Tic36v4 Forward Limit Switch Issues

I am using a Tic 36V4 stepper controller and having some trouble with the forward limit switch. I have a kill switch on SCL, and the Reverse limit switch on TX (right now). I have tried the forward limit swatch on TX, RX, and SDA and get the same results in all cases.

The motor goes backward without any issues and stops at the limit switch.

The forward limit switch registers just fine on the Tic Control Center.

When the motor is moving forward it does not accelerate smoothly. It never reach anything near full velocity. If you watch the limit switch marker you can see it flash yellow very briefly.

When I disable the limit switch (in software) the motor behaves properly in both directions.

It is not a problem with the switch. (Changed that. Shorted the wires. Removed the switch and set to active low)

Any assistance would be appreciated.

You might put a meter on the switch wires and see what kind of voltages you’re getting, make sure it’s either 5v or 0v. I was getting something similar last week using an optical switch, and discovered it was only returning 3v or so. Installing a pullup resistor cleaned things up nicely.

Thanks for the input. That would certainly explain the erratic behavior but in this case I have the singles active high, and grounded when the motor is operating normally and thus pulled up when the switch is tripped.

I put a scope on the line to see. Really clean with the motor is not running. Very noisy when the motor is running (no real surprise here). But the signal in stays clean a around 20 mV so unfortunately not the cause of the problem.

I have two Tic 36V4 boards. Same issue on both boards.


I moved your thread to the “Motor controllers/drivers and motors” section of the forum since it seemed more appropriate.

Could you post pictures of your setup that show all of your connections? Additionally, can you post a copy of your Tic settings file? You can save a copy of your settings file from the “File” drop-down menu of the Tic Control Center while the controller is connected.

Also, you mentioned a kill switch, forward limit switch, and reverse limit switch; can you clarify if you are using all of them at the same time? If so, when you say it works fine when you “disable the limit switch”, which one are you referring to?


Attached is a picture of the actual setup, the schematic, and the Tic-configuration file.

The kill switch is located just below the 36v4. When installed the physical device will be quite separated from the control computer so this provides a way to shutdown the motor when doing installation and adjustments.

The system uses a forward limit switch, reverse limit switch and a kill switch all at the same time. My software homes against both switches to determine the number of counts along the track. This allows using the limit switches to define the travel (about 30" in this system). Have hard switches also provides some safety against code errors.

I only have an issue with the forward limit switch. If I disable the forward limit switch in the Tic control center then I have no issues (also no forward limit switch).

tic_settings.txt (1.5 KB)

Thank you for the additional information. The Tic 36v4 has a maximum operating voltage of 50V, and your wiring diagram shows a 48V supply. 2V is not a very big margin, so you might try scoping your supply voltage to see how steady it is while the system is running. What are you using as a power supply? If it is a battery, the fully-charged voltage will almost certainly be higher than the 50V maximum for the Tic 36v4.

When you say you can see the limit switch marker flash yellow briefly when it is running, are you referring to the “Limit switches active:” indicator in the “Status” tab of the Tic Control Center showing that the forward limit switch is being triggered? Could you post the scope captures you mentioned of that line while the motor is running?

If your limit switch wires are running close to your motor or power wires, you might try separating them as much as possible.

Also, it looks like you are using metal standoffs and a metal plate, so you might double check that nothing is shorting.


Thanks for the input. The supply is an Agelent bench supply. Really well regulated. I actually turned it down to 40 V, but that did not make any difference.

I am attaching a video of the Tic Control Center when the motor is moving forward. Early in the video you can see the yellow forward limit trip, but the switch is grounded.

I attached traces of the switch closed and open. For open with the motor running it is necessary to change the controller so that the limit switch is not active.

The wires are close (2-3 inches but not super close). The board is on aluminum standoffs but there are nylon washers under the board to make sure it does not short out.


20210615_165246.mkv (4.6 MB)


Thank you for all the help.

Found the problem. Basically noise pickup on the line. The wires were about 2" apart, but I had to move them about 6" part and even then they crossed over each other at one point so that had to be removed. Once they were far enough apart the problem went away.


That is a fair amount of noise. I’m glad you were able to get it working by separating the lines! Thank you for letting us know.