Dead Proximity Sensor?

Quote
dc42
There is very little to go wrong with the proximity sensor apart from the connections. Also there is no likely component failure I can think of that would cause that symptom. So I think the problem is more likely to be a bad connection (e.g. failed crimp connection ay one end of the output wire in the sensor loom), or possibly a fault on the Duet. How certain are you that the reading changes when you shine a light on it? What sort of light did you use? A modern LED flashlight is unlikely to have an effect, but a flashlight with an old fashioned bulb should. Is there much difference in the behaviour if you disconnect the sensor output wire (blue wire if it is an Ormerod 1) from the Duet?

Quote
c0rtex

Quote
dc42
There is very little to go wrong with the proximity sensor apart from the connections. Also there is no likely component failure I can think of that would cause that symptom. So I think the problem is more likely to be a bad connection (e.g. failed crimp connection ay one end of the output wire in the sensor loom), or possibly a fault on the Duet. How certain are you that the reading changes when you shine a light on it? What sort of light did you use? A modern LED flashlight is unlikely to have an effect, but a flashlight with an old fashioned bulb should. Is there much difference in the behaviour if you disconnect the sensor output wire (blue wire if it is an Ormerod 1) from the Duet?

Yeah, I used my desk lamp (incandescent) and the values changed but like I said only by a negligible amount. I suppose that I can check for a bad crimp. Everything else is working perfectly fine on the Duet. Would rather not have to ^^ wait 2 weeks for another part.

Quote

Sorry you are having problems with your proximity sensor. I'm assuming you have an Ormerod 2? It sounds like you have already worked through the list here: [reprappro.com]

If you have checked the wiring is connected correctly (you can always send me a picture if you would like me to check it for you), there's a couple more tests you can do, first to check the voltages on the proximity board and wiring, and then to check the Duet is functioning correctly.

You can test the voltage on the proximity board with a multimeter. Measure the voltage with the red multimeter probe on the pins on the back of the Proximity sensor board, where the wiring loom connects to the board, and the black probe on 12V ground screw terminal. Make sure the probe is in '4-wire' mode by sending 'M558 P2'. As an example, I did this and got the following:

Probe reading: 3 (4) (nothing under the probe)
Red: 20mV
Yellow: 2.5mV
Blue: 1.29V
Green: 3.27V

Probe reading: 953 (955) (white paper close to the probe)
Red: 1.53V
Yellow: 2.5mV
Blue: 1.29V
Green: 3.27V

The red wire, which carries the sensor reading, reads half the of the voltage at full saturation, as it is turned off half the time, as the probe modulates. The Blue wire carries the modulating voltage to the infra red LED in the sensor, so it also shows half the voltage. There is a voltage drop on the Blue wire, as it powers the LED.

You can also turn the modulation off, and measure the voltage on the pins of the probe. Send 'M558 P1', then check the voltage. I get:

Probe reading: 1
Red: 25mV
Yellow: 5.6mV
Blue: 2.56V
Green: 3.27V

Probe reading: 955
Red: 3.06V
Yellow: 5.6mV
Blue: 2.56V
Green: 3.27V

This should show if there is a problem with the sensor, or if there a problem with a poor connection on one of the wires.


To test the Duet, check the voltages on the pins where the wires from the proximity loom connects to it (see [reprappro.com] ):
Test between Green (+3.3V) and Yellow (Ground), this should be around 3.3V.
The Blue pin should provide 1.65V (M558 P2) or 3.2V (M558 P1).

You can also test the Duet response is correct, without the sensor connected.
Short circuit the red pin to ground (the metal cover of the SD socket) with a piece of wire, the G31 response should be '0 (0)'.
Then put a jumper between the red pin and blue pine, the G31 response should be '1021 (1021)'.

If this works okay, send me a good picture of the back and the front of the proximity sensor, so I can see if there is a problem with it. Let me know your results from the above tests, and I'll try and work out what has gone wrong. We try to give you the information to diagnose the problem, so if you do need a replacement part, you get the correct one!