Hi this is larry again thanks for the input. Yes I just whant it to pause the mach program when I push the estop button.  Also I know there will be some los of steps even a hundred steps is okay. What i will be able to do is reset the cutter at the home position and then tell the program to start from here or the next line and the machine should go to where that line is on the machine. Thenit will start the cut a few steps before it was stoped for what ever reason. I have had the machine lose 4 or 40 steps and ruin the work before I could run to the computer to stop it. It could have been save but I had no choice but to start over because I didnt know where the steps were. My board has a wire between to terminals and when it is unhooked or disconnected the board losses power. It is a  ( pc4cnc board ) What I realy need to know is if I have a pulse sent back into the computer will it tell the pause button to pause the machine . And howwould I do that  thanks for the help so far...

FeedHold will NOT stop the machine instantly, only STOP will do that.  FeedHold will often continue running for several seconds after you press the button.  If you're OK with losing steps (and you really have no choice....) your best bet is a hardware switch that disables the drives directly, without involving Mach3, and a separate input to Mach to issue a FeedHold.  You will have to manually figure out where to restart from in any case, because you cant simply restart from any line of the program.  RunFromHere is *supposed* to let you do that, but there are frequent reports that it is not very reliable.  Usually, it's best to back up to some previous rapid move, and manually ensure that coolant/spindle/whatever are in the correct state before re-starting the program.

Regards,
Ray L.

BTW - If you have servos, hitting Stop will not generally cause lost steps.  With steppers, it pretty much always will, unless the machine is moving very slowly.

Regards,
Ray L.

Larry,

It seems you have one of our breakout boards. All our breakout boards have a terminal called EN, which require a +5vdc signal in order to enable outputs. We recommend you connect the e-stop signal in parallel with this terminal.  So if you use a NC switch for e-stop, when you press it and interrupt the signal, you will make the controller aware of the e-stop situation and disable the outputs at the same time. The idea is that it is not the PC based controller the one taking the action of stopping the system. Maybe this wiring diagram illustrates it better: http://cnc4pc.com/Tech_Docs/E_STOP_N_EN_Wiring.pdf.

We do not recommend taking power off the breakout board or any other logic in your setup on e-stop, as this could allow noise to get in and cause unpredictable actions.

I agree with Ray that if using servos, and keeping the driver and encoders powered all the time, using e-stop just to disable the drivers, the lost steps could be minimal, just the pulses sent to the driver between the time the breakout board outputs were disabled and controller stopped sending pulses. If you wire it this way, you must really know what you are doing, as when the drivers are enabled back again and if they moved, they could cause a violent motion.  I never had this case, but always imagine it could be very dangerous.

Arturo Duncan
http://cnc4pc.com

Thanks guys I realy apreciated the help. I was reading the instructions on the bob this morning and it said that the estop will cut power to the motors when activated. It uses normaly closed and when you push the button it opens the switch making it go low. It also said when estop was pushed it would send a signal back to mach 3 or control software informing it of the action. I dont know how but I guess all I realy need to know is how it works (or I mean that it does work???) I have never hooked up the estop as I was afraid it would do somthing stupid like destoy my program or somthing along that line. I will be hooking it up within the next few days. Keep our fingers crossed.  HA HA

Yes Duncan that is the board I think I bought it from you if that is your web site.  I just reread th instructions this morning. I had to go out to the shop and get it out of my other computer. I will hook it up as said with a nother switch as said to turn of the board until ready to reacivate it. I think I will be needing the relay board in  the near future so I will probly be getting ahold of you  I want to start the spindle and vacum with the board as well. So that when I push estop they will all stop as well as startin them with the program when I am ready to cut not 2 or 3 minutes befor,