Z axis probe to limit switch swap??

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Z axis probe to limit switch swap??

Postby jknightandkarr » 2017-Jul-Tue-21-Jul

Is it possable on the Printrbot Simple 1405 to get rid of the z axis probe n use a limit switch? This probe thing isn't working for me at all and with the design, is also a HUGE P.I.T.A to adjust!!! So hopefully someone can help me on this. It is all original minus Ubis 13 hotend and heated printbed, but everything else is the same.

Joe
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Z axis probe to limit switch swap??

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Re: Z axis probe to limit switch swap??

Postby RetireeJay » 2017-Jul-Tue-22-Jul

It's absolutely possible. How to do it depends on which specific model of Printrboard you have.

The original circuit, before the probe came out, used a 4.7k pullup resistor, and the end-stop switch held the pin at ground until the switch was touched. On Rev D boards, the 4.7k pullup resistor was actually built-in to the ATMEL chip. On Rev F boards, you have a transistor in between the external pin and the ATMEL Z sensing input pin, so there's a inversion. Depending on the model, there may or may not be a pullup resistor in the circuit on the input side of the transistor (some probes have "open collector" outputs; others have active pull-up and pull-down circuitry). You will have to do a bit of research.

If you want to avoid having to modify the firmware, then you'll need to emulate the probe's high and low states depending on whether or not you are "triggered". Once you do that, then simply never issue a G29 command. A G28 Z0 will suffice to lower the carriage until it triggers your switch. You will want to have a convenient way of precisely adjusting the trigger point. And it will be up to you to get the plane of the bed parallel to the plane of X-Y motion of the hot end.

Several of us old-timers don't have probes and don't want them. A good switch and a trammed bed work just fine with ultimately less hassle.
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Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
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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)
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Re: Z axis probe to limit switch swap??

Postby jknightandkarr » 2017-Jul-Wed-14-Jul

I have the Printrbot Rev F4 board. Thanks for the help. I definatly need it. I flipped the probe to outside of its original loc, but now the screws will hit it if i try it. Lol

Joe
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Re: Z axis probe to limit switch swap??

Postby Sagbot » 2017-Jul-Mon-20-Jul

The thread's a bit stale but Joe, if you haven't already solved it, one thing you can do is move the inductive probe to the back of the bot and use it as a Z switch (with G28 Z0 as Jay says). I saw one person mount the probe on Z-Y blocks, next to the Y motor and sensed the steel base below. Then you don't have to make electrical changes. The bed can be shimmed with washers or springs or rubber spacers.
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Re: Z axis probe to limit switch swap??

Postby jknightandkarr » 2017-Sep-Sat-12-Sep

No, I haven't messed with it yet, been WAAAAY too busy/stressed out/felt like crud. I am looking at it now. Thanks for the help!

I thought I could just move the Z-Probe to the outside of the housing, but while that DID free up ALOT of room for the adjustment nuts, the bed screws hit n no room on one side to sence with out mods, next thought is original location but cut out part of the <Y> bracket to open up the room I need to adjust the probe.

Joe

Edit: So far the only good place I have found to mount the probe to is the Y/Z Top Back plate near the Z-Axis lead screw. Just gotta figure out the mounting of it and the metal sensor plate that the probe needs. A Z-Axis limit switch directly from Printrbot would have made this much simpler......
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~Owner, Designer & Builder Killer K.A.R.R.
~Starfleet Captain Joe R.
USS-Titanic Registry Number NCC-1513
Launched: Star Date 48509.9 Galaxy Class, Titanic Sub-Class Starship Max Warp: 15.96
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