Post
by stevep » Mon 14 Apr , 2008 22:38 pm
Well, I got a chance to open the Orac up this week, and did a sketch of the wiring before starting to take bits out. I was a bit confused at first at the wiring of the emergency stop switch and what I thought were homing switches- seems a bit odd that these are connected together, and to the main power relay, when you're not familiar with the concept. Once I did a bit of research on this forum, however, I realised that they were limit switches, and it started to make sense. I bought a breakout board from CNC4PC, with charge pump and analogue out included, and I want the machines to be self-contained (my workshop gets dusty and would kill an exposed normal PC quite quickly I think,) so I bought two small form-factor 3Ghz IBM PCs for 80 quid off ebay to fit inside the machine cases. I also splashed out a bit and bought two industrial 15 inch touch screens, also off ebay. I managed to get all the bits mounted inside, and some of the wiring done, in a couple of afternoons. I made a new end plate for the rack with a slot for the parallel port connection, and fitted an aluminium shelf inside with the breakout board mounted on top, and space for a couple of boards below (for when I get round to the ATC.)
One question- is there a normal way to connect the emergency stop? I'm a bit confused as to whether to just hook it to a pin to send a signal to mach3, or if it's better to make it kill the power to the spindle too. I guess it's better to allow mach to stop the spindle and drives in a controlled fashion, but I'm a bit unsure as to how to combine the charge pump, the output enable pin, and the emergency stop button. If anyone has any tips, I'd be grateful.
I've attached some pictures..
Oh, and I noticed some posts on the forum regarding converting the 5v of the breakout board to the 12v of the drives. It seems to me, however, that the inputs of the drives are pulled high internally, so they require pulling to ground, which means it's not really a voltage shift, you just need the input to go low. I decided to try using a ULN2803 chip that I've used many times in the past, since all the series resistors etc are all contained within, so all you have to do it connect the input to one side, and the output to the other. And there are 8 drivers in there, all capable of sinking 500mA each. I'll let you know how I get on with it, since it's a lot easier than using individual resistors and transistors, especially if your soldering leaves a bit to be desired...
-
Attachments
-
- rack.JPG (84.95 KiB) Viewed 26450 times
-
- layout.JPG (89.74 KiB) Viewed 26450 times
-
- internal pc.JPG (117.22 KiB) Viewed 26450 times
-
- board mounting.JPG (112.98 KiB) Viewed 26450 times
