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Author Topic: Spindle RPM feedback, not low enough.  (Read 14648 times)

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Offline Katoh

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Re: Spindle RPM feedback, not low enough.
« Reply #20 on: January 24, 2013, 07:56:12 AM »
Hood, you got it spot on now, but yes from the earth buss bar if I can call it that it has a a way larger lead back to the cabinet and the actual lathe frame which is also connected to the main Ac earth wiring also, if that makes sense. I reckon (believe) I could easily confuse myself at times!

RICH, I'm using the latest lock down version of Mach, I believe it to *********.066 I downloaded and reconfigured the lathe about 3 days ago, after hood pointed out I'm using the wrong screen-set. Problem fixed now.

Gentlemen do you think maybe possibly it could be an input problem, say active high vs active low, I realize this in reality is the same as all it is meant to is be a trigger but maybe just maybe index needs to be opposite? The other thing could be, for example on my router the touch probe I could not just connect to the the BOB, I had to make a up a separate little board for it work correctly, using a few resistors and cap if I remember right. But the point with that is I followed some else s design to make it work. I'm a Civil Engineer, not an electronics engineer, I can't work this stuff out, thank goodness there are people who can.

Cheers
Katoh
Cheers
Katoh

Offline Hood

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Re: Spindle RPM feedback, not low enough.
« Reply #21 on: January 24, 2013, 08:04:51 AM »
Easy way to see if active state is correct is look at the diagnostics page and rotate by hand. If the LED is lit when the slot is allowing the LED to pass to the reciver then your active state is correct, if the LED is lit and goes out when you are blocking the signal then that is not right. Would still probably work but may not get a long enough off period for it to work effectively.
How wide is the slot on your CD? Also dont think a CD is ideal but more for the flex it could have rather than the reflective nature.
Hood

Offline Katoh

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Re: Spindle RPM feedback, not low enough.
« Reply #22 on: January 24, 2013, 08:31:20 PM »
Hood, you may be onto something here, as I have it setup with the index light on in the diagnostic screen, then switching it off when the notch passes the opto. Ill have a chance later this evening to change it round the other way.
The notch on the disk is 7mm wide. I used a formula that I found in the setup tutorials for notch size vs disk diameter vs max speed. The CD is actually great it spins true and is quite rigid, once bored out to fit the spindle, there's not really that much if it left.
Cheers
Katoh
Cheers
Katoh

Offline Hood

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Re: Spindle RPM feedback, not low enough.
« Reply #23 on: January 25, 2013, 01:50:13 AM »
I always had my slot 10mm wide, why I chose that I am not sure, probably just the cutter I had  ;D
Hood

Offline Katoh

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Re: Spindle RPM feedback, not low enough.
« Reply #24 on: January 25, 2013, 02:02:30 AM »
A little update.
I changed the settings on Mach and also on the board so now I have the index light on when the slot passes the opto, no slot no light. hold the slot on the opto and the index light stays on, move the slot it goes off. all good I hope.
It may be an improvement but still a problem in there, somewhere.
What I'm finding now is at max RPM 2000rpm I can get a stable reading with the debounce at 8 lowest value, but any rpm lower forget it. At lower rpm say 100 we need a debounce of 80, but still it will not give me an rpm over 500 or under 100.
I'm starting to run out of ideas, any more suggestions?

Cheers
Katoh
Cheers
Katoh

Offline Hood

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Re: Spindle RPM feedback, not low enough.
« Reply #25 on: January 25, 2013, 02:48:21 AM »
I am afraid I dont, it is just so strange that you need the Index Debounce so high. As mentioned any time I have used the Index pulse via the parallel port anything above 0 Index Debounce and it has made things worse.
 Is there any way you can temporarily  bypass your breakout board and connect direct to the parallel port? Even if that means temporarily disconnecting other I/O.
Think you mentioned how you were powering the opto but would have to read back to see so just make sure your 0v to the opto shares the 0V of the computer (or breakout if its isolated)

Hood

Offline Katoh

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Re: Spindle RPM feedback, not low enough.
« Reply #26 on: January 25, 2013, 04:09:29 AM »
I'm back to stage 1 here. the opto is code 121-7280 can be found on this page, about halve way down.
http://au.element14.com/jsp/level5/module.jsp?moduleId=en/206215.xml&sku=1173631
wiring as follows, black & Green are connected to one wire to pin 0v BOB,
                        Blue connected to pin 15 Input / Index
                        White is connected +5v
                        Red  is connected to +5v with an inline 220Ohm Resistor.

Again I am confused as the BOB led for the pin 15 input, registers each pulse without fail.
Maybe its simply a matter of increasing the size of the slot in the disk? It's not that hard to make another disk, maybe I should increase the size and add another 3 to 6 smaller slots and see what happens, maybe add 7 more go for Octo Disk, can only be defeated by "007" you never know your luck in the big smoke , it just might work!

Apologies talking stupid again, I have just run out of puff, maybe time to walk away from this problem for a while.

Many Thanks Again
Katoh
« Last Edit: January 25, 2013, 04:11:18 AM by Katoh »
Cheers
Katoh

Offline Hood

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Re: Spindle RPM feedback, not low enough.
« Reply #27 on: January 25, 2013, 04:37:59 AM »
Only thing I can think of is signal is not passing through the BOB correctly.
As said in the previous post I would try and connect direct to the port and see if that helps, remember power must share the computers 0v if you do it that way.
You can add as many slots as you want but as far as I know Timing is no longer in use so you would be wasting your time, that however may not be the case and maybe I am remembering incorrectly.
Hood

Offline RICH

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Re: Spindle RPM feedback, not low enough.
« Reply #28 on: January 25, 2013, 05:50:28 AM »
Timing is no longer supported, don't activate it, use single slot. Single slot is just as accurate.
Use the formula for the slot width as a guide. I found i had to
make it wider if the higher rpms were not seen. Use a flat black painted CD for the disc on the Sherline, in fact have one disc with multiple slot widths of varying widths just to play with. Put black tape over the slots so only one is seen.
Debounce here was usualy 10, below that was not good and above, say 100 that took to long to confirm the index signal.
Each system is different so just need to play. Lower the better. I changed to Hall sensor and found that to be far supperior. BTW, not all Hall sensors are the same for sensing  time, some are slower and you won't be able to use for high rpm's.

By pass the BOB, make things as simple as possible so you know if something is affecting the index.

I'll be out and about for and back in a few days. Didn't get a chance to play around last night nor get a few definitons
asked about.

RICH


Offline Katoh

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Re: Spindle RPM feedback, not low enough.
« Reply #29 on: January 25, 2013, 06:47:43 AM »
Thanks Hood
Thanks Rich

What Ill do, is bypass the board, and just connect  pin 15 input and 0v straight up, see what happens. I'm lucky in the respect that I'm using two boards from for inputs and one for outputs, Ill leave the outputs the way it is so I can still control the spindle.
I will post my findings over the weekend, after having the chance to do this.
One thing Ill ask before surgery, would the computer kernel, speed have anything to do with this?

I have a big Bridgeport mill sitting under my verandah, my next NC project. Goal is to have the router, lathe, and the mill, but seriously I'm thinking that using Parallel Port on the mill is going to give me grief like this, I'm be looking for a better system.

Once again Thanks Muchly
Katoh

Just to add I might send Peter Homman an Email regarding the situation, he might shed some light on this matter, its his BOB's I am using.
« Last Edit: January 25, 2013, 06:52:55 AM by Katoh »
Cheers
Katoh