Z Probe Reversed Signals

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Z Probe Reversed Signals

Postby waskan2206 » 2016-Dec-Sat-14-Dec

I have a Printrbot 1405 that seemed to have a faulty the Z probe. The light would go on and off appropriately but when I sent M119 it showed that it was always open. I followed some online advice and plugged the Z probe into the Y jack and vice versa and examined the M119 results under raised and lowered conditions. The suggestion was that I had a faulty sensor, which seemed right. So I bought a new sensor, and now I am finding that the Z probe indicates triggered when raised (and light is off) and open when lowered (and light is on). I can't find anything about this condition online. Can anyone help?
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Z Probe Reversed Signals

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Re: Z Probe Reversed Signals

Postby RetireeJay » 2016-Dec-Sun-07-Dec

The problem with the original probe was probably not in the probe itself, but the wiring connecting it to the board. For some reason, the "sense" lead on the original probes seems to be particularly fragile and suffers "fatigue failure" where it gets bent back and forth at a point. This has actually been discussed several times here at Printrbottalk. If you still have the original probe, you may be able to fix it by repairing the wire.

What version of Printrboard do you have? Different versions use the probe differently.

Many probes require 12V for their power, and that is not going to be supplied by the plug for the Y axis switch.

Apparently the new probe you bought has inverted logic. If you look closely at the documentation for the probe, maybe there's an option to connect it differently and get the correct logic.
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
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Re: Z Probe Reversed Signals

Postby wsguy » 2017-Jan-Tue-14-Jan

I'm having the same problem, printer was working fine and then would not home in the Z axis. The LED light works on the probe, but now the M119 command is showing open when metal is present and closed when it is not.

Guess I will try replacing the probe first, seems strange that the behavior would become opposite of what it had been doing. It happened after a long print. I a have a rev. F printrboard on my Simple Metal. If anyone has solved this issue short of replacing the printrboard would appreciate advice.
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Re: Z Probe Reversed Signals

Postby RetireeJay » 2017-Jan-Tue-15-Jan

wsguy wrote:I'm having the same problem, printer was working fine and then would not home in the Z axis. The LED light works on the probe, but now the M119 command is showing open when metal is present and closed when it is not.


The fact that M119 shows the state changing when metal is present or absent pretty much shows that the probe itself is working, the wire between the probe and the board is OK, and the interface circuit on the Printrboard is also working; so I suspect something in firmware settings. You must have done something. Did you re-flash your firmware? Check what you see when you query the EEPROM settings with an M503 command to see if there's a setting in there that controls the polarity of the Z probe sensing.
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
User avatar
RetireeJay
My next printer is...
 
Posts: 4587
Joined: 2013-Jan-Wed-13-Jan
Location: Greenville, SC
Reputation: 474

Re: Z Probe Reversed Signals

Postby waskan2206 » 2017-Feb-Sun-09-Feb

Thanks for responding RJ, and sorry for not reciprocating sooner. Mine is a Rev D. I had indeed tried to rewire the old probe with no success. Per your question for wsguy, before I had problems with the original probe, I did reflash the firmware to resolve issues I had connecting to the printer. That worked, at least it did for a while. As I was trying to fix the probe issue, eventually the connection issue recurred. Didn't see anything in Repetier menu of EEPROM settings to switch polarity. That's as far as I can get without connection flaking on me. I'll write more if I ever get that resolved. Thanks again!
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