How to write LabView Code to avoid Limit Switches

[ramdas369rd]

I'm self-learning LabVIEW and i'm developing a linear actuator of size 50x50mm. I couldn't find a miniature limit switch to place inside this size. Most of them are sized around 28mm i need to place at least 2 limit switch. So if i place the 28mm limit switch there won't be any room left for the linear motion. So i'm thinking about if i can avoid limit switches and use a code instead of it. If the stepper motor knows when to cut off then we can avoid limit switches, i guess. Could anyone think that it's possible?

[RavensFan]

A software solution is not necessarily a safer or more reliable method over a hardware solution.  What is the danger if the software fails to do its job of stopping the stepper motor?

What features do you have that would let the software know where the actuator is along its limits of travel?

[RTSLVU]

Limit switches are a safety device so, I guess the main question is:

What happens if the actuator is moved beyond its limits?

If the answer is: It could possibly, ruin the product, break the actuator, or cause injury to a person then you need to find a hardware solution.

I am sure there is a way to keep track of how far you have moved the actuator, a Linear Encoder comes to mind, (I mean you are going to have to know how far you are extending it anyway, aren't you?) and stop it before you reach the ends. 

[altenbach]

I am sure that there are much smaller solutions available. Since you say 50x50mm, is this a 2D stage? is 50mm the range of motion or some overall size design limit (i.e. does it need to fit in a tight location).

Can you show us a picture so we get a better idea.

This is a hardware problem, not really a LabVIEW problem.

[ramdas369rd]

50x50mm is the size of the body, a stepper motor is connected outside the body and a lead screw of size 50mm comes at the center and profile rail at both ends moves the top portion of the body linearly. So far without the limit switches, i achieved a linear motion of length 35mm. It is way more than what i need to achieve which is kinda good. I need to achieve +26mm but if i'm placing limit switches inside the 50x50mm body the top plate can only move around 10-15mm.

[ramdas369rd]

Yeah you are right, right now i build my own limit switches which i can fit inside the body. But i prefer to stick to the industrial standard products which are available in the market. I know this is a NI forum but is there any chance that you know about micro limit switches or any other device which can do the same function. 

[AnalogKid2DigitalMan]

Any option to mount external opto-interrupter 'flags' to the stage and add optical pass through (emitter + detector) sensors instead of mechanical limit switches?

-AK2DM

[ramdas369rd]

Yeah its also a good option but the problem is the size of the available product is not suitable to fit inside the structure. 

[ramdas369rd · Accepted solution]

Managed to fit a 20mm length limit switch inside the structure by redesigning the limit switch lever, thus by getting a good travel range between 2 limit switches. Theoretically, it should work.