WZ9V build log

[regressedEE]

Here's the limit switch circuit I'm using. One end of the limit switches goes to 12V (24V is also ok). The other ends go through current limiting resistors (a 1.0 kOhm resistor might work a little better) to the anodes. The cathodes are connected to ground. grbl already initializes the D9, D10 and D11 pins as inputs and enables the built-in pullup resistors, so just connect the collectors directly to the pins and the emitters to ground.

When the limit switch is tripped, current flows through the LED, lighting it up and pulling the transistor collector down to ground. Using the higher voltage helps drown out interference and the optical isolation adds another layer of protection against electrical noise.

The LTV-847 is a quad optocoupler so you can handle all of your limit switches using one chip, but really any decent optocoupler will do.

[RobCee]

A neat advantage of using limit switches that can handle 12v or 24v is that the higher the voltage they run at, the less they susceptible to interference. The 5v that the Arduino pumps out is very sensitive to interference.

[wz9v]

Thanks, thats the method I was going to use.

I was planning to use the H11L1 schmitt trigger logic output open collector version. The schmitt trigger should add some noise immunity and debounce but if its overkill I'm good with a simple open collector opto coupler also. My college digital circuits memories are slowly returning.

I looked up your part and that costs about 30% of what the parts I was looking at would. Of course we are talking $1 vs $3 but if simplier and cheaper will work why not.

[wz9v]

I was looking at the spec sheet and it says 20mA for the LED which would be 600 Ohms, 3.3K seems a bit high in your diagram that would result in about 3.5mA. After reviewing the charts that should be more than enough to work with the internal pull-ups.

Since the opto coupler is right next to the 328P I assume the internal pullups are good. Most of the people using more aggressive external pullups are not using an opto coupler in the middle. I actually prefer your setup and was headed in that direction.

[wz9v]

Woohoo, got my Makita mounts and new top Z-axis plate to allow for more clearance. My 500mm 2040 should be arriving today so I sandwich it between the two pieces of MakerSlide on X-axis. Have shielded cables and aviation connectors for steppers and almost have my limit switch wiring design sorted.

Might just be time to start making things move

[wz9v]

Didn't get as far as I would have liked this weekend. I did get my aluminum Makita mounts and got the Makita RT0701C and Z-limit switches mounted to the spindle plate. I have to do some work on the plates I got to reverse the Z-stepper to make clearance for the Makita. Took the machine mostly apart again while I wait for the bench top drill press to arrive so I can drill the holes for the 2040 to MakerSlide connections. Need to try and find some M5x40 and M5x60 BHCS screws now.

[noproblem]

WZ9v

You killing me now , where are the picture

[wz9v]

I have to drill the holes for the 2040 before I'll have pictures again. I'm sandwiching a piece of 2040 between the two MakerSlides on X which required extending the spaces to 2 7/8 and had to source some 90mm M5 bolts for the carriage. My plan for both y rails is to bolt a 2040 on the inside of the MakerSlide. Might be overkill but I figure the 1.25HP Makita could probably use a little help. Its kind of an experiment should I decide to scale up later.

I'm working on a quote for some of that Misumi flat extrusion for the bed also.

[wz9v]

Talk about snowballing. The Shapeoko finally became an excuse for that bench top drill press (coming Wednesday) along with a set of metric drill bits and a set of metric drill bits and taps.

[wz9v]

Didn't get any picures but drilled and setup the 2040 re-enforcements on X and Y this weekend.

Unfortunately the socket head bolts I used interfere with the locations I was using for the for X and Y limit switches. So more engineering to do along with some new Y-axis external belt brackets (to make them cleaner). Have to tell you, it does look beefy now with 40x40 rails on Y and 40x60 rails on X.