A2 Plotter

A long time ago, during the ZX Spectrum period, I created a plotter. With this unit it was possible to plot electrical and pneumatic schedules on A3-sized paper. In that time, good printers where quite expensive. To create high quality drawings, I had to build a plotter.

With ZX Spectrum

In that time scanners where out of reach. By adding some electronics I was able to scan black and white, and plot those scans.

In that time the Stepper motor controllers where controlled by a Z80 Pio chip, connected to a ZX Spectrum’s edge connector.

Developing the plotter was a lot of fun in those days.
When I bought a small notebook running MSDOS and Windows 3.11, I created a 16 bits In/ 16 bits Out interface to work via the printer port. The plotter was changed to A2-size and the resolution was changed to 0.1 mm/step

To keep the unit simple I used Direct Drive. The paper axis is directly connected to the motor. The motor uses 200 steps per cycle so I had to create an axle of 6.2xx mm. Well….. almost!

The pen holder is connected to a motor by a line. The biggest problem I encountered was to drive the pen holder without slip of the line. The line is going into the pulley and is locked with screws on the top. The next picture gives an overview.

By changing the pen holder for another, it’s possible to plot with Rotring pens or with coloured felt-tip pens. They are lifted by solenoids pulling a pin upwards. Because of the solenoids, the pen carrier is quite heavy. This is moved by fishing cord. The first problem I encountered was the pen carrier not moving at the first step. Now the fishing cord is doubled.

At first, the software was MSDOS-based and created by me in machine code. It controlled the movement of the motors and the solenoids via an 8 bit PIO, connected to the printer port.

The plan I always had was to control the Plotter by USB. This is the main reason I started with Microchip micro controllers. After a short time I created something that could communicate with a program. This has grown to a real interface.

The software makes it possible to plot out JPG or BMP files as black and white. (see picture above, right).

Some plots

The unit has an initiating possibility to move the paper to 0,0. When initiating, the pen carrier is positioned by running to a micro switch. The paper is controlled by a IR sensor with the paper functioning as reflector.

Ceck the video’s below for some action shots.

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