Additional Pins for Limit Switches

Support Motor controllers/drivers and motors
1

I have an analog joystick attached to a TIC834 along with serial control. I am using SDA,SCL,TX and RX. I can configure the RC pin for one of my 2 endstops but of course I need one at each end.
I can do this from program control but it would be nice to use the TIC feature. Is there a way to rob another pin for this purpose.
thanks
Fritz

2

Hello.

While it is not our recommended method, you could use the Tic’s 5V pin as the high source of for potentiometer and then use the SCL pin for a second limit switch.

Alternatively, if your serial device is capable of reading the potentiometer, you could try using that to read your analog input directly and map it to set target serial commands.

Brandon

3

Thanks Brandon…
I already have some code aligned to option 2, but I lose the automated features of the limit switches (e.g. turning off the motor in one-direction until the switch is resolved). I could write the code but I like your first option better. Not sure why you do not recommend picking up the 5V from the TIC? I can certainly pick up 5V regulated elsewhere from the processor for example. (I probably will use an arduino or Nvidia here).
I can tolerate some small changes in the 5V due to load if they exist. I am simply driving the motor to turn a lead-screw. I go to a smaller stepsize when the joystick is at less than about 30deg travel but speed control is not critical.
I will give this a try tomorrow

thanks
Fritz

4

To clarify, the alternative option I was suggesting was to read the potentiometer input from your serial device, and still let the Tic handle the limit switches. In case there was some confusion, the limit switch functionality will still work the same way when controlling the Tic through serial; please let me know if there was something in our documentation that made you think otherwise.

You can use the Tic’s 5V output for the high side of the potentiometer instead (or supply 5V from another source like you mentioned), but that way you do not get the benefit of the inline protection resistor on SCL. You can find more information in the “Setting up analog position control” section of the Tic user’s guide.

Brandon

5

Thanks Brandon.
“read the potentiometer–from serial”. Yes. I had done this.
“still work the same way” Yes. Same as above. Your doc is fine (decent).
I am mounting all these on a circuit board so I can always add protection there.

One question–what is the ON/OFF voltages for your sensor?

Thanks
Fritz

6

Can you clarify what sensor you are referring to?

Brandon

7

Whoops–sorry. I accidently cut off a paste for this—.
I am putting limit sensors on both ends of the system ( a stepper motor driving a threaded shaft). The limit sensors are not mine-they are optical and not 0V/5V.
So on your TIC834, what is the on/off voltages of the limit circuit?

thanks-Fritz

8

An input voltage of 2.1V on SCL and RC will be read as a high signal. If you are still unsure if your optical sensors will work, you can post more information about sensors (such as a link to a product page or datasheet), and I would be happy to take a look.

Brandon

9

Thanks. I am using SteppersOnline sensors here but hold tight while I look into this. The assembly left my lab and is at a colleague’s place now so I will check with him.
Your support is greatly appreciated.
Fritz