Estop wiring on a parallel BOB
13 Nov 2014 20:07 #53065
by cparsons
Estop wiring on a parallel BOB was created by cparsons
After some experimentation I have got my Estop to work on my breakout board by feeding the Estop signal back into an input to the PC - using estop-ext
on one of the parallel port inputs wired in parallel with the Estop input to the BOB - inverted to flip the logic
When I break the Estop signal to the BOB (and consequently the signal to the input back to the PC) LinuxCNC shows 'Stop' on the status line - and indeed does stop, and needs to have the Estop switch released and be 'started' to carry on. Not sure why it does not show 'Estop' instead of 'Stop'??
If I disconnect the parallel port cable the Estop is activated - not sure if this is the charge pump signal on pin 1 being lost or the Estop input not being there - although I suspect the latter as if the BOB is not attached and powered up LinuxCNC cannot be 'started' until it is - I guess because the Estop input signal is missing, but I would have assumed as it is inverted the LACK of a signal would mean all is well and the PRESENCE of a signal would mean Estop was activated??
The way the Estop BOB output is wired is that 12v on the Estop terminals means the motors run and disconnecting either + or - (also disconnecting the signal back to the input on pin 10) activates the Estop - so Estop low means stop on the BOB and high on the input back to the PC (as it is inverted)
Does this sound correct?
I am happy that the Estop button will stop everything but would like to understand this better?
Chris
on one of the parallel port inputs wired in parallel with the Estop input to the BOB - inverted to flip the logic
When I break the Estop signal to the BOB (and consequently the signal to the input back to the PC) LinuxCNC shows 'Stop' on the status line - and indeed does stop, and needs to have the Estop switch released and be 'started' to carry on. Not sure why it does not show 'Estop' instead of 'Stop'??
If I disconnect the parallel port cable the Estop is activated - not sure if this is the charge pump signal on pin 1 being lost or the Estop input not being there - although I suspect the latter as if the BOB is not attached and powered up LinuxCNC cannot be 'started' until it is - I guess because the Estop input signal is missing, but I would have assumed as it is inverted the LACK of a signal would mean all is well and the PRESENCE of a signal would mean Estop was activated??
The way the Estop BOB output is wired is that 12v on the Estop terminals means the motors run and disconnecting either + or - (also disconnecting the signal back to the input on pin 10) activates the Estop - so Estop low means stop on the BOB and high on the input back to the PC (as it is inverted)
Does this sound correct?
I am happy that the Estop button will stop everything but would like to understand this better?
Chris
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14 Nov 2014 00:58 #53067
by cncbasher
Replied by cncbasher on topic Estop wiring on a parallel BOB
Chris ,
yes thats working correctly , estop is primarily a hard wired closed loop safety item , in the fact that it should shut down on a break of circuit , rather than a make.
this gives you a self checking safety point , then the estop circuit is a closed wired loop , so if a wire breaks or a faulty switch , it instantly stops the machine
where had it been an open circuit , you could have for argument a faulty switch and you would never know , until such times as you activated the estop , and you would then find it did not work . and possibly have a dangerous situation .
yes thats working correctly , estop is primarily a hard wired closed loop safety item , in the fact that it should shut down on a break of circuit , rather than a make.
this gives you a self checking safety point , then the estop circuit is a closed wired loop , so if a wire breaks or a faulty switch , it instantly stops the machine
where had it been an open circuit , you could have for argument a faulty switch and you would never know , until such times as you activated the estop , and you would then find it did not work . and possibly have a dangerous situation .
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