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General Mach Discussion / Cheap and easy spindle index sensor for G540 and Mach 3
« on: September 19, 2010, 04:28:48 PM »
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/Shopping/Catalog/Sensors_-z-_Encoders/Inductive_Proximity_Sensors/18mm_Round_(AK-z-VK1-z-PKW_Series)/Extended_Sensing_Distance_(AK1_Series)/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.
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.