"Also I would like to use the full 9 limit functions in Mach 3 (IE ++X, --X, ++Y, --Y etc). I have got this right, they are the limits per axis? Or am I missing something else here too.."
Yes, ++X, --X, ++Y, --Y etc refers to possible axis limits. But you still can use just one of them and as long as Mach stops when a limit trips, that is all you really care?
I generally don't get involved in setting up Mach as I don't use it, so what I have to say may be off base. But, the idea of hard limit switches is for the "aw crap" moment. Now having said that, If you want to use all of the named I/o points in Mach, I "think" you can call out the same pin number that you used for the others. As I said, this is for the "aw crap" moment when you want the machine to stop before it does harm to itself. I don't know if Mach tells you which limit has operated or not, but usually a quick glance at the machine will tell you where you went out of bounds.
Hope I am making sense.Art
AKA Country Bubba
(Older than Dirt)
Regards limits it's very easy and common practice to just wire them NC in series and use 1 input. The E-stop can be included in the series has well.
While Mach provides individual inputs for ++X --X and E-stop etc it doesn't care and any one switch tripping E-stops the system. This is why they can be wired in series along with E-stop.
In Mach you just tell the E-stop and all limits to watch the same Pin.
The only functionality you loose is that Mach won't light up the Individual Limit LED in diagnostics and instead light all the limit LEDs has well as the E-stop LED. But like Bubba says you'll know which switch has tripped by the crash bang wallop.!!
Another thing you can do to save Inputs is use Limits has home switches. When working and cutting Mach see's the switches and treats them has limits E-stopping the machine if tripped but when it's homing it ignores the switches has limits and uses them to indicate home position.
It does this by moving one Axis at a time Starting with Z axis then Y axis then X axis. Each time it hits the switch it stops, backs off the switch then Zero's the machine coordinate DRO's then moves the next Axis and does the same. This is why they can be wired in series because each switch is tripped then backed off to reset. In reality push any of the switches and it will set the position for the axis MAch is homing.? By this I mean you could trick MACH to set the X axis Home position by pushing the Y or Z axis switch. MAch doesn't know or care which actual switch was pressed all it's knows is that Pin (what ever) has changed state and stops and does it thing for that Axis it was moving.
What you can't do with series wired Home switches is Home ALL AXIS at the same time in one go. But this is not standard procedure for MACh anyway and to do this in MACH requires the Home all AXis macro altering anyway.
So with just 1 input used you have E-stop, limits and Homing leaving 4 more spare inputs on you typical PP.
Personally I don't like using limits has home switches so sacrifice another input and just wire the Home switches in series.
I do this mainly because don't actually run or use Limit's and E-stop switches thru BOB inputs like you would with 5V inputs on BOB using software driven E-stop has it's not safe enough for me.
Instead use hard wired E-stop system and run them thru Relays with 24v thru them to eliminate noise and potential false e-stops etc, I just use or control the 5v PP/BOB signal, again thru relay contacts to tell the software E-stop has occured and stop the G-code.
All powered devices are stopped by relays breaking the circuits so it's very safe and controlled. Only when machines safe will the system be allowed to restart via a dedicated momentary Re-set button.
This does however mean I can't use Limits has homes and that's the main reason I use separate Home switches on it's own input. Thou another reason is the ability to move my homing positions to any place on the table and not at the very extremes where Limit switches are usually located.
So to recap you only need 1 input if you want too or 2 at worst whether you choose to use software driven or hard wired E-stop system. Leaving 3 inputs for probes etc.!!
Last edited by JAZZCNC; 31-01-2013 at 12:55 AM.
The Following User Says Thank You to JAZZCNC For This Useful Post:
Thanks for getting back to me.
Good advice there!
OK, so, relays, check, 24v check, now going for two inputs (home+limit, makes sense!), one additional for now with the probe and both in respective series.
Still a little lost on the PP PCI card..
Is the one I posted earlier suitable?
(If so, I'll get it in straight away!)
Thanks in advance!
Suggest you go to Mach forum and check out some posts has it's been discussed a few times on there I think.?
If your only running a small machine or Lathe then checkout the Pokeys 56U or E has this will solve you several problems in one go.?
It's a 25Khz motion controller with either USB(56U) or Ethernet(56E) connection and gives 55 X Digital inputs 7 X analog 6X PWM outputs upto 26 Encoder pairs along with loads of other options plus it's MODBUS TCP so can be expanded to hundreds of inputs etc.
These are great for building Custom control panels and make using buttons to control MAch features easy. The encoder options also make it very easy to add a MPG for hand control movement or building a hand held Pendent.
Check it out here. PoKeys56E
I was really just looking to see if the PP was compatible in terms of ECP EPP etc? Not sure what comms Mach3 uses?!
Might have a look around some forums etc..
It looks like its a full PCI PP so I'm guessing it wont be an EMU..
Ma order it anyway as its so cheap, if it doesnt work at least I can return it ;D
Could someone please kindly check over my schematic to make sure I'm not making any obvious mistakes?
I plan to run 24v from a mains adapter, and the 5v/GND is running from the PP.
I decided to go for a good quality relay opposed to an opto simply because it makes more sense to me now to go this route.
Thanks in advance!
Last edited by cncnoob; 25-02-2013 at 04:39 PM. Reason: Schematic update.
It maybe makes more sense to you, but an opto with a suitable resistor (and zener if you want some extra protection) is far simpler. You can also add a capacitor across the opto if you want a simple hardware debounce.
But anyway, why D2? If it's a solid state relay, then you don't get any surges, so it's not doing anything.
Shouldn't R6 be connected directly to ground for quicker switching?
Fair enough a large capacitor over the input, but 100uF for C2 seems a bit excessive.
In fact, shouldn't R6 be tied to gnd to provide the voltage divider along with R1 and R2 for Q1?
It all seems a bit over complicated to me.
I was following a design for a relay originally which suggested the resistor R2 to be here..
It was originally for a realy, which I switched for an opto/SSR.
I've been working on this again today with a little help from another forum.
Not sure what value I should change up in terms of C2, any suggestions? I've changed it to a 50 for now..
This is the updated design (as of today..).
Last edited by cncnoob; 25-02-2013 at 09:09 PM.
By vputz in forum LinuxCNC/EMCReplies: 4Last Post: 15-10-2014, 08:51 AM
By Leadhead in forum General ElectronicsReplies: 1Last Post: 16-10-2013, 09:41 AM
By manofgresley in forum General ElectronicsReplies: 30Last Post: 02-01-2013, 02:08 PM
By davethefixer in forum General DiscussionReplies: 2Last Post: 23-09-2012, 09:12 PM
By Lee Roberts in forum Resources & HelpReplies: 13Last Post: 27-06-2008, 01:21 AM