How to Wire Limit switches on Xylotex board.

[Ch4iS]

I have been trying to find how you wire up the limit switches.

I have all the wiring setup so I have 2 wires comming from each limit switch straight to the controller board.

But how do I wire them up?



I only have NO (normally open) switches which are already installed.


http://www.xylotex.com/FAQ.htm

I see how this can work, so do I just hook them (NO's) up parallel? does it matter if I join them all together? What is with the resistor?



{EDIT}

Found a few of my own questions :P

The resistor protects the parallel port from the excess current that it would receive were the pin directly hot wired to the power supply

Just wanted to know would this still work with Normally open switches?

[rodm]

Yes no problem with normally open switches.
In the settings Ports and Pins/Input Signal set as active low. Link them in series if you are using NO. If you are going to link all your limit switches together like this then it must be in series (meaning from one switch to the next) then just hook up to one pin 10 to 13 or 15 on the Xylotex board and the ground and echo the pin setting in the Mach3.

[Ch4iS]

Yes no problem with normally open switches.
In the settings Ports and Pins/Input Signal set as active low. Link them in series if you are using NO. If you are going to link all your limit switches together like this then it must be in series (meaning from one switch to the next) then just hook up to one pin 10 to 13 or 15 on the Xylotex board and the ground and echo the pin setting in the Mach3.

Do I need a resistor then?

also should I wire up the Z axis seperately so it can find the absolute height?

[rodm]

Yes to resistor or you might zap the parallel port and usually the motherboard.

Up to you how you want to configure your limit switches - there is a lot of variations

[Greolt]

If they are NO you will need to have them in parallel when sharing an input. Series if NC.

Unlike a BoB, Xylotex has no buffer or filter circuitry on the spare outputs and inputs. They just give you connectors to wire directly to the LPT.

You will probably need a 10k resistor between the 5v and the pin you are using.

Also if you strike noise issues you may need a capacitor, but worry about that if needed.

Greg

[rodm]

Hi Greg,
I hate this electronics mumbo jumbo. Help me here if I can be helped.
He wants to wire all his switches to one port. I thought if they were strung in a line one after the other (series) then that would be the way to do it. Any one switch closes and it goes low. Is it actually parallel and not series I am describing?

[Ch4iS]

If they are NO you will need to have them in parallel when sharing an input. Series if NC.

Unlike a BoB, Xylotex has no buffer or filter circuitry on the spare outputs and inputs. They just give you connectors to wire directly to the LPT.

You will probably need a 10k resistor between the 5v and the pin you are using.

Also if you strike noise issues you may need a capacitor, but worry about that if needed.

Greg

Yea, Motor cables are shielded and I had thought of that and if it is a problem I will have to unwind everything but if it has to be done it has to be done.

Ill solder everything up and see how I go, I should have a 10k lying around.

[Greolt]

Yes series would be the normal way to do it but with NC switches. Any one switch opens and breaks the circuit.

BlueRay has NO, so they will need to be in parallel. Any one switch closes and makes the circuit.

A picture is worth a thousand words. Click on them, they are animated.

Greg

[rodm]

Hi Greg,
Love the animation and have set this as a favourite so I can refer to it.

Where I got confused was with the NO and NC and for some unkown reason I had this reversed in my mind. blue^ray's thread had not been responded to so I chipped in but next time I will lay doggo and let somebody who understands this mumbo jumbo answer.

Sorry if I have caused any grief for you blue^ray.

Back out to the shed where the only person I can harm is myself and the dog.

[Ch4iS]

Sorry if I have caused any grief for you Chris.

na its fine, I know you and electronics



Just soldered everything up and I can only get the multimeter to read one limit switch (the smallest length of wire) so I cant tell if all are working fine.

The mutimeter has a battery sign so I just think the battery is running low.

Tomorrow ill just hook up a circuit with a led and see if the led lights insead of using the multimeter.


BTW reason for the new thread is that anyone looking for the same can search and find this thread.

[rodm]

Hi Chris,
Yes I do the same and post things that I think are interesting to other builders. If it is a novice it could be interesting and shows them a little of how it is done and anyone else can just skip past it.

Eventually this site will become a good reference for new machine builders.

Got half a day in the shed today so pleased to see some progress on my build.

[niall]

not sure about your one but in some of the ones Ive worked on the xy and z are wired as such that the are seen one after the other. I hope this helps.

[appiwood]

Hello Blueray

Sorry to butt in late, if you are using micro switches that have NO Comm NC contacts it can be better to use the NC contacts, the theory is that if you break a wire with a NO circuit nothing happens, if your limits are wired as NC, then if the circuit is broken by either the switch opening, or the machine chewing up a wire it all stops, just a nother layer of protection.

Ed

[Greolt]

......if you are using micro switches that have NO Comm NC contacts it can be better to use the NC contacts, the theory is that if you break a wire with a NO circuit nothing happens, if your limits are wired as NC, then if the circuit is broken by either the switch opening, or the machine chewing up a wire it all stops, just a nother layer of protection.

Yes there is logic there, but BlueRay already has his switches installed which only have NO conections.

What is better protection is to make good connections and secure wiring properly to avoid it getting chewed.

Just to clear up what seems to be confusion over the purpose of the resistor.

It is not to limit the current through the switch but actually increases it. By a very small amount. About half a miliamp.

The inputs that you connect to are by default at 5v or "high" when nothing is connected.

What the limit switch does is short the pin to ground and so bring it "low"

The current the pin has to supply when that happens is limited by circuitry inside your computer.

The "pullup" resistor in this case just helps the pin to stay at 5v until you bring it low (with the switch) and
in effect helping it, a very small amount, to resist electrical "noise"

Greg

[Ch4iS]

Hello Blueray

Sorry to butt in late, if you are using micro switches that have NO Comm NC contacts it can be better to use the NC contacts, the theory is that if you break a wire with a NO circuit nothing happens, if your limits are wired as NC, then if the circuit is broken by either the switch opening, or the machine chewing up a wire it all stops, just a nother layer of protection.

Ed

Yes I understood that when I was reading the xylotex guide. I will remember this in my next build.

* I only have 269 oz-in motors (bad choice at the time)
* I have a belt driven table

Worst case is I would guess it starts jumping teeth or stall after bending the limit switches arm. It has already done this (jumped teeth) but this was before I tightened the belts.