View Full Version : Electronics help

07-18-2003, 12:52 AM
OK, guys...I need some help. It's time for me to do the electronics side of this project, and it doesn't seem to be working right. Maybe I'm just missing something.

I've tested this board and my motor together (unipolar motor, bipolar mode) and it works just fine...using the on board 555. I need to modify this.

If you'll notice, this board generates its own pulses with a 555 chip. I need to bypass that. (sever the wire feeding the output to the L297?)

I then need to bypass the flip-flop that feeds the direction pin on the L297.

This should be able to be done by severing the output from the 555 (cut the line) and soldering the parallel lines directly on to the chip, right? I'll arrange a more elegant hack later...right now I just want the thing to work.

Anything else that I'm missing... Yeah, one other question. On the parallel cable I'm using pins 2 and 3 for step and direction, as mentioned in the turbocnc.ini file. I'll also need a ground connection -- OK to hook it up to my 5V logic power supply? And, does anything else need to be connected on the parallel port...enable, or busy or one of the other lines?


-- Chuck Knight

07-18-2003, 12:54 AM
I just noticed how bad this scan is...but this is the max allowable size on CNCzone. Maybe if I scanned it in 2 parts...

07-18-2003, 01:06 AM
Nah, 2 parts was harder to understand.

This is the "central" and most relevant part of the schematic. I believe I need to sever the conection betwen pin 3 on the 555, and the step input on pin 18 of the 297 -- and then connect in my parallel port lines. Is ths essentially correct?

I've screwed up, somewhere...my modifications don't work. Thankfully, they're all easily reversible!


-- Chuck Knight

07-18-2003, 09:38 AM
If I was you, I would use some sort of breakout board to interface to your controller board. What I'm thinking is one that has opto-isolation circuit to protect your pc.
Another idea would be to buy a aux parallel board that plugs into your pci slots on the pc just in case your controller throws a fit it won't burn your onboard port messing up your computer.

As far as your electronic mods, from what I see you are basically using logic control at 5v so a wrong move won't be disaster. You may end up with a backwards cw/ccw etc.
I'm short on time to reverse engineer it right now.

Good luck on your mods.

07-18-2003, 10:09 AM

The step and dir pins can be setup in turbocnc, but 2 and 3 will be fine for now.

I would say you need to put the step to #18, dir. to #17 and enable to #16? (hard to see the number). The enable needs to be setup in turbocnc as well, look in the menu under machine setup, misc I/O I think. Step and direction pins are setup under Axis setup.

I hope it works!