I recently wrote about some of the problems I’d had with the Chinese Laser Cutter I bought over eBay. It became apparent that I was going to have to replace the X/Y controller board, as this was not functioning correctly.
The Challenge – adding a new controller
I just pulled my old CNC out of storage, the board is a bi-polar 3 axis driver and parallel port breakout from www.easy-cnc.com.
This differs from the laser controller as it needs to be driven by pulsing the output pins on the parallel port.
I also pulled the gantry out of the laser cutter – unfortunately this has a “Flat Flexible Connector” hooking up the two home sensors and the X stepper motor. It’s going to take some work with a multimeter to figure out the connections.
The motors need 24V, and the controller requires 5V – both of which are available from the laser cutter power supply board.
Since I don’t want to change the connector, and FFC connectors are a bit tricky to find, the first step is figuring out a way of hooking it up…
The motors are bipolar, 4 wire, running at 24V and 0.5amps – I had to create an improvised ribbon cable connector, but it didn’t take too long poking around with a multimeter to work out the hookup.
UPDATE (Sunday) : Earlier today, I tried to discover exactly how the home sensors were wired, but after plotting it out on paper and running a few exploratory tests, I’m going to have to admit defeat. The home sensors are tucked away inside the chassis, and are difficult to access without some major dismantlement.
They obviously work, but according to the wiring I’ve plotted out, 5v and Gnd are actually shorted out across them. Which is not good. Additionally the 5v supply runs at an offset of 120V – I don’t want this anywhere near the parallel port.
A home sensor is most useful when you need to change cutting heads – and this is not something that happens with a laser engraver. So…. the more I thought about it, the more I thought it’s not worth the effort to continue examining them. The X/Y motors work, and that’s the main thing.