Need Help!- B!t(h of a time with the limit swiches...

[bikedude987]

So I am at the point in my conversion when I am wiring up the limit switches. They are normally open switches, so I wired them in parallel; if one trips it should close the circuit no matter which one. I wired one lead to pin 11,12,13 on the BOB, and have the 'minimum limit + home X' (same for Y Z) set to their respective pins. The other leads are grounded to the common pins on BOB, or set to 5v. Either way produces the same result: AXIS freaks out and acts like the limits are always tripped. I've tried inverting the pins, setting the polarities to 0 in the .ini file, and have made double sure they are actually normally open...they are.

Can someone tell me where the error is? or walk me through how to properly set up my limit switches?
one on each end of travel, normally open. emc@ W C10 BOB from Keling.
THANK YOU!!!

[CNC Lurker]

Not sure if it is different with your BOB, but Gecko recommends normally closed limit switches instead of normally open.

It's possible that you should be using normally closed switches instead of normally open switches.

[bikedude987]

i realize that normally closed switches are recommended, but the software should be able to work with either.
I am more unsure about the wiring than the configuration of EMC2, i think.

[xadon]

Are you using pull up resistors. If not put a 10k 1/4 watt resistor between the +5 and the input pin. If I remove the resistor mine does the same thing.

[bikedude987]

hmmmm....... you're supposed to use resistors.... see, this is news to me. no where that i read mentioned resistors, or really much of anything about the wiring. I will try bridging the leads with some resistors.

[bikedude987]

so I put a 10k 1/4W resistor between a 5v source and the input lead (11,12 or 13) on the BOB, now the machine gives me a 'joint # on limit switch error'.

another weird thing, i disabled the estop pinouts in StepConfig because it would read the estop as always on and I could not toggle it off in AXIS.

someone please tell me how to properly wire this!

[bikedude987]

ok, new development; now whenever I plug in the db25 cable from the computer, it disables the BOB. so, without the cable, the red led is on and shining - signaling that the board is enabled. as soon as you plug in the cable, the led goes off, and nothing moves.

i didn't change anything except the limit switch wiring, and it was working fine yesterday...

PLEASE HELP!

[bikedude987]

so the cable issue appears to be a computer problem, the machine works fine with my laptop. but we (the school) wants to use the machine with the PC... not my personal laptop.

the same limit switch error exists whether i have the BOB set to pull up or down, the polarity in the .ini file set to 0 or 1 and the pinout in stepconfig inverted or not...

what the heck is going on?

[chester88]

Is the parport in the right mode?
(usually set in the bios eg spp mode usually works.)

[bikedude987]

I have tried setting the port to a different mode, but nothing... weird thing is, it stopped working without me messing with any of the settings...

[xadon]

you might want to go over your settings for pin 11 12 13 to make sure they are all set the same. in EMC2 for an Normally open switch with pull up resistors it should be set to inverted. Also grab a volt meter and check the ohms to make sure your switches are wired correctly and not grounded to your mill or shorted.

[davidmb]

Hi Bikedude,

I had similar issues when adding limit and home switches to my emc2 setup, ended up adding an extra parport and some electronics at the machine end to buffer the signals to the pc. It looked like the pins on the standard parports that are available these days are really designed to do two way comms, the input pins do not all have internal pull up resistors but in input mode are high impedance inputs that make them prone to noise so I found it best to use a proper driver at the machine end, from a safety viewpoint it is prudent to use normally closed logic, that way if a cable fails the machine stops, the alternative is that you only find out that something has failed when the machine crashes. ( If you need a circuit I can dig out the details, pm me )