Plasma table 2m x 1m

[Lee Roberts]

Amen to that !

[Robin Hewitt]

Bit of a delay designing the circuitry. Decided the best place for the CPU was at the cutting head. Close connects for the Y and Z axis controls and switches. Reasonably close connects for the X axis stepper controls and end stop.

Decided to use fibre optic links for the computer connection so I don't have to worrry about interference from the torch.

The Z axis is screw driven by a zippy 24 volt DC motor with brake and 4 bit control on the speed.

The motor has a chopper disc to show where it is.. Rather than waste cpu time oversampling to read the chopper I decided to put it on an interrupt. Here's my cicuit. If either chopper optic changes the the cpu interrupt goes low until I read the data on the input pins.

I'll let you know if it works

[Robin Hewitt]

Circuits done, pcb's made, thought I'd start with the fibre optic link because I've never done one of those before :D

Set up a full duplex terminal so anything I typed on the keyboard had to go out around 5 metres of cable as light before it showed on the screen. Worked a treat.

That's a letter 'i' on the 'scope, on it's way back from the optic at 9600 baud. Can't ask for cleaner than that.

Now I know I can upload programs for testin', next comes some steppin' :D