Firstly I have read and reread the wiki for the DuetWiFi,

3D Printing
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1

Firstly I have read and reread the wiki for the DuetWiFi, but cannot seem to find the solution to the issue I am having with using an NPN NO Probe for the the z axis endstop.

I have it wired up with a diode and connected to the E0 STP pin. When triggering it manually (by placing a metal object under it), both the LED on top of the probe and the LED on the DuetWiFi lights up. Which to me indicates the hardware is working as it should.

However when I home the Z axis, when the probe is triggered it does not stop the motor so the z axis just keeps moving up.

I must be missing something in the config. So if anyone can help, that would be great.

Is there anyone that has successfully used one of these probes on the DuetWiFi?

Config below.

config.g
; Endstops
M574 X1 Y1 S0 ; Define active low and unused microswitches
M574 Z0 E1 S1 ; Define active high microswitches
M558 P4 I1 X0 Y0 Z1 H10 F120 T6000 ; Set Z probe type to switch, the axes for which it is used and the probe + travel speeds
G31 P500 X28 Y12 Z1.20 ; Set Z probe trigger value, offset and trigger height

homez.g
G91 ; relative mode
G1 Z4 F200 ; raise head 4mm to ensure it is above the Z probe trigger height
G90 ; back to absolute mode
G1 X100 Y100 F2000 ; put head over the centre of the bed, or wherever you want to probe
G30 ; lower head, stop when probe triggered and set Z to trigger height

2

I know with my printers, I solder a voltage divider inline on the ground and signal lines for use with ramps boards.
They need the signal to output a lower voltage, 3.5v, down to 0.3v when triggered.

I don’t use a diode, just two resistors, 10K and 15K.

3

Have a look at this thread. http://forums.reprap.org/read.php?13,585345

4

Thanks guys, I might try the voltage divider method rather than the diode. I’ve also ordered some different diodes. So just need to wait until they arrive. This is the only thing holding up my hypercube build before I can do the first print. I’m so impatient when it comes to waiting for deliveries.

5

If your sensor is a NPN-type with open-collector output it can be connected directly to the limit switch input.

The sensor’s output switches on when triggered and sinks current from the limit switch input’s pullup resistor. There is no need for voltage dividers or diodes.

6

While it might work without, the diode is there to protect the board should the sensors ground be disconnected as recommended by the duet’s designer