Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: larryc on December 01, 2009, 09:05:04 PM

Title: how to hook up a e stop
Post by: larryc on December 01, 2009, 09:05:04 PM
Hi this is larry . I have hardly ever asked a Question before . The program is so easy to use as soon as you get it going . But I need to ask one question now. I have whent over some of your post but there is so many of them. I need to know how to hook up my estop so that when I push it it will tell  mach to stop the g code. I now have it hooked to my  cnc interface board. I think it is a 10 cnc for cnc board. Any way all it does is stop the board from runing. What I need to know is there a way to signal the computer. I have had to stop the machine a few times and then run over to the key board and tell it to stop. Then go set the machine and spend the next 2 hours reseting the mahine then the computer. That is if I am lucky. I would really apreciate your help thanks
Title: Re: how to hook up a e stop
Post by: Hood on December 02, 2009, 03:35:08 AM
I am not sure how the E-Stop input to the breakout board  you have works. Normally however you would have a double pole normally closed E-Stop, one pole would cut the power to your drives (via a contactor) and the other pole would be input to Mach on the E-Stop input.
 It should be noted that when you press the E-Stop (or Stop in Mach) that you will most likely have lost position so a rehome will be needed.
Hood
Title: Re: how to hook up a e stop
Post by: olf20 on December 02, 2009, 07:03:08 AM
Are you wanting to just pause the program???
If so the FEED HOLD will do just that. When you want to restart
the program, just click on the CYCLE START button.

olf20 / Bob
Title: Re: how to hook up a e stop
Post by: larryc on December 02, 2009, 11:57:07 PM
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...
Title: Re: how to hook up a e stop
Post by: larryc on December 03, 2009, 12:10:05 AM
hi this is larry again I didnt tell you what I was using it is a 4x8 gantry router for cutting wood. I have gecko drives and using steppers with a 8 to 1 gear reduction. I mostly am doing toys, signs, and photo typing for my own use. I use aspire 2 and bobcad.
Title: Re: how to hook up a e stop
Post by: Hood on December 03, 2009, 03:04:54 AM
Ok, there are two different things here, FeedHold and E-Stop.
FeedHold will stop your machine in a controlled manner and you will not lose position.
E-Stop is for emergency use, it will stop immediately but you will lose position.

You could have either or both from external buttons but I would say a properly configured E-Stop is a must on any machine.
The way most Breakout Boards, I have seen, work is you can have an E-Stop button connected and when that contact is broken the BOB will stop putting out pulses and at the same time will inform Mach of the E-Stop condition, which will put Mach into Reset.

 I have no experience with your BOB so I am not sure if this is the case with it, I will try and have a look later in the day.
Hood
Title: Re: how to hook up a e stop
Post by: larryc on December 03, 2009, 09:53:39 AM
yes when I hit the stop button on mach 3 the program does stop without loosing steps, But I had a bit come loose a couple of month ago and the bikt started to dig into the board I was cutting.  By the time I got to the mouse and stopped mach the bit was 1 1/4 inches into the board. I reset the bit and spent 2 hours reseting the program. It when 100 or so steps beyound where it was. the bit stoped moving but the machine thought it was still going. Talk about missed steps.... I only need somthing that is fast for example I could have a button in my hand so that when I push it the machine will stop dead.and also stop the mach 3 program then when I reset the mach program it woul continue. Hope you know what I mean.
Title: Re: how to hook up a e stop
Post by: Hood on December 03, 2009, 06:27:32 PM
You can't do that, when you press Stop or use an external E-Stop you will lose steps if an axis is in motion unless it was moving very slowly but even then it is likely you will have lost. Maybe I should say you will lose position rather than lose steps as Mach will cut the pulses but the axis is unlikely to be able to stop dead without some motion due to momentum. 
 When you do an E-Stop you should re-home your machine so that Mach again knows where the axis actually are.

What you want to do is have a double pole E-Stop switch, use one pole to cut the power to the BOB as you have and the other pole should go to an input on the BOB and you configure that as the E-Stop in ports and pins. Then when you hit the E-Stop button, the BOB will stop putting pulses out but it will also send an E-Stop signal to Mach and it will stop instantly as well. You can then re-home your machine, back up a few lines of code and do a Run From Here.

Hood
Title: Re: how to hook up a e stop
Post by: rrc1962 on December 03, 2009, 08:57:23 PM
An E-Stop is for an emergency when things go very wrong and you need to stop it in a hurry.  It should be a big red button always within reach of the operator.  If you have to hit the E-Stop you can pretty much count on what ever is on the table to be scrap.  Just rehome, figure out what went wrong, fix it, load another blank and have another go at it. 
Title: Re: how to hook up a e stop
Post by: larryc on December 03, 2009, 10:23:05 PM
Hi yes hood that is what I want to do thanks.I just wanted to go back a few steps and then home the machine to 0 X O y Oz . Then let the machine go back to where ever it was.  then start cutting from there. I like to keep things simple. Less to remember. I am not as Quick to remember thing now days as I use to a few years ago. Thanks again. The program is easy to use and easy to set up. But somtimes it is easier to just ask how to do somthing from someone who has done it or who knows. Thanks
Title: Re: how to hook up a e stop
Post by: HimyKabibble on December 03, 2009, 10:25:57 PM
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.
Title: Re: how to hook up a e stop
Post by: HimyKabibble on December 03, 2009, 10:28:56 PM
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.
Title: Re: how to hook up a e stop
Post by: arturod on December 04, 2009, 10:25:21 AM
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
Title: Re: how to hook up a e stop
Post by: larryc on December 04, 2009, 10:26:33 AM
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
Title: Re: how to hook up a e stop
Post by: larryc on December 04, 2009, 10:37:58 AM
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,