Measuring linear displacement ( time )

hi,

Appreciate if anyone could point me to a sensor that could calculate the timing using colored tags ( or stickers ). Let me explain the scenario

There is this linear actuator ( that keeps moving in left <-> right ( both directions, left to right and right to left ). The displacement is about 1 meter. I would want to calculate the timing when it starts to move and when it reaches the end.

I can do this by using some magnetic proximity sensor ... and have 2 little pieces of metal and read the sensors , then calculate the time. Or I could have something that tells me the timing between reading 2 different tags or something? I could perhaps stick 2 different color stickers at either ends of the shaft that moves to and forth, and then use a sensor that say detects the timing between black sticker and a white? In short I want to know when the shaft started moving and when it stopped. I want this in milliseconds or something. Thanks

Cheers,
RW

ripplingwater75

Posts: 35
Joined: Sat Jul 01, 2017 8:45 am

Re: Measuring linear displacement ( time )

There are a number of approaches:

Mount limit switches at the extremes of travel.

Mount a small magnet to the end of the shaft and place hall-effect sensors at the two extremes of travel.

Mount a light sensor to the end of the shaft and have reflective targets at the two extremes of travel.

Mount break-beam sensors to intersect the path of the shaft at the two extremes of travel

Mount an accelerometer to the end of the shaft to detect the acceleration changes at the start and stop of motion.

Posts: 70448
Joined: Sat Feb 07, 2009 10:11 am

Re: Measuring linear displacement ( time )

hi,

Thanks a lot for the pointers. I was wondering if there is a board that can do this because the "super tiny" processor that I use for the other stuff is fully occupied with do some other sensing. So I was thinking if there is a little board with some light/color/IR sensor that can use come colored tags/stickers and do the same. Having a breakout board, or even having a separate micro-controller solely for doing the timing calculation would be great. Thanks once again. Really appreciate the pointers.

Cheers,
RW

ripplingwater75

Posts: 35
Joined: Sat Jul 01, 2017 8:45 am

Re: Measuring linear displacement ( time )

The closest we have to a one-board solution is probably the CircuitPlaygroundExpress: https://www.adafruit.com/product/3333
In addition to an M0 microcontroller, it has a number of on-board sensors that might work for you including:
* Light sensor
* Accelerometer
* IR proximity sensor

Posts: 70448
Joined: Sat Feb 07, 2009 10:11 am

Re: Measuring linear displacement ( time )

Alrighty, sounds cool. I'll try the Circuit Playground Express :) Thanks a lot

Cheers,
RW

ripplingwater75

Posts: 35
Joined: Sat Jul 01, 2017 8:45 am