Auto-leveling - Wiring in the Z Probe Endstop Switch

[old man emu]

I have been modifying my i3 to allow me to use the Marlin update with auto leveling of the bed. I attached the parts that had to be printed, the servo and the micro-switch, and wired up the micro-switch to the RAMPS board. Since I wanted the protection of an endstop switch to prevent the extruder crashing into the printer plate, I kept the original Z-axis endstop switch.

I wanted to print something before I had the chance to upgrade the Marlin firmware, but I found that the original end stop switch would not stop the movement of the Z axis until I cut the connection between the Z probe switch and the RAMPS board. Here is a sketch of how these switches were wired up:

Z-Stop Switches.jpg

Have I wired the two switches correctly? If this is the correct way to wire them up, then I have forgotten to set the trigger rod correctly, and that is not an electronics problem.

Old Man Emu

[RobH2]

From your drawing I don't see that you are getting that "double" protection I think you are after. If the switch with the lever trips first it will not stop the machine and it will still keep going. These switches by default are allowing current to flow and the switch without the lever is still completing the circuit. Until it trips the machine will keep moving.

The color of the wires does not matter here. The switches are just creating continuity.

I believe that what you need is to wire them in series so that if either switch trips, the circuit is broken. I've provided a drawing of that. The switches can go in any order. The lever one does not need to be on the end.

Untitled-1.png

[Roxy]

From your drawing I don't see that you are getting that "double" protection I think you are after. If the switch with the lever trips first it will not stop the machine and it will still keep going. These switches by default are allowing current to flow and the switch without the lever is still completing the circuit. Until it trips the machine will keep moving.

The color of the wires does not matter here. The switches are just creating continuity.

I believe that what you need is to wire them in series so that if either switch trips, the circuit is broken. I've provided a drawing of that. The switches can go in any order. The lever one does not need to be on the end.

Untitled-1.png

I concur. If you had been using the switches in a 'Normally Open' configuration, the first way would be correct. (and the firmware would have to be configured for that too)

But if you are using the switches in 'Normally Closed' mode, then they need to be in series so that either switch opening up breaks the circuit.

[old man emu]

Thanks for that. I want them to be wired N/O as that is the way the original switch was wired. I'll run the wires again so that the two switches are wired in series.

OME

[printbus]

You meant to say N/C, right? Wiring two N/O switches in series won't work. Then BOTH switches would have to be activated in order for RAMPS to see a change.

[old man emu]

I'm so confused!!

I will wire them as RobH2 and Roxy suggest.

OME

[Roxy]

I'm so confused!!

I will wire them as RobH2 and Roxy suggest.

OME

Get them wired up as suggested... And then we can take a volt meter to it and it will make perfect sense. Most micro-switches are standardized. If you are using the two outside pins, you are using the switch in the 'normally closed' settings. When the lever gets pressed, the switch will be 'open'. So with two switches in series, they both will be conducting current unless one (or more) of them's lever gets pressed.

With a volt meter, it will be very easy to probe the circuit and you will understand what is going on very quickly.