Help with taking pictures due to high change in wave impact pressure.

Hi,

I am currently in my final year studying Civil Engineering at university and after research into my dissertation last year on ''The effect of barrier shape on impact pressure experienced on the seawall (by wave action)'' there was an issue that may be improved with the help of Arduino.

To outline the bases of the experiment there were,

A wave flume (2800mm long, 680mm height and 300mm in width)
A wave machine
A seawall
Four pressure transducers located along the middle of the seawall (measures the change in voltage when a wave hits the wall)
A slow motion camera

The pressure transducers recorded voltage (PSI) which was then later on converted into Pressure (kPa).

The transducers are connected to a computer and by using a software called LabVIEW, the pressure is logged (data logger) in the form of an excel spreadsheet.

The slow motion camera recorded the 4 seconds of wave action.

The issue that I found was that it was hard to capture the image of when the impact pressures was at its highest.

I was wondering if anyone could give me any advice in connecting an Arduino set to the computer and a camera. When the voltage changes dramatically over a short period of time (wave impact) the camera takes a picture at that moment.

I am new to Arduino so any help would be appreciated,

Thank you,

Ruari

Do you have a camera in mind? I'm thinking it will be easiest to interface to an SLR camera which has an external trigger input. Often a 2.5mm "stereo" or "tip ring sleeve" jack.

Do you expect to connect the Arduino directly to the pressure sensors or are you expecting Labview to talk to the Arduino?

I would start with trying an up/down counter scheme. As the wave front travels down the trough it impinges on the first position transducer (perhaps a conductive pin) and starts a counter. At the second position sensor it stops the count and then counts down to zero and triggers the camera. If the sensors are equidistant from each other and the wall you should just capture the wave front as it impinges on the wall.

You could handle this quite well using the Arduino millis function, and you could adjust with software any “tweaks” needed in the count or even handle acceleration or deceleration of the wave front using a third position sensor.

RJ_Skinner:
The issue that I found was that it was hard to capture the image of when the impact pressures was at its highest.

This is quite impossible, in fact. This as you can not tell the future: you don't know if your rising signal has reached the top, or just has a minor deviation making it look like it levels off before continuing. I expect your signal to be quite noisy with all that water action, making it all the harder.

You have your slow motion camera, why not use that? The moment you sense the wave coming in (pressure increases) switch on that camera, log the pressures of the following four seconds, later determine when the peak was and which frame of your video was recoredt the closest to that point in time.