Limit Switch Issues

[Tweakie.CNC]

Before admitting total defeat the one thing I would try is…

Connect +24V to the I 10+
Connect the n.c. limit switch in series between 0V and I 10-
(obviously the same 24V power supply has also to be connected to the UCSB)
Change the I/O logic state of Pin10 accordingly and make sure you have set the Port correctly.

Worth a try ?

Tweakie.

[dezsoe]

The results were the same. The controller is not recognizing the input signal from the limit switch when it goes from 24 volts to 0.7 volts. The corresponding LED on the UCSB does not light up or go out when the limit switch is triggered.

So, you could not light up the input LED. Well, if you have no input signal then this "$4000 piece of junk" has no signal to show on the screen and/or use as a home/limit signal. First check the logic power on the UCSB: does the LP2 LED light? If not then you may have a bad connection between the UC300ETH_5LPT and the UCSB. Check or replace the 26 wire cable.

[fsli]

The corresponding LED on the UCSB does not light up or go out when the limit switch is triggered.

This is why it's so important to understand the devices you're working with before trying to wire them into a CNC machine, and why it's so critical that you make sure the hardware is telling you it's alive before screaming about faulty software.

The documentation for the UCSB shows all the LEDs that are on the board, and describes the information relayed by each of them.

1. Confirm you have +24v power arriving at the UCSB on the DCin power terminals, and that the LP1 light is lit.
2. Confirm that you have +5v power available on the DCout terminals, and that the LP2 light is lit.

If you don't have power at those places, and those LEDs are not lit, then your UCSB will not respond to anything. Once you get proper power indications, then go back and directly connect +24v to I10+ and connect I10- directly to the common ground point. That should light up the LED for I10 (LI 10 on the above image). If it doesn't then you have a failure of the input terminal. If it lights up with power directly connected, then you can reconnect your switch and again confirm the I10 LED is lit when the switch is closed, and it extinguishes when the switch is open.

As I stated yesterday, ignore everything in the software until you get the hardware LED indications behaving correctly.

[BertZ]

I wish to thank everyone who contributed to this thread. You all played a role in finally solving this issue.

In addition I want to apologize for my rants. There was no need and it was just my frustration spilling over.

Now to the solution to the problem. I went back and studied the manual and realized that the onboard 5V supply was strictly for use with the output terminals. The 5V logic power is supplied through the 26 conductor IDC ribbon cable. I should have realized the problem immediately when I changed UCSB boards and I still did not have LP2 lit. I went back to work and made a new IDC cable and plugged in between the BOB and controller. Bingo! The limit switches work as they should and the machine homes as commanded.

I am sure other issues will pop up but we can consider this case closed!