More like this, please.

Seconded. We want more Boffins-in-Sheds articles.

From 91-97 I worked as a draftsman on autocad and watching a pen plottter in full flight was both terrifying and fascinating at the same time.

The company I worked for didn’t have a pen plotter so we had to go to a print shop if we needed large copies, but they replaced it with a calcomp a0 inkjet which was an open carriage. Used to often go to the room the printer was in after setting it going and someone would be standing there mesmerised by the fact you could see the ink being laid down on every pass.

I was always fascinated by watching big x-y plotters working on drawing circuit diagrams... they never seemed to do anything in a logical manner, just do a little bit here, then lift the pen and wander off to another corner apparently unconnected.

Amazing things!

Years ago I worked at a government site where we had a pen plotter and it got a good workout when it had to print a specific Powerpoint slide. I kid you not, this was in the days that you could get Powerpoint to work on an A0 format slide with so much detail that the fonts on it were 10 point size - I wouldn't dare doing that now as Powerpoint would probably nuke not just the slide but the OS with it.

What was fun was to see the paper fly back and forth so fast that it had no time to fall down, but the whole thing took over 35 minutes to be drawn with the pens, and given the popularity of this specific slide it had to be plotted a *lot*. So, in the end they got an inkjet plotter which wasn't as much fun but which "spat"* out that A0 in a far shorter time (10min or so).

I personally like mechanical plotters and I was very sad I had to get rid of my Roland A3 plotter when I moved to a smaller place.

* comparitively

Not the plotters problem - it just does what its told. The plotting software has to be smart enough to sort these things out. Early PCs were barely fast enough of reliable enough to do the relatively simple calculations but I worked in a chip design place and we had software that would pretty much minimise the plotting time - alas the pens just ran out without the software having any knowledge so you have to watch them - and be able to hear a pen running out or hours would be lost. I had a chip with 4 thousand transistors on it that a pen would run out two or three minuted before the end of a 6 hour plot so I had to work out how to drive the damn thing so I could change the pen before it ran out. Learned a whole lot of programming and stuff and then someone pointed out I should just wait till the pen had done about half its work.Bastard!

I spent some happy time a million years ago writing a program which read in an HPGL file, converted all pen movements to absolute and then reordered to use the six pens sequentially. Hugely sped up a lot of plots, because changing pens is slow.

Also ... Daniele Procida. Haven't seen that name since Usenet, about thirty years ago.

Back in the dim and distant past I worked with both HP A3 pen plotters and the big Calcomp A0 ones, down to the level in some cases of writing drivers for them. They were always more fun than the later large format inkjet printers but were a lot slower and a lot less reliable!

We even modified one of the HP plotters to draw etch resist onto PCBs, basically by butchering a plotter pen into a holder for a PCB pen. It worked better than we expected.

We used to sell the Penman Plotter (It was designed and made in Worthing by part of Eurotherm where our shop was)

It was aTurtle Plotter relying on dead reckoning so any wheel slip ruined a plot, the one advantage was as it it had quite a long tether so could do quite large plots.

https://www.youtube.com/watch?v=Zt0qeGYjzxw

My first foray into "Field Engineering" led me to spend several years as a Flying Tool Bag and Tech Support person with CalComp when it was still a leading force in x,y plotters and microfiche printers. That was when they had just absorbed "Century Data", the Storage Device thorn in IBM's side.

Ah, the memories . . . of all sorts,.

Would be great if there was any prospect of anybody having an Pi Zero in stock any time soon. Or indeed at all.

My university project was to hook up a BBC mico to a small plotter. Not to draw anything, but modify the carriage to hold a scanner instead of a pen. So I could pull in an image of an etched PCB, then scan it for the tracks and pads. Swapping the scanner for a small electric drill meant that I could then make the component holes. Had to use assembler to get the code fast and small enough. The only large chunk of memory I had to store the image was to use the video frame buffer, but did so in such a way that the PCB image, and the hole searching algorithm was displayed in 4 colour mode on the screen.

My first non-trivial hardware project that was more than just flashing an LED or reading a switch status, was the opposite of this plotter. I had a dual 8-bit A/D converter and a couple of potentiometers in the same arrangement as this plotter built as a rudimentary "point" digitiser. It ran on a Video Genie, programmed in BASIC initially and had to some trig to calculate where the pointer was. It had to be calibrated on every use and each reading took a perceptible time because BASIC andbecause the resistance of the Carbon track pots would vary based on room temperature. I'd not really thought about much and was a little puzzled by the changes in position so left it on over night reading and recording the "home" position every 5 minutes, had a look in the morning and realised the reading was changing slowly overnight as the house cooled down then warmed up again in the morning :-) Accuracy wasn't a huge issue considering the "graphics" resolution ion screen was 128x64 :-) I did re-write it in Z80 and called the ROM BASIC trig functions, which was a bit faster. On reflection, considering the accuracy, pre-calced look-up tables would have been better.

Later, I built a small (A5-ish) flatbed plotter from old stepper motors and some long threaded rods controlled by a BBC Micro. That was fun and actually very, very accurate. It never got upgraded to self-controlled pen selection though. Suitable pens basically meant buying proper plotter pens though. Most normal pens either didn't flow the ink well enough or the nibs (eg felt tip pens) were too large. Fun times.