[rcpilot82]

I have just finished my router and was setting up the home/limit switches when I ran into this issue. first the setup; mach3 running on laptop w/parallel port. 3 axis router with hobbycnc kit. Now the issue, I find that with the steppers turned off the home/limit switches work fine. when the steppers are turned on the "leds" on the diagnostics display in mach start intermittenly flashing (as if a switch is being triggered) not allowing me to complete the setup of the switches. i am running shielded 20 gage wire, all switches are wired correctly (series) and I have even gone as far as soldering all the terminals together to no avail. I am stumped at this one and need help! any ideas?

[TOTALLYRC]

I have just finished my router and was setting up the home/limit switches when I ran into this issue. first the setup; mach3 running on laptop w/parallel port. 3 axis router with hobbycnc kit. Now the issue, I find that with the steppers turned off the home/limit switches work fine. when the steppers are turned on the "leds" on the diagnostics display in mach start intermittenly flashing (as if a switch is being triggered) not allowing me to complete the setup of the switches. i am running shielded 20 gage wire, all switches are wired correctly (series) and I have even gone as far as soldering all the terminals together to no avail. I am stumped at this one and need help! any ideas?

Make sure that the wire shield is grounded at the controller end only.

Also go into the general configuration page and increase the debounce setting. This will increase the time a signal has to be active before Mach will recognize it as valid.

Mike

[rcpilot82]

Make sure that the wire shield is grounded at the controller end only.

Also go into the general configuration page and increase the debounce setting. This will increase the time a signal has to be active before Mach will recognize it as valid.

Mike

Great ideas, didn't solve my issue though I ruled out the computer being a possibility by trying a desktop pc, same thing. I am sooooo close to cutting parts out on this thing but I really want the home/limit switches to work as i am a newb. any other suggestions?? I am all ears!

[wyldesyde007]

what type of switches are you using no/ nc? and how did you wire them? I used a cheapo radio shack push button switch that is a nc switch that way if a wire were to break or become mysteriously detached it would stop the machine. I used plain old speaker wire to connect them.

[wyldesyde007]

I did find that running my cnc from a laptop (which I did for a while before I built a dedicated pc for it) made it run slow, once I connected it to a desktop pc I had to re-tune the steppers as they were being run faster than when it was hooked to the laptop.

[wyldesyde007]

You might try connecting only 1 switch to the limit switch outs on your board then watch the diagnostic page in mach as you depress the switch and see if the light blinks on and off as you push it. If it does then you know the board is wired right and you may have a faulty switch, keep checking the switches 1 by 1.

[ger21]

Did you try around 5000 for the debounce?

[rcpilot82]

Thanks for the ideas guys, yeah I tried everything from 100 to 9999 on the debounce. switches are all NC and wired in series. with the steppers off I verifies that all the switches are operational, and verified this with a meter without the wires connected. I started out with just speaker hook up wire for the switches and then re-wired with the shielded wires after I discovered this. I now have a desktop pc hooked up to the router and same result. what now??

[woffler]

check with hobby cnc and see what they have to say as to the wiring of the switches some bo boards will only run home switches in the normally open position i know it sounds nuts but it depends on the board manufacturer.

[123CNC]

What type of limit switches? Optical, mechanical? If mechanical, are the plunger or arm-roller actuated? How close is your trip point or switch engagement when this occurs, or are you nowhere in the ballpark physically when this happens?

When you turn your steppers on do your limits on the diagnostics page flicker with the steppers at rest or during motion or both?

If you are seeing intermittent signals with steppers on at rest, how difficult to dismount your limit switches or just the wiring and move to a different orientation and monitor the flickering status (sweep that long antenna for poorer reception)? Are your limit switch wires ran side by side with your stepper drive wires or other power lines? Are your stepper motor leads shielded?

How and where did you terminate your limit switch shielding? Where is your panel or BOB ground in relationship to this point?

[rcpilot82]

Switches are mechanical,arm roller type. I am nowhere near the switch when the trips happen. Yes when the steppers are powered up the limits lights flicker, both at rest and in motion. I have relocated as much wire as posible and it makes no difference. all wires are shielded both stepper and switches. there is no BOB, all the connections are on teh hobby cnc pro board. here is something funny i noticed just now. I removed the wires from the y and z axis switches from the circuits and my stepper "hiss" went to about half of what it was so i cut the signal input wire on pin #11, result was broken circuit "duh" but stepper hiss went down a bit. when I removed the ground wire my stepper hiss went almost completely away!? how can the limit switches affect stepper hiss? another wierd observation was with ONLY the ground wire hooked up to the switches, when a switch is pressed the "tone" of the stepper hiss would change?? I am stumped

[Claude Boudreau]

I had a big problem when I first build my cnc router I was hearing an intermittent hiss in my stepper and loosing control of the current enough to burn board , solved the problem insulating the computer ground from my control box ground, with a simple piece of acrylic to mount the db25 connector.Before I did this when I connected the ground of the shield wire I heard noise in my motor. Someone explained to me that was due to induced voltage on V.ref line . Hope this help.

[123CNC]

I'm not familiar with the HobbyCNC line of products. I tried to find some more information from their website, but it doesn't appear or at least is unclear if there is any circuit isolation from the PC. Even with cheap PC's this makes me a little timid.

I'm not a big fan of unipolar drives just because of the hiss or sing. Although cost obviously makes them more attractive.

