Pens for Atari, CBM and TRS plotters (was: atari

[Tony Duell]

> One solution might be to obtain the ink and pen from a strip recorder and
> fit it to the plotter.  These don't dry out as quickly and can be easily
> unclogged with a small cleaning wire.

These plotters have a plastic cylinder on the carriage with 4 pens fitted 
round it (it's a bit like the chambers of a revolver gun). When the 
carriage moves to the extreme left, a spring bit of metal on the frame 
hits a ratchet tooth on the cyclinder. By moving the carriage to/from the 
left side 3 times (I think), the cylinder is turned by quarter of a turn, 
thus sleecting the next pen.

Theres a magent embedded in the cylinder and a reed switch on the 
chassis, used to detect the home position of the cylinder (black pen in 
use, if you've fitted the pens conventionally). 

The points of the pens fit into a spring metal circle with 4 holes that 
keeps them off the paper. Across the printer, just behind the carriage, 
is a rail operated by a solenoid at one side of the chassis. When 
operated, it pushes the selected pen forwards, into contact with the paper.


Because of this consruction, it's almost impossible to kludge in some 
non-stnadard pen.

-tony