Magnetic (Hall Effect) Noise-free End Stops / Homing Sensors – Part 1

After reading some the Shapeoko community’s experience with mechanical end-stops, I decided to design my own hall-effect based sensor solution. I’m not saying I went about it the right way and there are probably better/cheaper/faster solutions, but it’s what I came up with. I should say, I was inspired by Kevin Patterson’s hall effect solution (love the red/green feedback LEDs.)  https://www.youtube.com/watch?v=vqU_5wZAX3s6

NOTE: This design has not been implemented yet. Still waiting for one more board from OshPark to arrive.

Features:
* 24V separate power supply for the hall effect circuit.
* Nominally high (active low) design.
* Opto-isolated sensors
* Higher sensor voltage (24V) in combination with some simple pull-ups an caps to help ride out any coupled transients.

I’ve built some acrylic holders for the sensor boards and a small enclosure for the main board. The concept is similar to Kevin’s in that I will have 6 sensors (2 for each axis) connected with inexpensive phone cord connected by RJ11’s to the main board. I’ll mount my main board to the side of my control box where the grblshield/arduino lives.

Enclosure made with the Shapeoko. Holds spindle power supply, Arduino, grill-shield, and speed controller.
Enclosure made with the Shapeoko. Holds spindle power supply, Arduino, grbl-shield, and speed controller.

The PCBs are available to purchase or download the gerber files (PCB build files needed by a board house to make printed circuit boards) from Oshpark.com.
Main Board: https://oshpark.com/shared_projects/RHwVNxOU1
Sensor Board: https://oshpark.com/shared_projects/B7TXAfxt2

FYI:
Schematics and PCB Layout software –> OrCad
Housing design: ViaCad + MeshCam

SCHEMATICS:

shapeoko_homing_circuit_sensor_board

shapeoko_homing_circuit_main_board

BOM: (Note: I recommend the DRV5023AJQDBZR for the Hall Sensor instead of what’s on the BOM. The one in the BOM is a latching version and shouldn’t be used.  Use Digikey PN: 296-38452-1-ND)

Digikey_Order_Shapeoko_homing_circuit

1 of 6 sensors inside an acrylic housing (unpopulated)
1 of 6 sensors inside an acrylic housing (unpopulated)
Main board housing and Sensor covers.
Main board housing and Sensor covers.
Original batch of PCBs from OshPark.
Original batch of PCBs from OshPark.
Testing the sensor circuit before the boards showed up.
Testing the sensor circuit before the boards showed up.
Getting some of the parts ready for the build including a little shield board to solder on the sensor inputs to the UNO.
Getting some of the parts ready for the build including a little shield board to solder on the sensor inputs to the Arduino Uno.

As I build and test this concept I’ll try to post my results. Hope this helps some of you.

Testing the new equipment – A train track for the kids

After Hours now has 3D printing and CNC machining capability for all the custom electronic fixtures and enclosure work that’s done (better then a file and a Dremel!!)  Well, of course the new toys tools needed to be put to the test.  The kids have a wooden train set that had an important wye track missing and Ebay failed us on a replacement.  What better opportunity?  We started with a 3D printed prototype to get the “customer’s” approval before finalizing the design in wood.  Good thing we had that design review because we needed a male coupling where a female coupling was.

One more thing, it’s a good idea to make sure when you export your g-code that you choose the right machine (MeshCAM has a selection of machines the g-code export is tailored to).  I didn’t on the first couple attempts and ended up with a mill cutting right through the middle of the almost finished track.  The final version in the picture is attempt # 3.

For those who care:

CAD work: Punch ViaCAD 2D3D v9

CAM: MeshCAM

3D Printer: XYZPrinting Davinci 1.0

CNC: Shapeoko 2 from Inventables

 

Shapeoko 2
Shapeoko 2
001
The prototype
Getting Started
Getting Started
Looking good... crossing my fingers at this point..
Looking good… crossing my fingers at this point..
Gotta keep it clean
Gotta keep it clean
It looks good, but is it the right size?
It looks good, but is it the right size?
Is After Hours an electronics company or toy business?
Is After Hours an electronics company or toy business?
Sweet Success!! Definitely better then a Dremel.
Sweet Success!! Definitely better then a Dremel.