Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: Duc748 on November 10, 2010, 04:55:11 PM

Title: E Stop
Post by: Duc748 on November 10, 2010, 04:55:11 PM
Hi All,
Personally I prefer a mains voltage control circuit for the E Stop rather than software controlled by mach3.(software crash no E stop)
Just wondering is it possible for some way of telling mach that a E stop of this configuration has been pressed so as mach would stop running too?

Rick
Title: Re: E Stop
Post by: Hood on November 10, 2010, 05:15:38 PM
I have that on all my machines (24v in my case) for the E-Stop string to contactors etc  My E-Stop switch however is double pole so I have one pole  for the 24v side and the other for the 5v to Mach.
If you have just a single pole E-STOP switch you could easily put a relay in the E-Stop string and have the contacts signal with 5v to Mach.
Hood
Title: Re: E Stop
Post by: Duc748 on November 10, 2010, 05:38:50 PM
Thanks hood for your advice.
My E Stop is a single pole and is the control circuit for the latching in on the contactor, I dont quite understand about the 5v signal you refer to..does this go open circuit with the e stop?? also is the 5v an input to mach?

Rick
Title: Re: E Stop
Post by: Hood on November 10, 2010, 05:43:55 PM
As your E-Stop is just a single pole you could put a relay, with a coil of the same voltage as your E-Stop string, in series with the switch. That way the coil would be energised thus closing the relays contacts. The contacts of the relay would have the 5v signal to Mach, how exactly would depend on whether you have a breakout board (and which one)  or just connect direct to the parallel port.

Hood
Title: Re: E Stop
Post by: Duc748 on November 10, 2010, 05:54:28 PM
The contactor Im using is 3 pole and each pole is electrically isolated from each other...could I use one of those poles for the 5v instead of a relay??..or am I going of track here?
The breakout board is just a basic standard one.

Rick
Title: Re: E Stop
Post by: Hood on November 10, 2010, 06:03:48 PM
You could but you would have to be careful that you dont pick up noise from the higher voltages on the other contacts especially so as your breakout board is not optically isolated.
Hood
Title: Re: E Stop
Post by: Duc748 on November 10, 2010, 06:09:57 PM
So a optically isolated bob would eliminate the electrical noise?
also is the 5v taken from the parallel port and fed back as an input to mach, or would I need a 5v power supply? The 5v is the part im unsure of.

Rick
Title: Re: E Stop
Post by: Hood on November 10, 2010, 06:18:21 PM
The optical isolation would help more if you got any high voltage/currents on the wires as it should protect your port and pc from damage, then again PCs are probably that cheap now that its maybe not a huge concern.

Ok the 5v side of things would just work like any other input you have on your BOB, for example how are your limits wired, do they just come from the input, through the switch to the bobs gnd?

Hood
Title: Re: E Stop
Post by: Duc748 on November 10, 2010, 06:29:40 PM
Yes my limits are wired as you  pointed out..The way you have explained has now made it very clear for me to understand.
Thanks again Hood  (what would we do without the knowledge from people like you?)

Rick
Title: Re: E Stop
Post by: Hood on November 10, 2010, 06:44:31 PM
Forgot to say best to use shielded cable to minimise the potential of picking up noise.

Hood
Title: Re: E Stop
Post by: Duc748 on November 10, 2010, 07:02:56 PM
OK cheers..

You dont fancy setting up my machine do you? ;)

Rick
Title: Re: E Stop
Post by: Hood on November 10, 2010, 07:07:04 PM
No problem, bring it along to my workshop at the weekend ;)
Hood
Title: Re: E Stop
Post by: rrc1962 on November 11, 2010, 09:33:01 AM
You could also do it without a relay using a DPDT estop button. Use one side to disable the drives and use the other side, wired NC, as an input to Mach.  Set the input as active high and when the button is pushed and the switch opens, mach triggers an estop, while at the same time your drives shut down.  I agree with Hood in that high voltage relays are better in a noisy environment.  Never had noise issues though, even running HF plasma.

I started using the G540 drives and this functionality is built into the drive.  When I disable the drive with an external estop, it sends an estop request to mach.  I think that is built into their internal BOB.
Title: Re: E Stop
Post by: Bob La Londe on November 11, 2010, 11:20:16 AM
Use a double pole double throw switch.  Cut AC to machine with one, and cut e-stop circuit to LPT port with other. 

Hi All,
Personally I prefer a mains voltage control circuit for the E Stop rather than software controlled by mach3.(software crash no E stop)
Just wondering is it possible for some way of telling mach that a E stop of this configuration has been pressed so as mach would stop running too?

Rick