# How common are missed steps? **URL:** \ **Category:** Original/PRO Series (Buildbotics) (Gen 1)\ **Created:** [January 24, 2023, 5:21pm UTC](https://forum.onefinitycnc.com/t/how-common-are-missed-steps/18352 "2023-01-24T17:21:09Z")\ **Posts on this page:** 1\ **Showing post:** 23
**Author:** ![WaywardWoodworker](https://avatars.discourse-cdn.com/v4/letter/w/e79b87/32.png) [@WaywardWoodworker](https://forum.onefinitycnc.com/u/WaywardWoodworker)\ **Post date:** [January 25, 2023, 9:08pm UTC](https://forum.onefinitycnc.com/t/how-common-are-missed-steps/18352/23 "2023-01-25T21:08:10Z")
The ones I used are no longer available but were similar to these: > **[3Pcs LJ12A3-4-Z/AY M12 Approach Sensor Inductive Proximity Sensor Switch...](https://www.amazon.com/Proximity-Switch-6-36V-Detecting-Distance/dp/B09J4L36RW?tag=benmyers-20)** > > 3Pcs LJ12A3-4-Z/AY M12 Approach Sensor Inductive Proximity Sensor Switch Detector Non-Shield Type PNP NC DC 6-36V 200mA 4mm Detecting Distance 3 Wire for 3D Printer Probe Bed Leveling,MCU Board: Amazon.com: Industrial & Scientific I specifically used a normally closed setup so if there was ever a failure of the wiring it would cause the machine to stop rather than crash into the end stops. Because they required 12-36v and the Onefinity controller operates at 3.3v I initially used a relay board I had between them but eventually moved to an optoisolator once I could get one to avoid the mechanical nature of a relay - both methods proved to be equally as accurate. Under normal operation the relay would be held closed by the normally closed proximity sensor and would open during the homing cycle which would break the circuit on the 3.3v side to the DB25 breakout board. The basics of the mount looked like this, note the metal screw in the plate for the proximity sensor to detect. I can dig up the stl file for the mount, same one works on X and Y. I don’t have one for the Z, that was more “custom” and not something I’m proud of but it works 🙂 ![image](https://us1.discourse-cdn.com/flex022/uploads/onefinitycnc/original/3X/a/9/a91678c97c0b74ff23d208488c9be4a1f153d8dd.jpeg) --- _[View the full topic](https://forum.onefinitycnc.com/t/how-common-are-missed-steps/18352)._