Machsupport Forum
Mach Discussion => FAQs => Topic started by: cheryl on November 27, 2014, 04:25:19 AM
-
Still learning but help required.
1/ Can you use Mach3 with normally open limit switches, i cannot find a reference to this in the manual unless i have missed it.
2/ How can i use 24Vdc for my limit and home switches.
Any help appreciated, please keep it simple i am a lay person when it coms to electrics
Thanks Cheryl.
-
Hi Cheryl,
1) If you wish - Mach3 allows normally open or normally closed switches to be used (selecting Active Low / Active High as appropriate). Most prefer to use normally closed switches - supposedly it makes if 'fail-safe' if a wire falls off ( n.b. I use normally open switches and have never had a problem yet :) ).
2) You will need to use a Break Out Board or Controller that accepts 24 Volt input signals.
Tweakie.
-
Why i asked th questions is that i have built a controller that drives the machine ok apart from having random limit and e-stop activations.
I have used shielded cable for limit and e-stop wiring and stepper motor wiring but i still get the random activations.
I have been told by a local electrical engineer who works on manufacturing machinery, mainly servo drives, that they always use at least 24Vdc to their control circuits which eliminated any stray signals.
How can i stop these random activations.
Oh, i have switched off WatchDogs and have Debounce set at 1000.
-
The easy way is to set debounce higher. Try 3000.
Otherwise, make sure all your components are properly grounded using the star grounding method.
-
Thanks Gerry,
What exactly is star grounding method, any diagram.
Thanks Cher
-
2) you could use a simple 2 resistor potential divider to drop 24V switch network to 5V
-
Thanks stirling,
I am not an electrical person, so i do not know what this is.
Any pics or description/circuit diagram.
Thanks,
Cher
-
star grounding is where every component has it's own ground wire, all tied to a single point in the control box. If you google it, you'll find tons of examples.
-
Hi Gerry,
I`ll do that, thank very much for you help.
Cher
-
if you look here (http://en.wikipedia.org/wiki/Voltage_divider). On the diagram you see a simple potential divider.
Vin would be your 24V
suitable values for the resistors Z1 and Z2 would be 18K and 4.7K respectively
Vout would then be connected to a Mach input and would be at 5V
You'd put your switches in parallel between the 24V source and Z1
With all switches open, the 4.7K resistor would pull the input down to 0V
With any switch closed the input would be at 5V
-
I 'd made up this spreadsheet to help me. Taken from the same page that Ian linked too.
-
Thanks for the help, looks like i have a bit more work to do.
Cher