Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: fatogga on August 01, 2008, 10:36:22 AM
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New to CNC but managed to get up and running until I went to set up limit switches but before I go there, let me explain that I'm suspicious of the cable I am using and would like to hear what I should be seeing on the Diagnostics screen under Port 1 Pins Current State.
With one so called parallel Cable I get lights 1 2 3 and 5 lit up with the rest off (reading from left to right). My motors turn accurately but when I connect a switch to Pin 10 and to common and press it, it doesn't light up.
So I went to Radio Shack and bought something called a Parallel MS/DOS Interlink Cable and now I get lights 1 thru 8 lit with the rest off but motors won't turn never mind the switches.
Please help.
Al
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Easiest thing do do if you have a meter is set it to Ohm range or continuity test if it has one. Check pin to pin on the cable to make sure there are no crossover wires as some cables are crossover rather than straight through.
Hood
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I checked all three of my cables and found only one "good" one ie. continuity on all pins. So that's ons thing out of the way.
Now on to my LPT1 port (JPG attached) Although it does use 378 it also shows 778. Is this a problem?
When I attach a switch to Pin 10, Port 1 and enable it, the diagmostic screen can't "see" it. If I check the active low it lights up but pressing the switch does nothing. I checked the switch for continuity and it is OK.
Very frustrating indeed
Al
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378 is the address you use.
Have you set it up in Ports and pins to have the limit on the port and pin and remembered to enable it?
If so and you are not seeing the LED for limits lighting then there is either a fault in your port(not really likely) or there is a problem further out. How are you connecting to the cable, are you using a breakout board? If so what kind? Can you try another pin?
Hood
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Yes, have set up port & Pin and enabled it. Now checking with Patrick at "Buildyourcnc" to see if I understood how to connect to BOB correctly. Will advise.
Al
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The purpose of the led display is a little confusing. What it displays is whether the computer sees an "active" signal on the pin, or not. (Not if the computer is seeing a +5v or not)
If in your case, the led lights when an "active low" is ticked means that the computer sees a low on the pin and says, that is active, and lights the led.
The normal state of the 5 input pins in the computer is +5v, because the computer is fitted with internal pull up resistors. This means that your BOB is putting a negative signal to the pin. Try the others and you will probably find that all the others are "active" on "active low" as well. This means that your BOB is reversing the signal to the computer.
A lot of the boards do this, and it is very confusing. What board is it.
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My BOB is a CNC4PC board model C10.
You can set pins 2 thru 9 as input or output, mine is set to output and you can set the 2 thru 9 common pins as ground or 5vdc, mine is set to ground.
The tutorial video instructs one to connect the switch to #10 and to common. (I tried this with 10 & 11 with same results ie no recognition whatsoever). BTY the connections to the switch are to the NC post and the C post.
Al
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I had a sneaking suspicion that it may be, seems to have been a few similar problems lately with the CNC4PC BOBs. Have you been in touch with Arturo to see what he says?
Hood
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Hi Hood,
Sorry, I missed this post until today. No, I haven't contacted Arturo but will send of a note to see what he has to say.
Tks
Al
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Hi Hood, This is what I sent to Arturo and his reply.
From: Al McLellan [mailto:lady@muskoka.com]
Sent: Saturday, August 09, 2008 3:39 PM
To: Arturo Duncan
Subject: Enquiry from CNC4PC
Hi,
I am trying to set up my limit and home switches using your CNC4PC C10 board and having problems.
Board jumpers are as they were from the factory, ie. pins 2-9 set as output and 2-9 common set to Ground.
When I hook switch up to Pin 10 (or 11 or 12) and the other wire to any of the 2-9 commons and set the port and pins in Mach3 to "enable" the program doesn't react in any way. ie No lights in the diagnostic screen.
However, if I hook up the switch up to pin 10 and then to any og the 5v sources, the switch is recognized but it physically doesn't stop the motor.
