Limit Switch Question

[CNCRob]

Hello,
I have a question about some limit swithes I bought for my machine. My machine came with three mostly just for homing it, but I used them for both limit and home. I just purchased 2 more for the other side of my x and y axis. They were prewired for my machine. I installed them but now when I goto home my machine it only goes a little ways( not even close to the swith)
and it stops and says its home. And when I tried to run a program it would run a few lines and stop, I hit enter again to start it back and I did the same thing. I then unhooked all the swithes and it worked fine. Also when I toggle any of the swithes they all work. The machine worked perfect with the first 3, the problem started after I installed the other 2. I am using CNCZeus for control software. I was wondering if anyone has any ideals what may be wrong or any settings I need to change to get it to work correct. Thanks-Robbie

[CNCRob]

I think I might have figured out the answer to my question tonight. Tonight was the first time since I have had the extra switches that I just sat down and tried to solve it. I tried nearly everything tonight from checking all the connections to replacing switches. Now I feel kind of stupid to tell what was actually wrong. It turns out in order to get all the extra wire out of the way, I just folded it together, and in doing so I kind of kinked the bends. Thats the only thing I can figure that would have been causeing it because after I straightend out all the kinks it seemed to work fine. I tried homing it several times and it worked everytime. It would not even work once with the kinks in it. I do have couple other questions now though. I need to do something with all the extra wire, I really don't want to cut it. If I just roll it around and make circles out of it without any kinks does anyone forsee any problems? My other question is my machine at work has limit swithes that are surrouded by a small rubber box, thats flat on top and slanted on both ends. It looks pretty durrable. I was wondering if anyone knows of somewhere to find something like that at? Thanks- Robbie

[jeffs555]

What kind of switches are they? What breakout board are you using?

[CNCRob]

Hey jeffs555,
Do you mean at home or at work?

[jeffs555]

I mean the one you were having problems with. The wires for limit switches can pick up noise, but they should not be that sensitive. Do you have them running along with the motor wires? Perhaps you are missing some pull-up resistors.

PS Kinks in the wires are not a problem electrically, except that the kinks put stress on the wires and they can break at the stress points. What is an electrical problem is bundling signal wires along with motor wires.

[Rance]

In addition, when you roll them up, you can create an electronic component called a coil. Like Jeff said, if these are adjacent to hight current wires (motor wires) the motor wires 'can' cause noise on the switch wires.

The other possibility would be that the switch could be inadvertantly coming on from vibration.

[CNCRob]

Thanks guys for your replies. I do have my limit switch wires run along with the servo wires (because thats the way K2 had installed them and I just left them that way). But I am pretty sure that wasn't the problem in this case, Because I never once had a problem with the limits before I added the 2 extra swiches, and still havn't had any problems since I unkinked the limit switch wires. Unkinking them may not have been the problem but I am unsure what it was. I bet I tried to home it 50 times last night and every time failed. Like I said in my other post I tried every thing I could think of to try to fix the problem. Finely I started to get worried that may I did something and missed something up when I installed the new switches. So I unhooked the y axis and tired it again, still no luck, then I unhooked the x-axis (it was now the same way it was when I purchased the machine) and it worked perfectly, Then I decided to hook the x-axis up for one last try and if it didn't work this time I was going to just unhook the extra limits and use it the way I used to have it with just one limit on the x , y, and z axis just for homing. When I hooked the x back up it worked perfectly. So then I thought I would try the y axis. I hooked it back up and it kelped missing up again. I thought for a moment about what could be the reason and happen to notice that when I had unhooked the x axis I had unkinked the wire. So then I unkinked the y axis the same way and hooked it back up. I tried it again with all of the limits hooked up and it worked perfectly ever since. This may not be the reason it started working but it was the only theory I could find. I am not sure what kind of breakout board it is, its the one K2 installed, but I will try to find out for you. I will also find the kind of switch it is, I have the name but I will have to look it up. Also since im not suppose to roll the cable, does anyone have any ideals what I can do with the extra cable? Thanks again- Robbie

[Rance]

I'd strongly suggest cutting it off to the appropriate length with just a smidgen of extra for slack. Of course I don't mind doing a little soldering either. I think you know your options if you don't want to solder.

Rance

PS: A smidgen IS a technical term that specifies just under 2 inches.

[CNCRob]

Thanks Rance, I may try cutting it to the right length. All that wire does is go from one limit to the other on each axis, so I don't think I would ever need much more than a little extra on each axis.

[CJL5585]

CNCRob:
Limit switches are wired in series. So, it could be that another switch is making causing the machine to think that it is at home position.

The wire length does NOT make a difference. This voltage is only low voltage and should not be a problem. It is also DC. A coil creates inductance with AC Voltage.

Check your switch wiring.

Jerry

[CNCRob]

Thanks Jerry, Ill keep that in mind if I have any more problems.

[unterhaus]

The fact that unkinking the wire solved your problem means that you have a broken wire or bad connection. You really should track it down, or you'll have intermittant faults. It may be broken insulation causing a short, which you should be able to find with an ohm meter.