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Author Topic: RPM and counting ?  (Read 12585 times)

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RPM and counting ?
« on: February 23, 2010, 05:13:25 PM »
Can any one tell me if I'm right here

In ports and pins/inputs iv got Index switched on so when i earth pin 10 on and off i get a rpm count on my screen.

Is this the right why about getting a rpm count on my screen if so is it OK to just use a hall effect sensor/pickup on my spindle. one pass over the pickup = rpm or do i need to look at this in a diffrent way.

Some thing like a disc with lots of slots in with a total diffrent type of pick up.

Either way can some one point me at a good set up/pick up to use 

Offline Hood

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Re: RPM and counting ?
« Reply #1 on: February 23, 2010, 05:19:31 PM »
Opto with a single slotted disc is the way I did it but others have used a hall effect sensor.

Hood
Re: RPM and counting ?
« Reply #2 on: February 23, 2010, 05:31:40 PM »
Just done a quick googel on a opto do i just run my pin 10 in one side and out the other back to earth or is there a bit more to it than that. 

Offline Hood

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Re: RPM and counting ?
« Reply #3 on: February 23, 2010, 05:46:08 PM »
I use an Optek OPB917B, you also need a current limiting resistor, I used 220 Ohm on mine for 5v.  http://www.farnell.com/datasheets/35000.pdf
You connect 5v  to the the VCC and 0V to the Gnd and also connect the 0V to the LEDs cathode. The LEDs Anode gets connected to the 5V but the resistor is in series with the 5V to limit the current. The Output is then connected to an input on your BOB.

Hood

Offline RICH

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Re: RPM and counting ?
« Reply #4 on: February 23, 2010, 07:30:58 PM »
hudmut,
I use a hall sensor on my lathe and works great. It was much easier to mount / implement that an opto with a single slotted disc when i did my lathe conversion.  So have used both with success. For a pickup i used a rare earth magnet from Radio Shack ( about 1/8" in diameter ) and just cleaned a spot and crazy glued it to the back of a gear. You will need look up the max current allowed by the sensor and limit it to the the sensor via a resistor. Just needed +5v / signal wire back as an input in MAch / and a grd.

RICH

Offline RICH

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Re: RPM and counting ?
« Reply #5 on: February 23, 2010, 07:34:17 PM »
« Last Edit: February 23, 2010, 08:45:59 PM by RICH »
Re: RPM and counting ?
« Reply #6 on: February 26, 2010, 04:42:58 PM »
thank you for all this boys got my head round most of it but the earth is the one that is doing me. iv got 3 wires on my switch. so iv got power going in from my power supply from the PC as well as my neg. so I'm left with one wire witch is my signal going back to pin 10 do i still need to earth as I'm going back to the PC all read thought My neg power supply

Offline Hood

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Re: RPM and counting ?
« Reply #7 on: February 26, 2010, 07:00:37 PM »
By Earth I am presuming you are meaning the 0V? If the 0V of the power supply is shared with the BOB then you shouldnt need to connect it to the BOB again but if its a separate power supply you may need to common the 0V of the supplies.
Hood
Re: RPM and counting ?
« Reply #8 on: April 02, 2010, 01:25:34 AM »
I am running into a similar situation.  I have a spindle sensor that I added onto my lathe CNC conversion and am having trouble getting it working.  The sensor requires 12 volts to power it and since I do not have a 12 volt source on my board (Hobby-CNC driver board) I am using an old PC power supply.  I have power going to the sensor and I have the "normally closed" wire going to pin 10.  The sensor also has a "normally open" wire which I am not using currently.  I can get a signal to show in my diags screen but Mach3 is not getting feedback from the sensor some how.  It does not show the Limit opening and closing when I rotate the spindle.  I attached a pic of the sensor, any ideas fellas?  Thanks!!

« Last Edit: April 02, 2010, 01:33:12 AM by ianober »

Offline RICH

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Re: RPM and counting ?
« Reply #9 on: April 02, 2010, 08:55:30 AM »
Like the other posts you will need an input to Mach in your config to say what pin / input and port is used for the signal.
I am curious as to what your sensor is reading off of. Are you reading off the gear teeth? ( Can't tell from the pic )
If so that would be timing and won;t work as you need a single index from a slot or magnet ( Hall sensor ).
Have a look at the Threading On the lathe Manual section 7 as that has info on configuration.
Post info on your sensor.
RICH