Introduction

A printer prints in lines of dots, but a plotter draws — with a pen, like a person: pen down, draw a line, pen up, move to the next one. In the 80s Apple computers had a colour plotter with a turret head for four pens: the computer named a colour, the head turned, and the right pen came to the paper. In this kit you build such a plotter next to the Apple ][ of the simulator — the mechanics, the panel, the turret and a card in a slot — and run a program on it with a menu of seven pictures.

  • lesson 1 — the plotter and the panel: two axes with stepper motors, a pen, arrows and PEN UP/DOWN;
  • lesson 2 — the turret: four pens on a turntable, SELECT, turning to the right pen and the BUSY lamp;
  • lesson 3 — the card in the slot: addresses $C090…$C092, registers, reading the limit switches, the REMOTE/LOCAL switch;
  • lesson 4 — a program with a menu on a disk: a house, a rainbow, a flower, a star, a spiral, a word and a spirograph.
Apple ][programslot 1 card$C090 · $C091 · $C092panelarrows · PEN · SELECTCD4019REMOTE / LOCALX and Y axesSTEP · DIRpenPENturretcolour → turnlimit switches L0 L1 and BUSY — back to the computer ($C091)
How the plotter is built: the computer writes three addresses to the card, the CD4019 picks who drives the motors and the pen — the computer or the panel. The card hands the limit switches and BUSY back for reading.

What you need

The computer is the Apple ][ built into the simulator: the DEMO button. The plotter goes onto the same canvas and in lesson 3 connects to its bus.

The chips are ready-made: the kit file plotter-chips.json, imported into the library with one button. These are real Texas Instruments CMOS 4000 chips — CD4013, CD4017, CD4019, CD4070 and others — with the same pin names as in the datasheet. Here we don’t build them but use them: labels on the pins, double-click a pin.

The mechanics come from the Mechanics button: two linear axes, a turntable, four pens and paper. The panel is ordinary buttons, clocks, a switch and LEDs from the palette.

The program is on the disk PLOTTER4.dsk: it goes into the machine’s disk drive with the ⬆ button.

How much it is

The whole plotter is 26 chips with 1,490 transistors inside. Plus the computer it is connected to.

Mode

Build and check in Turbo mode: there the Apple processor runs at its real speed and the plotter card is computed along with it. The panel clock (60 Hz) and the turret clock (10 Hz) run in real time.