View Full Version : Troubleshooting Prox Switch

07-25-2003, 11:36 PM

I'm trying to get the shopbot up and running. I have tested the x, y and z axis motors. All's fine. I tested the y-axis prox switch and it worked fine. Tested the x-axis and it didn't stop the movement. I went back and slowly jogged the y-car over the target, the prox switch light comes on but the input signal didn't indicate the switch was open on the monitor screen.

I opened up the control box and insured the wires were tightly attached to the block. What should I do next to trouble shoot the prox switch? If there was a bad wire, the prox switch wouldn't light up when it was over the target, right?

I look forward to your thoughts.


07-26-2003, 06:21 AM
Resistance of switch changes on "trip". I might suspect wiring. If you don't have an "Ohm meter", you could "switch axis" to test for this.

It could be "Only" the return wire of the three broken.

I don't think my leads will stretch that far or I'd loan you my meter and probes...


B Imschweiler
07-26-2003, 10:14 PM
Make sure your control box and ShopBot are grounded. I had the same problem myself

07-27-2003, 09:59 PM
I have an ohm meter. I do have the bot grounded but will double check it.


07-27-2003, 11:47 PM

You should be able to take the lead going to the control box and "false trip" it with a piece of iron or magnet. The meter should show a change in resistance, the signal to the control box.

Some "Hall effect" switches trip "high to low" others trip "low to high". I don't know what switches you have. I have some I got surplus and don't know which way they trip.

Either way, it is a "wire chase". They can be quite frustrating - good luck.


07-28-2003, 01:55 AM
As everybody knows, I am an oddball for not having proxies on my SB
, but I do work with them often.

- Make sure that they are receiving the correct voltage power supply. Markings on proxy, loose connections, bad ground path, etc.
- Light on the proxy should change when you bring the tip of a screwdriver near to the tip of the proxy. If your power supply is good, and the light does not change, disconnect the 3rd wire from the SB's sense inputs and try again. (sometimes the 3rd wire is shorted to ground or to a supply). (Apparently, Chris is okay here). Generally, if the proxy light goes on and off, the proxy is healthy and the fault is elsewhere.
- You are lucky to have one working proxy out of two. Swap over the wires from the proxies (to the wrong channels). Triggering with a screwdriver, see if the indicators on the screen swap over.

07-28-2003, 07:40 AM
Okay, I've gotcha. Since the prox switch is lighting up when it's over the target, I'd figure that it's not shorted to ground or supply. Then I'll swap input channels with another prox switch and see if it works.

If that's the case, wouldn't I deduce that the issue is on the board? Heck, I'll get Timm to work on this, he's the electrical expert.....Good to have a brother that's an Industrial Maintenance Engineer.

Thank you all for your help. Regardless of this issue, I'm gonna try and find time today to check for square and get this thing working for a living!



07-28-2003, 10:49 PM

It appears that one of the wires coming off the prox switch has been damaged. We haven't found out where yet. At first I thought that we had it figured out because it looked like the previous owners had inserted two wires into the wrong channel. Green/sheild was correct, red was correct but there are two brown wires and one black wire. The black wire was in #3 but the two brown were in #4. And according to the manual, there should only be green/sheild, red and black. So, I tried putting the 2 brown and one black into #3.

Why do I have 2 brown wires instead of black wires?

I'll try and check the other things next.


07-29-2003, 03:06 AM
Wire colors coming off proxies have only been standardised recently - before that, it was a nightmare. This is the standard system today:


07-29-2003, 09:46 PM

Thanks for the diagram! But this brings up another question. Are the wires from the prox switches changed to a different wire harness? In other words, how does the brown and blue wires correlate to the green and red wires that are going into the control box?

Thanks for putting up with me.


07-30-2003, 12:33 AM
Sorry, gotta speak.
The colour coding of "brown, black, blue" is a European standard for wire designation. The "red, green" colour scheme is a North American colour scheme. The electricity doesn't care about the colour of the wire, but the important thing to do is to make sure the function (+), (-), or (input/load) of the switch and of the SB controller match up.

07-30-2003, 01:24 AM
No need to apologise for speaking up, Perry - wish you would do it more often. When Chris mentioned brown/black/green/red wires I thought that he might have a mix of proxies, then I checked a couple of American websites and could only find the brown/black/blue mentioned. And I also assume that we are talking of 3-wire proxies as opposed to 2-wire proxies. This thing can get quite messy if one doesn't have the proxy data sheets and you don't know if there is a color change inside a harness.......

07-30-2003, 08:13 AM
Gee, I have some proximity switches with Red, Black, White???

For some reason I don't think there is a standard.

08-19-2003, 01:04 AM

I got the x-axis prox switch working. It was a damaged wire where it comes over the car. It was probably damaged during transport.

I was going to surface the spoilboard and while looking at the spindle as it passed by, I noticed the cooling fan wasn't running! (Columbo). Geez, had to shut it down until I find out what the heck it's doing. It worked before transport. It's probably something simple.