min interfering with stepper movement

Hi. I'm in the process of setting up the electronics on my darwin. I've got a sanguino running the mendel 5D gcode with the reprap host (all on a windows machine). I'm getting the following weird behavior:

y axis is working fine. I banged my z axis card, so that's not even plugged in at the moment. On my x axis card, when I connect the min sensor wire to pin 20 I'm able to move my motor in only one direction. When I disconnect it from pin 20 I can go in both directions.

Any thoughts about what gives?

Liav.

sounds like your min sensor is broken- that's the correct behaviour if the min sensor is always asserted.

something to check is whether you regain both directions if you stick something in your min sensor- if so, you need only switch the polarity in firmware instead of getting a new one.

also check that power is getting to the LED in the sensor

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Wooden Mendel
Teacup Firmware

I should clarify that I haven't *connected* the sensors. Just pins 6 and 7 from the stepper driver to sanguino pins 20 and 21.

L

liav Wrote:
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> On my
> x axis card, when I connect the min sensor wire to
> pin 20 I'm able to move my motor in only one
> direction. When I disconnect it from pin 20 I can
> go in both directions.

so you're connecting a cable with no sensor on the other end? Just trying to figure out exactly what you're doing and what's occurring as a result

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Wooden Mendel
Teacup Firmware

I'm using the gen 2 electronics with stepper driver v1.2 (see [reprap.org] for wiring diagram). The endstops plug into the stepper boards via the ethernet connector system, and then the stepper boards have wires for the min and max signal (pins 6 & 7 on the stepper boards) which go to various pins on the sanguino. I haven't connected any of the endstops to the stepper cards yet, but have connected the min/max lines. Y axis works fine, Z seemed to be sort of working, then I gave the card a good bang. X works fine when I unplug the min signal line from pin 20 on the sanguino, and will only go in one direction when it's plugged in.

I am a bit confused? Are the signal lines to the endstop inputs open? If so these can float either way if nothing is driving the line.

Another watch point, is if the sensor lines are run with the stepper lines, there can sometimes be enough crosstalk from the motor back current emf to cause false reading.

On my 20 year old CNC, there is enough back emf that if I have a lamp plugged into the spindle relay, the current from just spinning the stepper without power is enough to cause the relay coils to engage and the light to come on. Stepper motors are generators and must be treated so.

-julie

If the firmware is written properly, the sanguino itself should pull the lines up to 5v internally with a weak current source, however if the writing style of the FiveD firmware is anything to go by, this is as likely as not accounted for.

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Wooden Mendel
Teacup Firmware

try changing the truth table.

[dev.www.reprap.org]