Tried all of the forums but no luck. Am I missing something.
Al
He replies as follows:
Al,
Sorry for the delay in getting to you. I was taking a couple of days off.
You have to go to: Config / Ports&Pins / Input Pins. There you have to assign the pins.
Have you done this before?
Is everything else working ok?
Thanks,
Arturo Duncan
As you can see, he missed the text where I said I "enabled" the ports and Pins and said nothing really. So I wrote back the following:
Hi,
I think I have it figured it out now. When I connect to pin # 10 and to 5v not ground and put a check in the active low box everything works. ie. when the switch is closed, the motor stops.
Originally, I was led to believe pin # 10 was supposed to be connected to ground!
Thanks
Al
He replied as follows:
Al,
I am glad all is fine now.
Thanks for letting me know.
OK, so I said I got it working in some manner but it's still not right according to the Mach3 set up video and I still don't know what's wrong.
I can get the machine to "Ref All Home" under this 5v scenerio, but it won't back off the "Z" switch unless I disable it and jog off then when I "Ref All Home" again, it homes the "Y"
but won't back off etc. as above.
At this point I'm ready to give up on limit and home switches but I realize this is foolish and would like to figure it out once and for all.
The funny thing is that I have the router working beautifully with mach3 and lazycam.
Can you come up with anything that might get me out of this delima?
BTW, Thanks for all your efforts thus far. I do appreciate it and realize this is a volunteered service with little reward other
than the satisfaction gained when you actually get a fellow CNC'er up and running.
Let's give it one last try.
Al
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Will have to have a look at Arturos board, will have time this evening (3:50pm now) and will get back to you if I find anything, sounds like Arturos board may be a sinking input but as I have never used them I dont know. Gotta go get a few jobs finished and they are not going well LOL
Hood
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Had a look and it seems you need 5V on an input pin for limits etc
You say you have that but it doesnt work right? If you connect up a NC switch (limit) and look on the diagnostics age does the LED light up when you press it?
If it des and you are still getting the problem try increasing the debounce to 2000 and see if it works correctly, if it does then lower the debounce until the problem reapears then back up again until it stops.
Do you have shielded cables on the limits?
Hood
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Hood, You are a genious!
I set debounce to 2000 and guess what, when I "Ref All Home" the "Z" went to "Home" and then backed off a bit and then continued on to the other Axes as expected and did the same.
Very confusing when following the setup videos that are trying to be Generic but don't work for all BOB's.
Many thanks for your help. You managed to get one more CNC'er up and running. Keep up the good work.
Now I can concentrate on doing something worthwhile!
Hope I can somehow contribute to the Forum in the future.
Al
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One final thing for the record, I wasn't using shielded cable to connect the Limit Switches in series.
Thanks again
Al
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Always best to shield the signal cables, especially when its 5v as noise is a real problem due to the small difference between a high and low signal.
Hood
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Trying to purchase shielded cable in a small town is frustrating since no one seems to know what it is.
We do have a Home Depot and they have something called CAT 5 Twisted pair cable but it doesn't specifically say it is shielded.
Will this work or could I use Coax Cable for this job. Do I ground the shield portion and if so where?
I am definitely getting interference from the 5v source. Too bad I can't use the common or ground sources on the board.
Al
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You can get cable from the internet easily enough and probably a lot cheaper than locally. I get a lot of my cables from eBay in the UK and you often get real bargains ;)
Cat 5 can be shielded but usually it is not, it is the the type of cable they use for networking computers and the twisted pair helps reduce noise but I dont think it would be so much help in limits.
Coax I think is usually just single core with shielding, you need twin core with shielding, also coax is often solid core and that should be avoided on a machine as vibration will eventually crack the core, you want multistrand cores as they are much more flexible and wont fatigue the same.
The shield should be grounded only at one end and it is best that it is the control end. Also try and connect all of your ground wires at one single point in the case.
Hood