Printing Text With A Chart Recorder

A chart recorder printing 'Hello World'

Chart recorders are vintage devices that were used to plot analog values on paper. They’re similar to old seismometers which plot seismic waves from earthquakes. The device has a heated pen which moves across a piece of thermally sensitive paper. This paper is fed through the machine at a specified rate, which gives two dimensions of plotting.

[Marv] ended up getting a couple of discontinued chart recorders and figured out the interface. Five parallel signals control the feed rate of the paper, and an analog voltage controls the pen location. The next logical step was to hook up an Arduino to control the plotter.

However, once the device could plot analog values, [Marv] quickly looked for a new challenge. He wanted to write characters and bitmaps using the device, but this would require non-continuous lines. By adding a solenoid to lift the pen, he built a chart recorder printer.

After the break, check out a video of the chart recorder doing something it was never intended to do. If you happen to have one of these chart recorders, [Marv] included all of the code in his writeup to help you build your own.

6 thoughts on “Printing Text With A Chart Recorder

  1. Clever!

    I suppose it has no backwards gear, so you can only move the paper in one direction. Shame, cos otherwise you might be able to rig it as a plotter. I dunno if anyone actually still uses those, but they were very big back in the day. If it could drive backwards, it’d just be a matter of writing a driver for it, and he could do tiny CAD printouts.

    Actually we had a plotter at school, for technology lessons, drawing schematics mostly. That was 20-something years ago. Tho before cheap inkjets and lasers, so maybe that’s why.

    From reading the article, seems like he’s already thought of it, and the mechanics of it won’t allow the paper to go backwards easily. My other idea was, instead of lifting the pen, just turn off the heat. But that takes too long, apparently. Maybe a peltier device for the heater? If you could squeeze in a peltier, they should be able to suck and push heat fast enough to overcome the thermal mass of the drawing needle. Then again, maybe the solenoid he’s used is the best way.

    1. I think Robert Redford was giving them away for a while. I’m not sure but you should look into it. I definitely remember him talking about ‘free peltier’ a few years back.

      Seriously though I have an old marine depth finder head unit with a built in chart recorder that’s been in the some day pile for a few years. I may have to see about it.

      1. Nah, you’re thinking of something different. Robert Redford is trying to free a man who’s in prison for overclocking people’s computers. And now he’s spending some time in the cooler, ho ho ho!

    2. Yeah, it takes at least half a minute to cool down and to warm up. I think faster than with the relays it just isn’t possible by switching the heat on and off. The only thing that could be faster I can think of is using a laser to write on the thermopaper… but that’s something entirely different ;)

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