Cheap and easy spindle index sensor for G540 and Mach 3

[grizzlymog]

Here's some details of a spindle index sensor I'm using on my smithy cnc retrofit project. I have a couple of inductive proximity sensors (http://www.automationdirect.com/adc/...ies)/AK1-AN-3H) on my plasma cutting gantry and figured one would make a good spindle index sensor. I've used these for years and they are super tough, surviving heat, molten metal spatter, and splashing from the water table. I found they work great as a spindle index sensor too. At 18mm dia. they are a bit large, but smaller, 12 and 8mm sensors are available.

Mach 3 likes one index pulse per rev to index the spindle rpm. I epoxied a short piece of light gauge steel angle to the back of my spindle pulley for the trigger, and mounted the sensor a few mm away so that it would sense the trigger and not the pulley (see pic). The sensor has a built-in LED which helps in adjusting the gap distance.

The wiring is straightforward. I used a 12v wall power supply to power the sensor which likes 10-30 VDC. I used a multimeter to identify the lead polarity, then connected (-) to G540 pin 12, (+) to sensor positive, and NO sensor output to G540 pin 1 (see diagram).

I tested the RPM seen by Mach with a cheapo laser tachometer and the results were identical over the full range of my lathe pulley combinations (~169-2124 rpm).

The cost of a new sensor is ~$25 and doesn't require any add-on encoder/decoder cards or slotted plates, just a small piece of scrap and some epoxy and you're good to go.

[Crevice Reamer]

$25? Cheap? Nice effort, but this Hall effect sensor is 1/3 of that cost and also a straightforward connection to G540:
http://search.digikey.com/scripts/Dk...me=480-1993-ND

http://cnczone.com/forums/showthread...=106312&page=6

To paraphrase Crocodile Dundee: You call that a bargain? Now THIS is a bargain.

CR.

[grizzlymog]

I learned a lot leading up to this project from reading through your many posts. You have a way of stating things in an easy to understand way and not overcomplicating an issue - very useful to a newbie. Thanks! I was considering the HE sensor that you found, but with my pulley/cabinet configuration it was going to be difficult to mount the thing, plus I already had these guys lying around...

Originally Posted by Crevice Reamer $25? Cheap? Nice effort, but this Hall effect sensor is 1/3 of that cost and also a straightforward connection to G540: http://search.digikey.com/scripts/Dk...me=480-1993-ND http://cnczone.com/forums/showthread...=106312&page=6 To paraphrase Crocodile Dundee: You call that a bargain? Now THIS is a bargain. CR.

[Crevice Reamer]

Ah so! A bird already in hand is cheap as cheap can be. And your epoxy angle mount is truly innovative. Kudos!

CR.

[Crevice Reamer]

BTW: That's a lathe isn't it? You should be using Mach3 Turn instead of mill. I know the G540B.xml downloads are mill configuration. You just have to make the M3Turn config files match.

CR.

[grizzlymog]

Actually it's a lathe/mill. I made a separate config for each. I'm still building the retrofit. I've finished the mill axis, now working on the x/y (or x/z in Turn) so 2 of the 3 motors are just spinning on the tabletop.

Originally Posted by Crevice Reamer BTW: That's a lathe isn't it? You should be using Mach3 Turn instead of mill. I know the G540B.xml downloads are mill configuration. You just have to make the M3Turn config files match. CR.

[dirtdiggler]

Grizzley mog,

Thanks for posting this with photos. I have been strugling for a long time trying to figure out how to get a spindle reading off of my Bridgeport series I. There is absolutely no place to put a spindle encoder. I actually have an old inductive promity sensor. It rated 10-30 @ 200Ma. The only place I can put this sensor is inside the head to read off the bottom Varidisk, and realizing this I can't use hal effect sensor. So, what do you use to trigger the sensor in your photo, is it just a piece of bent tin? This is genius, I love the simplicity. I just need to figure out how to wire it into my C23 breakout board.

[Jeff-Birt]

$25? Cheap? Nice effort, but this Hall effect sensor is 1/3 of that cost and also a straightforward connection to G540: http://search.digikey.com/scripts/Dk...me=480-1993-ND http://cnczone.com/forums/showthread...=106312&page=6 To paraphrase Crocodile Dundee: You call that a bargain? Now THIS is a bargain.

I have used both of these sensors, the inductive prox and the vane type hall effect sensor. The inductive prox is much easier to use for a spindle speed sensor. Both the mounting bracket needed and the target are much simpler/easier/cheaper to make. With the vane type sensor you need to affix a slotted disc made of metal to the pulley and you wind up with a very fast spinning knife (ouch!)

[dirtdiggler]

I agree. If time if is money then the proximity sensor idea make more sense. I'm finding that with DIY projects you need to pick your battles. To save an extra $15 on something that will take an extra 2-3 hours to fabricate and install it's just not worth it. I also like the fact that inductive proximity sensors resists dirt, grease and noise well. Does anyone know how I would hook one of these up directly to regular breakout board to get reading in mach 3? Is it as simple as supplying power to it and hooking it directly to an input pin on the BOB, or do I need another intermediate component?

Originally Posted by Jeff-Birt I have used both of these sensors, the inductive prox and the vane type hall effect sensor. The inductive prox is much easier to use for a spindle speed sensor. Both the mounting bracket needed and the target are much simpler/easier/cheaper to make. With the vane type sensor you need to affix a slotted disc made of metal to the pulley and you wind up with a very fast spinning knife (ouch!)

[Jeff-Birt]

Does anyone know how I would hook one of these up directly to regular breakout board to get reading in mach 3?

The answer is 'it depends'

On a G540 is your sensor is an NPN, open collector sensor then you just need to hook the sensor to the appropriate power source (that shares DC Common with the G540 supply) and then hook the sensor output to the G540 input.

Depending on how the inputs are set up on your BOB you may need a different type of output sensor.

[grizzlymog]

I'm not sure it's ingenious but it's simple. Yes, I just used a piece of bent steel but any piece of ferrous metal will do. Obviously you want a piece thick enough so that it won't flop around and smack the sensor. I used a 2-part epoxy to cement it to the back of the pulley and it's held tight so far.

Originally Posted by dirtdiggler Grizzley mog, Thanks for posting this with photos. I have been strugling for a long time trying to figure out how to get a spindle reading off of my Bridgeport series I. There is absolutely no place to put a spindle encoder. I actually have an old inductive promity sensor. It rated 10-30 @ 200Ma. The only place I can put this sensor is inside the head to read off the bottom Varidisk, and realizing this I can't use hal effect sensor. So, what do you use to trigger the sensor in your photo, is it just a piece of bent tin? This is genius, I love the simplicity. I just need to figure out how to wire it into my C23 breakout board.

[FantomMfg]

Is there a wire diagram on how to hook a hall-effect 3 wire sensor(same as crevicereamers) to a G540 for spindle indexing on an X2? Does the hall effect need its own powersupply or can i just hook it direct to the G540?