im confusing myself help if you can

[bertieboy]

ok still need to start my build thread just getting parts together....ok quick one,
so, im making up on my own torch round mount with 3 NPN no? or nc? 24v proximity switches, i will run 2 as breakaway switches and the third as a float switch. NC or NO? im confused ....running 240v as im in australia xp45 ...black tx board cheers again

[ShawnM]

NC is preferred and adds another layer of safety against broken or bad connections.

[cncsnw]

There are sometimes conflicting definitions of "normal" when choosing between "normally open" and "normally closed".

As Shawn notes, you want the switch input to be closed when all is well, and open when something is wrong.

Whether you buy N.O. or N.C. switches or sensors depends on how they will be mounted.

For example, if your breakaway switches are tripped/activated by the torch in its proper position, and are released/deactivated when the torch breaks away, then you should install N.O. switches or sensors, so that they will be closed when all is well.

If the switch or sensor is only tripped/activated when the torch breaks away, then you should install N.C. switches or sensors.

[bertieboy]

yes thanks guys... thats why i was confused. I get the one where the open signal is normal but then if that signal chain fails in any way, theres no telling anything has gone wrong because its still open. So back to round mount, that means i will go for NC for the 3 sensors in the ring... but hang on, if all 3 get disconnected when touch off lifts the ring slightly, wont the 2 acting as breakoffs stop the machine? the 3rd sensor is ok as its saying its found the work surface by ... i get that one.
then theres the sensor at the end of the table that detects the steel edge of the gantry and stops it. they have different distances to when they sense the stop...1mm 2mm 4mm etc. so the x axis beam flyin along would need 5mm to stop.. So that would be a NO and then get closed to activate, but again, its not good for if the system fails [cut wire etc] it wouldnt react as NO and its open!
so the cnc12 can change the acorn inputs outputs etc via software ? i get it but dont. time for some more vids cheers for both your help

[bertieboy]

time for vids to open my brain more lol

[cncsnw]

then theres the sensor at the end of the table that detects the steel edge of the gantry and stops it. they have different distances to when they sense the stop...1mm 2mm 4mm etc. so the x axis beam flyin along would need 5mm to stop

You are imagining the wrong type of installation.

You do not install a limit switch so that the axis moves straight towards it. In that case, if the axis does not stop in time, in will smash the switch.

Instead, you install limit switches so that the axis moves past it, just in front of the switch (e.g. with a 1mm gap). That way you can install the switch so that it trips while the axis is still, say, 10mm away from the hard end of travel; but the switch will not be damaged even if the axis continues all the way to the end.

A limit switch or sensor that is activated by the arrival of the axis at the limit should be an N.C. sensor, so that the circuit is closed through most of the travel, but the circuit opens when the axis reaches the end of travel and trips the switch.

[bertieboy]

then theres the sensor at the end of the table that detects the steel edge of the gantry and stops it. they have different distances to when they sense the stop...1mm 2mm 4mm etc. so the x axis beam flyin along would need 5mm to stop

You are imagining the wrong type of installation.

You do not install a limit switch so that the axis moves straight towards it. In that case, if the axis does not stop in time, in will smash the switch.

Instead, you install limit switches so that the axis moves past it, just in front of the switch (e.g. with a 1mm gap). That way you can install the switch so that it trips while the axis is still, say, 10mm away from the hard end of travel; but the switch will not be damaged even if the axis continues all the way to the end.

A limit switch or sensor that is activated by the arrival of the axis at the limit should be an N.C. sensor, so that the circuit is closed through most of the travel, but the circuit opens when the axis reaches the end of travel and trips the switch.

cheers, Ive got a much better understanding of them now. I will buy a couple of each to play around with and look at remounting the x y and z end of travel sensors. cheers, Pete

[ShawnM]

Or..........you could save yourself a lot of time and money and just setup the axis software travel limits in the wizard and be done with everything. You don't "need" end of travel sensors if you simply setup the travel limits in the wizard. The machine will stop all by itself once setup. Just food for thought.