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limit switch issues..



brucer
08-13-2012, 06:19 PM
hey guys, been working on my machine in top secret mode.. got my bump stops mounted, got all my limit/home switches mounted and wired, I still need to wire my proximity switch for the floating torch, but that will be fairly basic I think, well at least I hope it is..


I'm running into a problem with my limit switches tripping on their own, I'm thinking signal noise might be doing it..

I have my limit switches wired in series, normally closed, I have the common on a ground on the break out board, and i have the last wire from nc on the switch ran to pin 12...
I set my inputs and homes and everything works fine.. i have it in machine coordinates a i ref all home and it runs hit the limit/home switches and zeros itself out, all is good...

I can let the machine set idle for a few minutes and it goes into limit switch tripped mode , i've put up to 4000 in debounce and it will still do it, just takes a little longer to do it..

any help or thoughts?

Gadget
08-13-2012, 06:27 PM
I was told to put a 1MF capacitor between the ground and limit switch connection on the BOB but to be honest I didn't see much improvement. I'v been thinking of wiring mine closed in series with the EStop. You might also try this Electronic home switches made easy! - Page 2 - CNCzone.com-The Largest Machinist Community on the net! (http://www.cnczone.com/forums/open_source_cnc_machine_designs/101878-electronic_home_switches_made_easy-2.html)
I played with the Hall Effect but I always got messed up when I hooked it up to my test board. Now I realize I didn't have opto isolation which allowed the HE transistors to show tripped at all times. I'll have to test it on the BOB, it would be great if it works.

Masseyman
08-13-2012, 08:02 PM
Is it a MicroSwitch or a Opto-Interrupter?

Opto-Interrupter

5666

brucer
08-13-2012, 08:11 PM
im using microswitches

Gadget
08-13-2012, 08:16 PM
I couldn't get an opto interrupter to work since they don't go to a true 0 volts when tripped. The BOB expects either 5V or 0V.

Masseyman
08-13-2012, 08:26 PM
I've had trouble with Micros on some other projects, tripping, then as the moving part settles, even just a little, it allows it to reconnect. Don't know what type of electronics you are using. Is there a way you can test to see if it stays "tripped"?


I couldn't get an opto interrupter to work since they don't go to a true 0 volts when tripped. The BOB expects either 5V or 0V.

Same here when I did my fishfeeder. I ran it through another NPN to draw it to Zero when it was interupted. After that discovery, it worked very well.

KHK
08-13-2012, 11:20 PM
Sounds like a power supply problem to me. Check with a quality DVM and see if it fades.

brucer
08-14-2012, 03:13 AM
Sounds like a power supply problem to me. Check with a quality DVM and see if it fades.

keith,

Do you have any suggestions on power supplies? I currently have a 24volt 14amp switching power supply, it is an import, and I am wanting to change to a 36vdc power supply anyways...

urbnsr
08-14-2012, 03:59 AM
Are you using shielded cables? I had a similar problem with mechanical switches and have not seen the problem return after replacing the cable with a new run of shielded cable. I do have seperate runs to each switch, but this setup uses the X and Y switches as both home and limit.

Paul

brucer
08-14-2012, 05:44 AM
Im running shielded cable on all my motors but not on the limit switches, I might need to go with shielded cable on the switches, but I dont see how you could ground each cable to each switch running in series.. I was told you could run normal twisted wire on limit switches if you run the switches NC and in series..

I'm going to try the capacitor first and see what that does..


Can you tell my electronics knowledge is pretty slim ;)

Gadget
08-14-2012, 06:36 AM
I ran it through another NPN to draw it to Zero when it was interupted. After that discovery, it worked very well.

Brilliant, I should have thought of that. I'll have to start saving them when run across them and try again.

Gadget
08-14-2012, 06:38 AM
I shielded my cables but still had the limits trip.

acourtjester
08-14-2012, 09:06 AM
Brucer
I had a similar problem with limit triggers and nothing showing on the diagnostics page just glitches. Here is a drawing of how I have mine hooked up (poor drawing skills) with annotations. I found with out hooking the shields to the ground rod I got glitches with nothing going on (like you said your having) when I hook the shields up it stops completely.
I also have pull up resistors on the BOB for the switches check this out Limit Switches~Solsylva CNC Plans (http://solsylva.com/cnc/limit_switches.shtml)
Have fun
Tom:joker

KHK
08-14-2012, 09:37 AM
keith,

Do you have any suggestions on power supplies? I currently have a 24volt 14amp switching power supply, it is an import, and I am wanting to change to a 36vdc power supply anyways...

Brucer, The limit switches are normaly on a 5v dc line. Your 24 v supply should be more than enough.

brucer
08-14-2012, 03:00 PM
Brucer, The limit switches are normaly on a 5v dc line. Your 24 v supply should be more than enough.

keith,

correct, but my drivers are rated to 50vdc, thats actually why I would want a bigger power supply, and I might as well get a better quality one while i'm at it.....
I'm running my break out board from a separate 5vdc power supply inside my enclosure..

brucer
08-14-2012, 03:03 PM
I got a 1mf capacitor and jumped it across the ground and pin 12 (limit/home switches connected to pin 12) set debounce at 2000 and that seems to have worked.

next up is wiring the proximity switch (oh joy), and then the water table, water table is cake compared to all this wiring that I suck at..

undercut
08-14-2012, 03:57 PM
I got a 1mf capacitor and jumped it across the ground and pin 12 (limit/home switches connected to pin 12) set debounce at 2000 and that seems to have worked.

next up is wiring the proximity switch (oh joy), and then the water table, water table is cake compared to all this wiring that I suck at..

