10 steps per line height. Clearly a stepper motor, not a solenoid. And the horizontal movement is some 7-8 steps per character width. This typewriter will be my plotter project! Either I just use the original stepper drivers or I connect new drivers and spare me from the tedious task of figuring out pins and voltages and whatnot. The pen will probably be a thick-ish felt tip pen attached to the typewriter carriage. The solenoid that stroke the type wheel might do the pen down action if I can lower its force somehow.
____________________
- One day my stepper motor driver works like a charm. No task is too big for it and I can do anything with it. Next day it refuses to work and even the tiniest motor blows its fuse. What's wrong with it?
- It's bipolar.

Paul_KD7HB

Way back in the early 1980's, I was a communications consultant for a small company that put mini-computers in banks to do their processing. I looked at the Brothers typewriters to print output from computer terminals. A company produced a kit to add a serial interface to the typewriter. Worked very well. All the paper and print head movements were controllable, just as you found.

I have no clue if there is any documentation on-line for the interface.

Paul

Johan_Ha

That's good to know, Paul. I haven't opened the machines yet, so I don't know what stepper motors they have and whether I can use their drivers.
But what I found was that the first typewriter indeed had a stepper motor for the cylinder, too. It has a conical clutch thing, engaged by a solenoid. I'll probably glue the clutch and reuse the solenoid for something else. The vertical resolution of the revolving cylinder is about 70 steps per inch. Much smaller steps than I first measured.
But the horizontal steps of the typewheel carriage might be too large. Perhaps micro stepping can compensate.
____________________
- One day my stepper motor driver works like a charm. No task is too big for it and I can do anything with it. Next day it refuses to work and even the tiniest motor blows its fuse. What's wrong with it?
- It's bipolar.

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