[mrgame1988]

hi all,

If i was to drill a small hole in my spindle shaft could you rig a PNP or a NPN sensor to read the spindle speed? This is for my lathe but I am also considering doing this to my RF45 mill? How would you wire it in and would 5v be acceptable voltage?

Cheers Ryan

[dharmic]

I'd not be touching the spindle shaft, personally.

Pulley/gear on the back of it, maybe. I'd use a hall effect sensor and epoxy a baby neodymium magnet onto something that spins. Hall effect sensors can be had very readily that take 5V and ground, and pull an output pin down to ground when the magnet's in close.

This is assuming the sensor doesn't get swamped by EMF from the motor, of course. But I'd try the easy option first. Next step would be an encoder wheel and optical detector.

[mrgame1988]

I'd not be touching the spindle shaft, personally.

Pulley/gear on the back of it, maybe. I'd use a hall effect sensor and epoxy a baby neodymium magnet onto something that spins. Hall effect sensors can be had very readily that take 5V and ground, and pull an output pin down to ground when the magnet's in close.

This is assuming the sensor doesn't get swamped by EMF from the motor, of course. But I'd try the easy option first. Next step would be an encoder wheel and optical detector.

Ok i can spot the back of the pulley and glue a magnet in... what style hall effect sensor should i use... obviously it will need to be adjustable wont it?

[dharmic]

Sorry, don't know off the top of my head. Time to do some research. RS Australia | World Leading Distributor of Electronics, Electromechanical and Industrial Components is your friend. Adjustable? Nope, probably no need, you'll just need to get the spacing off the magnet right so it trips reliably.

[109jb]

http://www.cnczone.com/forums/mini-lathe/78131-cnc.html

[mrgame1988]

Ok, So.... If i mount a small neobendium magnet on my shaft / pulley I can use the following style sensor to pick up the magnet pulse per revolution?

njk-5002c sensor proximity switch npn 3-wire normally open+magne hall effect i8
Hot Sale NPN 3-wires normally open DC 5-24V Hall Effect Sensor Proximity Switch

So once its physically mounted:
Wiring: brown - Power+ , blue - Power- , black - signal

Black signal wire goes directly into my BOB and within Mach3 configure say "input3" as a spindle index?

Cheers Ryan

[dharmic]

Sounds about right. You also have to set up your input3 as a pin/port pair and "active low", I think.