Instructables

How to measure the displacement of a gravel particle by arduino kit ans extensometer sensor?

I want to measure the displacement of a particle of gravel in the surface of an slope, along the year (each hour ot forur hours or something like that), in order to study the erosion evolution of the terrain. I suposse that the use of an arduino kit (with sd or micro sd datalogger among other characteristics) and some extesometer sensor could be the better option, but i don´t know how to do it... Thanks!

Grathio4 years ago
I think steveastrouk has it right. Hte only sensor that I know of that can easily detect something's position at a distance is a camera, so take a photo every day. You can automate this with an Arduino pretty easily if you have the right camera. (Or you can cut open a cheap used digital point-and-shoot camera to get at the trigger switch.)

To determine the movement paint a few particles a contrasting color, and put a few stakes or wire flags in the ground every meter (or whatever). These fixed indicators will let you measure the distance traveled.

Here is one project using an Arduino to trigger a camera.

Here is another. You can find more if you search for Arduino time lapse photography.

The ardunio's native clock isn't super accurate, over the course of a year it will drift and start taking photos at night. Either add areal time clock to your circuit or you could simply hack in a light detector so it would at least only take a photo during that day.
Hadn't thought of triggering a digital camera. Neat idea, if there is enough storage for what the OP wants.
Take a picture with a webcam every hour or so. I don't know if an Arduino can, but a Fox Board LX definitely can. Paint your particle white or somesuch and then watch it. Steve
madepablo (author)  steveastrouk4 years ago
Thanks so much for all your ideas. However, the idea of the digital camera it is not possible, because the weather conditions. i want to apply this experiment in Antarctica. I want to know the displacement due to the frozen/unfrozen processes under the winter snow. So only with an small extensometer (gauge) it should be possible. The camera require not snow-coverage of the site, what change the conditions.... Thanks!
Rather than waste my time, wouldn't it have been better to add ALL the conditions you are under ? Making an extensometer work in -50C will be interesting, and since its a contacting method rather problematic.
madepablo (author)  steveastrouk4 years ago
Thanks Steveastrouks, However, I was not trying to waste your time. In fact i was clear and i included all the necessary information. I asked for an extensometer to measure the movement of a particle of coarse sand or gravel, not a general method to measure the movement. In that case, the digital camera is a good method. But thanks so much for all your time and your efforts to reply my question. The temperature is not an important problem. There are comertial extensometers to work under that cold temperatures, and to protect the arduino component to not be frozen during all the year is also an easy problem to solve (such as other intruments that i already have working there). Kind regards,
I don't think there's a reasonable way to do what you want. "underneath snow" and "in arctic conditions" are very significant constraints for a project. Weather is important because there is just no simple sensor that can determine the position of something that accurately at a distance through snow. If I had unlimited resources I might make fake stones with RFID tags (and large antennas) inside and set a number of high power RFID readers around the area to triangulate the position of the movement of the fake rocks. However I'd be surprised if I could locate them with a precision better than 20-30cm. And that would cost many thousands of dollars even before they were hardened for the weather. Which might be tricky because the enclosures would have to be transparent to the RFID signals. However I suspect snow would block an RFID signal enough to be a problem. Water is notoriously good ad absorbing radio signals. And radio signals are literally the only thing you can use to track if you don't have line of sight.
Post some examples of the hardware. I don't see how you can follow a particle, under snow, without materially affecting the sample. Do you want watch a SINGLE particle ?