Nice to hear the capacitor worked out. All of the other options would have been a hassle IMO.

Masseyman
08-15-2012, 08:02 PM
Brilliant, I should have thought of that. I'll have to start saving them when run across them and try again.

I forgot to mention I used a Pull-Down resistor on the NPN.

Ink-Jet printers are a great place to score the Interrupters. Normally 3 to 5 per printer.


I agree with Tom, A pull-up resistor should be used and IMHO, the printer port (pc connection) should be on the ground side of the switches. That way it is floating "low" instead of floating "high" when a switch is tripped. I am of course referring to the schematic in Tom's link. In theroy, if the connection is floating "high" it can incur inductance which may be enough to fool the software. To verify that theroy, a good DVM would have to measure any climbing RMS between the PC and 5V+ and the PC and ground.

Gadget
08-15-2012, 08:23 PM
I forgot to mention I used a Pull-Down resistor on the NPN.

Ink-Jet printers are a great place to score the Interrupters. Normally 3 to 5 per printer.


I agree with Tom, A pull-up resistor should be used and IMHO, the printer port (pc connection) should be on the ground side of the switches. That way it is floating "low" instead of floating "high" when a switch is tripped. I am of course referring to the schematic in Tom's link. In theroy, if the connection is floating "high" it can incur inductance which may be enough to fool the software. To verify that theroy, a good DVM would have to measure any climbing RMS between the PC and 5V+ and the PC and ground.
Any chance you could throw a rough schematic up on that setup?

Masseyman
08-15-2012, 09:19 PM
5691

I just love Eagle schematic software, it's free and easy to make good looking schematics.

Sometimes, what makes sense to me doesn't make sense to others. If this is confusing, let me know and I will give more detail. :)

undercut
08-15-2012, 09:59 PM
Picture is worth a thousands words. That makes sense even to me! LOL Gotta find me some old ink jet printers .... Will laser printers have any at all? I know they don't have a print head moving across but maybe they use them for paper feeding or something?

KHK
08-15-2012, 11:49 PM
5691

I just love Eagle schematic software, it's free and easy to make good looking schematics.

Sometimes, what makes sense to me doesn't make sense to others. If this is confusing, let me know and I will give more detail. :)

Do you have a link for the Eagle schematic software?

Gadget
08-16-2012, 07:01 AM
5691

I just love Eagle schematic software, it's free and easy to make good looking schematics.

Sometimes, what makes sense to me doesn't make sense to others. If this is confusing, let me know and I will give more detail. :)
Perfect, now I have more work to do. I'll get on it after I get the 3D printer operational.

Masseyman
08-16-2012, 01:45 PM
Do you have a link for the Eagle schematic software?

Freeware | Free PCB Design Software | CadSoft EAGLE | (http://www.cadsoftusa.com/download-eagle/freeware/?language=en)

This is a link to the freeware explanation page. It tells you how to get it from their site "Cadsoftusa.com". The short version is;
1. download the software
2. choose freeware version
3. register freeware version
It also produces gerber files for CNC machines.


@ Brucer - I totaly missed the post that you got the issue fixed with a filtering capacitor.



=gadget
Perfect, now I have more work to do. I'll get on it after I get the 3D printer operational.

I'm looking forward to see it in action!

undercut
08-16-2012, 02:52 PM
Freeware | Free PCB Design Software | CadSoft EAGLE | (http://www.cadsoftusa.com/download-eagle/freeware/?language=en)

This is a link to the freeware explanation page. It tells you how to get it from their site "Cadsoftusa.com". The short version is;
1. download the software
2. choose freeware version
3. register freeware version
It also produces gerber files for CNC machines.


@ Brucer - I totaly missed the post that you got the issue fixed with a filtering capacitor.

I'm looking forward to see it in action!


Thanks for the link. Will need to check the software out.

Masseyman
08-16-2012, 08:22 PM
Picture is worth a thousands words. That makes sense even to me! LOL Gotta find me some old ink jet printers .... Will laser printers have any at all? I know they don't have a print head moving across but maybe they use them for paper feeding or something?

Undercut - Sorry for the late reply! I totally missed reading your question.

Yes, Laser printers have them also. Your right, paper path sensing, and also sometimes open tray sensor, or lid open sensor.

undercut
08-17-2012, 12:14 PM
Undercut - Sorry for the late reply! I totally missed reading your question.

Yes, Laser printers have them also. Your right, paper path sensing, and also sometimes open tray sensor, or lid open sensor.

I know someone with a few laser printers that need recycling. I'll try to dissect them for parts before he does. Thanks for the reply! :D