Hall effect proximity sensors

[cropwell]

Hey, if you don't need it or want it don't do it! :D

With decent screws and nuts I think a repeatability of 5 microns isn't out of reach, or even difficult, that's where I'm aiming with my next build, machining accuracy is likely to be closer to 15 but if you aim low you're bound to achieve shite results! :D

I work to an accuracy measured in Angstroms +/- a foot.



This is good enough for me, it is only woodwork

[routercnc]

I’ve just skim read this thread (funny in places !) so my answer to the first question which I think was essentially can I use Hall effect sensors instead of proximity sensors for homing -

They require a magnet to get close to the target to trigger and so like all magnets in the workshop will grow metal hairs and become unreliable. I have one to play with on my new E-kart foot throttle. Great if the magnet and sensor can be sealed in a box but I think one part must ride on the gantry for CNC machines if they are the sole sensor so they can’t be protected.

However for the auxiliary use as discussed they can be enclosed on the end of the stepper shaft at the rear of the motor or off the ballscrew and be sealed off. (Like the twist throttle of an electric bike).

[cropwell]

They require a magnet to get close to the target to trigger and so like all magnets in the workshop will grow metal hairs and become unreliable.

By Jingo, the man has a point !

[magicniner]

By Jingo, the man has a point !

So use a micro-switch for the linear sensor and an optical for the rotary! :D

[Voicecoil]

So use a micro-switch for the linear sensor and an optical for the rotary! :D

My thought as well, since slotted opto switches are common, just attach a slotted disc thingy to the ballscrew.

[cropwell]

Just out of interest, I thought I would see where the stepper positions itself with repeated homings using an inductive proximity sensor and a 5mm pitch leadscrew.

https://www.dropbox.com/s/xayeqtbo8l...P0009.AVI?dl=0

The video shows the stepper coming back to the same angular position and I tried it out 6 times with the same result, before I set up the camcorder.

I will leave you to draw your own conclusions about the necessity for a chopper

Cheers

Rob-T

[magicniner]

I will leave you to draw your own conclusions about the necessity for a chopper

I was only able to conclude the need for manual focus :D