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Author Topic: Index Pulse Setup Problems (Lathe)  (Read 6671 times)

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Offline Hood

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Re: Index Pulse Setup Problems (Lathe)
« Reply #10 on: September 15, 2011, 05:56:00 AM »
Wiring is ok with the exception of the limiting resistor on the white wire but you have changed that now.
Could be the input on the BOB that is the problem, try another if you have one free.
Hood

Offline mc

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Re: Index Pulse Setup Problems (Lathe)
« Reply #11 on: September 15, 2011, 08:12:42 PM »
Have you checked to see if the blue wire is switching using a muiltimeter?
Rather than start swapping parts, it's best to start with the basics, like is the sensor getting the necessary voltage, then see if it's outputting the correct signal before connecting it up.

However, having just ran through the datasheet for that sensor, the resistor on the input side may be a bit high.
Somebody correct me if I'm wrong in the follwing lines.
The datasheet calls for a typical forward voltage of 1.3V (max 1.8V) at 20mA.
Now for a 5V supply, we need a 3.7V drop across the resistor (5 - 1.3), and that limited to 20mA or 0.02A.
So using R=V/I, R = 3.7/0.02, which gives 185ohm, or for Vmax, 160ohm, so something between those two should work.

Also, is that a regulated 5V power supply you're using?
If it's not regulated, it may well be putting out well over 5V...

Another thing I've just noticed, is that sensor may struggle to output 5V to the BOB (it can only supply 6-7mA), so I'd go back to my original suggestion, and check the blue wire, first disconnected from the BOB, then if voltages are OK, connect it to the BOB and see if they remain the same.


An alternative sensor, with far simpler wiring is the PM series of sensors from RS. I used the PMR44P (RS no. 4805231) as the homing switch on my x-axis, or there is another sensor, which came on the spindle of my lathe, but I'd have to go and check it for the part no, but it was still available when I was hunting for the datasheet.

Offline Hood

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Re: Index Pulse Setup Problems (Lathe)
« Reply #12 on: September 16, 2011, 04:22:33 AM »
I think originally the resistance was worked out for 3.3v which I think would work out correct but having said that I have been using these optos for probably 8 years or more with 220ohm resistor and 5v and they have been fine. I have used them as index sensors and limits on various machines but only 3 different input methods to Mach, one was direct to port, one was via an  Acustep BOB and all the rest have been via PMDX 122.
Hood

Edit, actually that would make it worse thinking about it ::) Oh well anyway as said 220 has worked fine for me over the years but try the 180 and see.
« Last Edit: September 16, 2011, 04:26:00 AM by Hood »
Re: Index Pulse Setup Problems (Lathe)
« Reply #13 on: September 16, 2011, 04:43:59 AM »
Hood i checked  supply voltage and it is putting out 5v,im getting the 5v from the bufered BOB,i also tried a seprate 5v ps.    after you mentioned  trying a different input i was thinking about it and i think the inputs on my BOB have internal resistors so that simple mecanical switche can be used without pullup resistors. so i put the blue signal wire directly to pin 12 on the parallel port so it wont be affected by the BOB. it made a difference but still isnt right,now when i leave the switch open mach doesnt see any pulses wich i think is correct but when i use a pice of black tape to block the switch mach is reading  bettween about 8000 to 30,000 rpm >:(

regards
simon

Offline mc

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Re: Index Pulse Setup Problems (Lathe)
« Reply #14 on: September 16, 2011, 06:44:17 AM »
Have you tried disconnecting the blue wire, and seeing what voltage is on the blue wire when you block/unblock the sensor?

Also, when you put the put the blue wire straight to the PP, did you make sure the BOB was disconnected from that pin?

What BOB are you using?
Re: Index Pulse Setup Problems (Lathe)
« Reply #15 on: September 16, 2011, 12:00:12 PM »
MC sry i didnt have time to reply to your post this morning when i replyed to hood.    I will go check the voltage of the blue signal wire when the switch is blocked/unblocked and connected/unconnected from the PP.  no i didnt disconnect the pin from the BOB,i just teed into it infront of the BOB but i will go change that now.  dont think i have any 180 ohm resistors around but i will go get some tomorow and give that a try aswell                                    


regards
simon

Offline mc

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Re: Index Pulse Setup Problems (Lathe)
« Reply #16 on: September 16, 2011, 06:48:35 PM »
If 220ohm works for Hood, it should work for you aswell.

If you never disconnected the BOB, then the sensor will be fighting against it to control the signal to the PP, but start with the basics first.
Re: Index Pulse Setup Problems (Lathe)
« Reply #17 on: September 17, 2011, 11:16:43 AM »
ok i disconnected the BOB from the pin im useing so that it is connected directly to the PP. i also tried a coupe different resistors, the original 220 ohm was feeding the LED with 1.3v, the 180 ohm i tried was giveing 1.32v and the 160 ohm was giveing 1.32v aswell. the switch does give 0v and 5v depending on wether its blocked or unblocked. mach still is reading adout around twice asmany pulses as it should,also tried debounce with no luck. Im thinking maby its because im useing the BZ version and not just the B version that Hood is useing.


Hood, could you tell me where you got your switches from?  the ones i have are from RS conponents.

Is it worth me geting some ferrite bushes to try to get rid of any possible interference?  if so is there a particular type i should use? and should they go near the sensor or near PP?

MC, are the switches you use optical?



regards
simon

Offline Hood

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Re: Index Pulse Setup Problems (Lathe)
« Reply #18 on: September 17, 2011, 11:45:09 AM »
I get mine from RS,  RS number for 916B is  455-0896 and 917B is 455-0919

I used shielded cable with the cable grounded at the control end.
Can you attach your present xml and I will have a look as it does seem weird, you could try changing the active state of the Index just in case that makes a difference.

Hood

Offline mc

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Re: Index Pulse Setup Problems (Lathe)
« Reply #19 on: September 17, 2011, 06:39:06 PM »
Sounds a bit strange. Normally any interference causes random readings.
You don't happen to have a multimeter with a frequency setting?

I've also just ran through the datasheets for the B and BZ, and there doesn't appear to be any obvious differences. All the specs are identical, and having a quick scan of the optek website, it appears only the BZ is available now, so I doubt the Z means much to those using it.


All the sensors I'm running are optical. Not sure when I'll be in the workshop next, but I'll try and remember to check to see what the spindle sensor is, as I'm sure it was a good bit cheaper than the one I mentioned above.