Also looking at their board does your driver power supply connect there in the middle? What type of power supply are you using regulated/unregulated, switching? Where is your power supplies reference to ground and where is it in physical relationship to you PC AC ground or your Pro board ground? Is your Pro board mounted in an enclosure?

[rcpilot82]

123cnc, look here for pics of my enclosure and setup; http://www.cnczone.com/forums/showth...t=53128&page=2
power comes in the middle of the board. I have a tx going to a rectifier, then a smoothing capacitor, and then to the board. let me know if you see anything.

[rcpilot82]

claude, this sounds similar to my issue, using the ground terminal for the switches on the board I had more "hiss" in the steppers. somethbing to look into, thanks.

[123CNC]

I quickly barreled through your build thread, reading a little and stopping to look at a few pics. The pics of your control cabinet that I saw, I could not see your main power line in and its ground (G - green wire, L - black, N - white). I didn't see any pics with your Pro board mounted and associated grounding.

Are you using a laptop or desktop or mounting a motherboard within the control cabinet? I thought I saw a parallel port cable in one pic of your Pro board, connected to desktop? Your cabinet looked as though some panels are plastic, the face, what about the side panels?

I didn't see any shield grounding either. I did see multiple blue cables out of the cabinet, are these Cat5 or similr, twisted pair?

How long are your stepper leads and how long are your limit switch leads? How short can you make them?

I agree with Claude in that it 'sounds' like a ground loop or EMI/RF problem. The line of questioning is just in effort to help you find the masked bandit.

[rcpilot82]

123cnc, I used the powercord provided with the hobbycnc kit. there was no ground wire. it comes in beside the capacitor. I was using a laptop but have switched to a desktop that is in it's own seperate tower. the entire case that the board is mounted in is metal except for the front trim and rubber feet. the cat 5 wire has been ermoved and in it's place is 20ga,4 pair shielded cable.(total of 8 wires and 5 grounds per bundle) I forgot I had the cat5 in those pics. due to the fact that my router is rather large and has a moving gantry my wire lengths are long, from about 4' for the x axis to about 22' for the z axis. I cannot make them much shorter without straining the wire. limit switches have similar lengths but the x axis is about 10' long. it's wierd that having an incomplete circuit (ex. only attaching the ground terminal for the switches) has a sudden effect on the whole works. I will answer as many questions as I can to figure this out, my collets and tooling are on the way!
here is an updated pic showing the current wire

[123CNC]

Many shielded cables like you have pictured have a foil layer and a bare multi-strand conductor. In the pictures I can't make out how the shield is terminated. You should try to keep shielding as close to the final termination as is reasonable, allowing for unstrained connections. If the single ground point for your control cabinet is very close to these terminal connections you could just run the bare multistrand to the ground lug. If the ground point is some distance or running across or close to other connections, it would be better to use insulated wire to connect the shield to your ground point. You will also want to replace your main power leads with a three conductor cable with a grounded plug (NEMA 5-15). Your current configuration would be considered unsafe in that any stray current has no where to go.

I can't find any documentation for the Hobby CNC Pro board, I'm amazed youv'e gotten this far.

It looks like you've got screws through the board into your control chassis. It is unclear if you have any stand-offs, metal or plastic, is this an intentional or unintentional ground point for the board?

You also have extremely long wire runs to your motors and limit switches making it more susceptible to noise. How straight are these runs. Do they cross each other or make any u-turns or loops?

The board information indicated 10K pullup resistors on the limit connections. However I can't distinguish in your pictures how the limit switches are wired. Do you have three independent limits, 6 wires connected to the board and three shield drains? Or are the limits ganged in series, one wire running out and around through each switch and coming back to the input? What is the source signal level for the limit switch, 5Vdc? Low voltage signals are more susceptible to spurious stray current, either radiated or conducted.

Perhaps some Hobby CNC board user can give you more insight into the intent of the connections and operation of your installation as it pertains to the board.

Getting your grounding and shields straighten out may help, but your long runs could still prove difficult and may set you apart from other users. Meaning, just because others may tell you they have had great luck even ungrounded, doesn't mean you should be just as lucky.

Another consideration, your gantry is all aluminum (looks great by the way), you may want to double check and make sure you have no continuity between your limit wiring and the frame. Check both the signal wires and the shield.

[neilw20]

If a piece of wire (or shield) is terminated at ONE END ONLY, then no current can flow through it. Actually small amounts can flow due to capacitance but this will usually not be significant in this environment.

Keep signal (limit switch, sensors, encoder) wiring well away from stepper motor wires and always try to rout them at right angles to each other, and never tied together in the same bundle.

Just because you have a negative terminal nearby don't use it instead of running a wire back to the common negative.

Single points for negative power.
Single points for positive power.

Never use the 'nearest' common of a conductor. This is important if significant current flow is concerned.

Consider every wire as a resistor. Analyze what currents flow, and
don't allow currents to flow in ANY of you earth conductors.

That's a start any way...
It easy to get the smoke out. Hard to get it back in again.

My 1000th post. Cool.. :withstupi

[rcpilot82]

ok, well I am back at it today and here is what I have done, I changed the 2prong power cord to a 3 prong shielded wire and grounded it. shortened up some of my wires and took all of the stepper cables and twisted them together and grounded them as well to the case. I also removed the screws from the board and used zip ties to make sure the board has no way of electrically getting to anything else. when I jumper the hobby cnc board pins for the switches, it works fine, no extra hiss in the steppers or anything. but when I hook up my switches it goes back to the same old bs. Could my switches be the problem? here are some pics.