Home Switch Problem

[Kev2960]

Hi all, i'm having problems with the wiring of my home switches, mach 3 doesn't seem to recognise them in the diagnostic screen but they are working, but incorrectly, you have to press the the switch a couple of times before the axis stops. at the moment they are connected up open circuit, so when the switch is pressed it becomes live i have swapped the wires but to no avail. I have no idea whats going on and i'm not sure how to configure mach 3 with regard to the inputs and outputs etc
The switch is a mechanical lever type as shown. any help would be most appreciated
one wire goes to earth in the control box and the other is pin. pins used are X=13 Y=12 Z=11

[john swift]

Hi Kev

what breakout board are you using ?
and how have you wired the switches ?

it looks like you have wired the switches as normaly open
( if a wire breaks the control will never see a switch close ! )

John

[Kev2960]

Hi John the bob looks like this. I have tried both normally open and normally closed

[john swift]

looking at the breakout boards inputs



when the limit switch is closed, the EL817 opto isolator's NPN transistor will ground the printer ports input pin

the breakout board does not have any pull up resistors to ensure a printer port input is at a valid logic high when the limit switch is open

this can be a problem with PC's or laptops with 3.3V printer ports

John

[m_c]

looking at the breakout boards inputs



when the limit switch is closed, the EL817 opto isolator's NPN transistor will ground the printer ports input pin

Going back to this photo, my calcs based on the 1k resistor, means the opto should have 24V on the pin you've marked as 5V. At 5V, the 1k resistor would limit the current to roughly 3mA, whereas 24V would give roughly 22mA. Having had a look at the datasheet for the opto, it's expecting 20mA with a forward voltage of 1.2V.

Kev, have you measured the voltage at the top left pins on the optos?
Try using the bottom pin on the connector for gnd, and also the main power in gnd for the voltage measurements, just in case it's a gnd fault, not a positive supply fault.

If there is no voltage showing, is there power at the fan connector/is the fan working?
Would it be possible to get a photo of the underside of the board, so we can see where the power supply feed to the opto comes from?
Given the layout, I'd think the optos would take a feed from the same supply going to the fan connector, but without seeing the underside of the board, that is purely a guess.

[Kev2960]

Hi John, Im afraid I don't understand a word of what you've just said.....sorry!
Could explain please

[john swift]

Hi Kev
your micro switches are connected to your PC/Laptop printerport via opto isolators
(opto isolator part number EL817 - the terminal E goes to ground and C to the printer port input pin )

do you have a multi-meter to measure the voltage change at the printer port input pin when the switch is operated ?

how have you set up the switches in mach3's ports & pins ?
any thing like this -


John

[Kev2960]

Yes I've set the ports & pins and I'll check the voltage tomorrow
Thanks for your help I'll let you know how I get on

[john swift]

Hi Kev
printer port terminals


john

[Kev2960]

Morning John, yes the voltage on the pins are about 3.3 v
So what do I need to do next