Mach3 user - how do home switches work?
I've got a problem I cant seem to sort on my little DIY CNC router, my limit
switches don't work! 1) I've installed limit / end of travel switches on the x,y & z axes. 2) The switches are wired in series and wired to input 10 and enabled. 3) The switches are all normally closed, the input goes hi when switches operate. 4) In diagnostics I can operate any of the switches manually & the program senses it ok. But.... when I jog any axis or run some code to move an axis, operating any of the switches does nothing. I expected the motors to be disabled when I operated a switch. I've tried inverting the active level of the switches (ie hi/low active) and have tried changing just about every other setting. I've watched a couple of the mach3 videos (which have taught me a lot) but cannot find out what the problem is. Any clues guys? thanks |
Mach3 user - how do home switches work?
In article ,
"Dennis" wrote: I've got a problem I cant seem to sort on my little DIY CNC router, my limit switches don't work! 1) I've installed limit / end of travel switches on the x,y & z axes. 2) The switches are wired in series and wired to input 10 and enabled. 3) The switches are all normally closed, the input goes hi when switches operate. 4) In diagnostics I can operate any of the switches manually & the program senses it ok. But.... when I jog any axis or run some code to move an axis, operating any of the switches does nothing. I expected the motors to be disabled when I operated a switch. I've tried inverting the active level of the switches (ie hi/low active) and have tried changing just about every other setting. I've watched a couple of the mach3 videos (which have taught me a lot) but cannot find out what the problem is. Any clues guys? Yeah. Limit switches should cut the electrical power to the motors by means of relays, not computers, precisely so confused CNC cannot break the machine. Joe Gwinn |
Mach3 user - how do home switches work?
On Sat, 24 Mar 2012 21:42:00 +0800, Dennis wrote:
I've got a problem I cant seem to sort on my little DIY CNC router, my limit switches don't work! 1) I've installed limit / end of travel switches on the x,y & z axes. 2) The switches are wired in series and wired to input 10 and enabled. 3) The switches are all normally closed, the input goes hi when switches operate. 4) In diagnostics I can operate any of the switches manually & the program senses it ok. But.... when I jog any axis or run some code to move an axis, operating any of the switches does nothing. I expected the motors to be disabled when I operated a switch. I've tried inverting the active level of the switches (ie hi/low active) and have tried changing just about every other setting. I've watched a couple of the mach3 videos (which have taught me a lot) but cannot find out what the problem is. There are two reasons to put switches at known locations in the travel of an axis: 1: to keep from crashing the axis into something hard. 2: to let the controller know where home is. 1 and 2 are two different things, and on anything high performance, implementing 1 so you don't waste a whole bunch of travel is difficult or impossible. If your software is really using the switch as a _home_ switch and not a _limit_ switch, then it will only pay attention to the switch when it is homing -- and the homing algorithm will be something like "move the axis toward the home switch at a known safe speed until the switch opens, reverse direction and move _really slowly_ until the switch closes, then call that spot 'zero'". And, if your software is really _just_ using the switch as a home switch, then it'll happily go "past zero" in normal operation. Trying to implement a "don't crash" limit switch when you've got a motor that takes a while to stop even at maximum opposite current is a pain in the behind, because the mechanism _will_ keep moving for a while after you slam on the brakes when its going fast, but if you approach the switch slowly you'll need to power it in the desired direction to get it to finish up. About the only way out of that quandary is to have a normally-unused "shut-down lane" -- and who wants to pay for unused travel in their machine? -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com |
Mach3 user - how do home switches work?
On 2012-03-24, Dennis wrote:
I've got a problem I cant seem to sort on my little DIY CNC router, my limit switches don't work! 1) I've installed limit / end of travel switches on the x,y & z axes. 2) The switches are wired in series and wired to input 10 and enabled. 3) The switches are all normally closed, the input goes hi when switches operate. 4) In diagnostics I can operate any of the switches manually & the program senses it ok. But.... when I jog any axis or run some code to move an axis, operating any of the switches does nothing. I expected the motors to be disabled when I operated a switch. I've tried inverting the active level of the switches (ie hi/low active) and have tried changing just about every other setting. I've watched a couple of the mach3 videos (which have taught me a lot) but cannot find out what the problem is. I don't know Mach3, and it is probably a configuration in there somewhere. Something along the lines of "When you sense this -- STOP!", instead of "When you sense this, make a note in a logfile or on the screen and keep on truckin'. :-) Or is there a "E-stop override" in Mach3 somewhere? Could this be engaged? But first -- are you using steppers or servos? Steppers stop as soon as the computer stops talking to them. Servos keep moving at the last commanded speed until the computer says to change to zero inches per second (0 V command input to the servo amp). And in either case, the stepper driver or the servo amp should have a separate input to inhibit motion. This really should be connected. (Some servo amps have separate inputs to inhibit motion in the two directions, so you can have two limit switches, and still be able to feed it commands to back it off the limit switch. It would proably be easy enough to add those to stepper drivers too, if they don't already exist.) The "stop in any direction" input connects to the E-stop red mushroom button. Good Luck, DoN. -- Remove oil spill source from e-mail Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
Mach3 user - how do home switches work?
On 2012-03-24, Dennis wrote: I've got a problem I cant seem to sort on my little DIY CNC router, my limit switches don't work! Did you start here? http://www.machsupport.com/docs/Mach...all_Config.pdf Lloyd |
Mach3 user - how do home switches work?
There is a difference between home switches (used for homing, which
means precisely determining the coordinate system), and limit switches, which are used to activate the E-stop relay. The best practice is not to combine these functionalities in one. i |
Mach3 user - how do home switches work?
On Mon, 26 Mar 2012 14:07:32 +0800, "Dennis"
wrote: "Dennis" wrote in message .au... I've got a problem I cant seem to sort on my little DIY CNC router, my limit switches don't work! Many thanks for all the suggestions guys - for now I've given up! The switches work and the software senses them in diagnostics mode but I cannot get them to work as limit / end of travel switches. My machine is generally working & other issues like getting a better spindle than the existing Dremel are higher priority at the moment. Cheers When you ask something again, I'd consider a forum with a large Mach3 user base. CNCzone.com is one example. Karl |
Mach3 user - how do home switches work?
"Karl Townsend" wrote in message ... On Mon, 26 Mar 2012 14:07:32 +0800, "Dennis" wrote: "Dennis" wrote in message m.au... I've got a problem I cant seem to sort on my little DIY CNC router, my limit switches don't work! Many thanks for all the suggestions guys - for now I've given up! The switches work and the software senses them in diagnostics mode but I cannot get them to work as limit / end of travel switches. My machine is generally working & other issues like getting a better spindle than the existing Dremel are higher priority at the moment. Cheers When you ask something again, I'd consider a forum with a large Mach3 user base. CNCzone.com is one example. Karl Thanks Karl, I will. |
Mach3 user - how do home switches work?
not@home wrote in message ... On Mon, 26 Mar 2012 03:18:36 -0500, Karl Townsend wrote: On Mon, 26 Mar 2012 14:07:32 +0800, "Dennis" wrote: "Dennis" wrote in message om.au... I've got a problem I cant seem to sort on my little DIY CNC router, my limit switches don't work! Many thanks for all the suggestions guys - for now I've given up! The switches work and the software senses them in diagnostics mode but I cannot get them to work as limit / end of travel switches. My machine is generally working & other issues like getting a better spindle than the existing Dremel are higher priority at the moment. Cheers When you ask something again, I'd consider a forum with a large Mach3 user base. CNCzone.com is one example. or the machsupport group Thanks |
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