Specifically, I am trying to detect whether an umbilical boom from fueling a rocket has retracted, and other miscellaneous tasks (vents raised / retracted).

I have done some research and have found ways to determine the displacement of an object - is that actually to be the best way to do it? For example, say the boom needs to retract 10 ft. In that case, if the sensor finds a displacement of 10 ft +- 10%, then MovementStatus = True.

Or is there some form of light sensor / position sensor that just detects the fact that the object is in the position where it's supposed to be, in an efficient way?


2 Answers 2


I would keep it simple and use a microswitch to detect the end position:

enter image description here

and connect it to your Vcc. Add a pull-down resistor to ground, and you get a logic level indicating the status: high = switch closed, low = switch open.

  • 1
    \$\begingroup\$ and.......... ? \$\endgroup\$
    – markrages
    Commented Sep 14, 2012 at 17:13
  • 1
    \$\begingroup\$ @markrages - building up suspense :-) \$\endgroup\$
    – stevenvh
    Commented Sep 14, 2012 at 17:42
  • \$\begingroup\$ classic stevenvh, never mind. \$\endgroup\$ Commented Sep 14, 2012 at 18:53
  • \$\begingroup\$ Wow, they're big, aren't they? ;-) \$\endgroup\$
    – m.Alin
    Commented Sep 15, 2012 at 19:20
  • \$\begingroup\$ @m.alin - haha, you remembered that! :-) Actually, these don't show that much bigger than real size on my 21" monitor. The "micro" seems to be compared to those huge industrial switches, often 10 cm or so. Maybe you're looking at them on a 250 cm TV screen? :-) ( BTW, I went to have a look at that post again, but as I remembered it the original image was *way bigger, but I didn't find that in the edit history :-/ ??)* \$\endgroup\$
    – stevenvh
    Commented Sep 16, 2012 at 6:19

Usually microswitches are used to verify that a piece of equipment has reached a particular position. They come in many configurations; the actuator can be a simple spring leaf, or it might have additional features such as a roller that drops into a detent on a moving part.


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