E-Stop switch and BOB Enable PIN question.

Hello all,

I hope I am in the correct forum. I am looking for some advice and I know you guys can help get me going here. Over the last several months I have been building a CNC Gantry Router that I have documented to maybe help others here .

I have reached the point that I need to start doing some more of the wiring. In particular the E-Stop and the enable on my Break Out Board.

Currently, I am using a CNC4PC break out board. It is the C10 model. At this time I am only using pins 2-9 on the outputs to drive my stepper motor drivers.

The breakout board has an enable pin that looks for a 5V signal to enable the boards tri-state buffers. Right now I have this hard wired to the 5V supply to enable the buffers so I can send the signals to the CW230 drivers that I am using.

Here is what I would like to accomplish.

I would like LinuxCNC to use an output pin on the breakout board to drive the enable pin on the board when the power is applied in the AXIS GUI. I would also like the E-Stop to disable the enable pin on the breakout board when it has been activated in the GUI or the mechanical E-Stop swith.

To do this I think I need to assign an input pin on my BOB to the E-Stop switch and an output pin on the BOB that will loop back and drive the enable circuit on the BOB. But how do I AND the power switch in the AXIS GUI to this? Here is what I see in my head:

This should give me the following:

If Either the E-Stop switch OR the AXIS E-Stop go HIGH then the E-Stop input to the AND should go low.

If the E-Stop switch input to the And gate is HIGH (Indicating that neither have been pressed) AND the AXIS Power is HIGH, then I will have the output pin HIGH enabling the ENABLE input on the BOB.

Now, I know that I will need to create a couple of signals, an Input signal on the BOB representing the E-Stop, and an Output Signal on the BOB to represent the enable. Maybe something like the following?

net estop-external-switch <= parport.0.pin-xx-in
net BOB-enable => parport.0.pin.yy-out

Where xx and yy represent the pin that will be assigned to them.

How do I glue the rest of the stuff together? Do I need to load a Hal component for the NOR and AND gate and wire them up in HAL?

Sorry for the long post, I just want to make sure I understand enough to proceed and to document it well enough that another newbie can follow along.

Thanks so very much for your time and patience with me.

Joe

I think I had a brain fart!

I cannot use the BOB to enable or disable itself, If it is diabled, I cannot get an output pin on the card to change states to re-enable it.

Hmmm... Any ideas on how I can get this functionality? Whould using just the external E-Stop be enough? What I want to avoid is the random signals that are being sent to the parallel port while the computer is being booted up and the power is applied to the drivers. My el cheapo drivers do not have an enable or pump.

I wonder if it would be safe to install a small solid state relay on the power supply to the drivers, then use a signal to turn them on or off?

I am up for ideas folks!

Thanks again and sorry about the confusion.

Joe

OK,

I think I have muddled a solution. I have previously purchased 2 of these relay boards from cnc4pc to control the router and vacuum. (I have since purchased a SuperPID for the router) These are rated at 10 Amps. I have 2, 36V power supplies that are rated 6.5A on the AC input. What if I used these in conjuction with the above post to turn the stepper motor drivers on or off based on AXIS power and estop and the external estop?

Sound like that would be a good solution?

Joe

OK, maybe I am sounding like a sound board, but I just realized that if I use the estop to control the power to the motors, I could run into a problem.

Say I am rapiding a long distance at a couple hundred IPM and I hit the estop. Power will be removed from the motors and the drive train will coast won't it? where if the power remains but LinuxCNC stops sending steps, the holding torwue will stop the motors faster wouldn't it?

Or does it matter, will it stop fast enough? My machine rapids at 210 IPM. Not fast by comparison to some machines. It is driven with ACME 1/2-10 5 start screws with two antibacklash nuts on each screw.

Thoughts folks?

Joe

Acme screws don't really back drive. (coast). Combined with steppers will stop pretty darn quickly.

Thanks Todd for the feedback. So you think I would be fine combining the software power and estop with a physical estop as outlined above would be safe enough? If that is concensus, then i will be happy to do it that way. I have a couple of teenage sons that like to help, and I just want to make sure they have a reasonable safety margin when they operate the machine. (Doesn't fix stupid, but at least mitigate what I can)

Regards,

Joe