Limit switches on motor plates?

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marcohess
Posts: 22
Joined: Sun Jul 08, 2012 4:41 am
Location: Adelaide - South Australia

Limit switches on motor plates?

Post by marcohess » Fri Jul 13, 2012 4:44 am

There are some nice and clever suggestions for setting up limit switches, but all I have seen so far are mounted on the end frames.

Disadvantage of that location in my mind is that there is an extra set of wiring that needs to be put somewhere.

Would there be anything wrong with mounting the limit switches on the motor plates?

In that way the wiring can go through the same loom as the motor wiring and in my mind the wiring is neat and out of the way.

A solution could be similar to the PCB that Karl designed but use a switch that is mounted on its side (like the D2F-L-A1 http://www.digikey.com.au/product-detai ... -ND/368468).

Marco
ShapeOko #290

potatotron
Posts: 135
Joined: Sun Apr 29, 2012 12:47 am
Location: Southern California
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Re: Limit switches on motor plates?

Post by potatotron » Fri Jul 13, 2012 5:27 am

That's pretty much what I did.

I set my origin to rear / left / top so my switches are wired like this:

Y - I had to add a small wood block to the rear frame to get the switch to press at the right spot (on my ShapeOko the left side hits the rear frame a few mm before the right side)

X - An extra wire pair (brown in the pic) runs between the X motor plate and the Z plate.

Z - A bolt in an insertion nut trips the switch, located just below the Delrin nut for the Z threaded rod.

One thing to note -- if you run the switch wires and motor wires together then they'll see a lot of noise from the motors since the stepper drivers are constantly pulsing current through the motor coils. You may have to add RC filters to your switches (I did). Karl's boards have these built in; I had to make them myself but it was really easy:

ground -> .1uf capacitor -> switch wire + arduino pin + 10K resistor -> +5V

2nd switch wire -> ground

Good luck!
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Karl
Posts: 75
Joined: Tue Apr 17, 2012 4:01 am

Re: Limit switches on motor plates?

Post by Karl » Fri Jul 13, 2012 10:47 am

marcohess wrote:There are some nice and clever suggestions for setting up limit switches, but all I have seen so far are mounted on the end frames.

Disadvantage of that location in my mind is that there is an extra set of wiring that needs to be put somewhere.
I would like to disagree on that, you still have to route your cables anyway.
I put my end switches on front, left and top.

The front switch cable is mounted inside the top part of the y-rail makerslide and exit at the back.

The left switch cable are routed inside the top part of the gantry makerslide and joins the motor cable on the right side.

The top switch cable are routed together with the Z-axis motor cable in the cable carrier to the right motor plate and joins the motor cables there.

From my limited testing it seems that none of the cables are limiting the movement on any axis.
Last edited by Karl on Fri Jul 13, 2012 12:52 pm, edited 1 time in total.
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ShapeOko #313

zimmer62
Posts: 81
Joined: Fri Jun 22, 2012 4:51 pm
Location: Lansing, MI

Limit switches on motor plates?

Post by zimmer62 » Fri Jul 13, 2012 11:46 am

I put mine on the motor plates... Superglue.

There are pictures of it here somewhere, maybe in the build log

zimmer62
Posts: 81
Joined: Fri Jun 22, 2012 4:51 pm
Location: Lansing, MI

Re: Limit switches on motor plates?

Post by zimmer62 » Fri Jul 13, 2012 1:47 pm

Here we go..

http://www.shapeoko.com/forum/viewtopic ... itch#p3347

The superglue actually works very well... I crashed the Z axis into the switch before I had the software setup correctly, and it broke off, gluing it back on was easy. I don't think they will break very often in the future.

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