Artcile on IR distance measurement

[languer]

You may want to look at Parallax's Robotics with the Boe-Bot (student guide), chapter 8.

Chapter 8: Robot Control with Distance Detection
In Chapter 7, we used the infrared sensors to detect whether an object is in the Boe-Bot’s way without actually touching it. Wouldn’t it be nice to also know how far away the object is? This is usually a task for sonar, which sends a pulse of sound out and records how long it takes for the echo to come back. The time it takes for the echo to come back can then be used to calculate how far away the object is. There is, however, a way to accomplish distance detection with the very same circuit you used in the previous chapter.

[ardhuru]

Perfect!

Between the 2 pointers you've given I should be able to figure out something.

Thank you so much!

Regards

Anand

[Ioannis]

For liquids you mayuse Ultrasonics too.

Ioannis

[Bruce]

Sonar would be a lot better option if you're trying to determine distance between the waters surface and sensor.

A really cheap option is to attach a float to a shaft, and attach the other end of the shaft to a potentiometer. Water level can be determined by an A/D reading from the pot.

[ardhuru]

Sure, Ioannis, Bruce, sonar would be great. But I'm apprehensive about the longevity of the sensor in the damp humid ambiance this application is likely to subject the sensor to.

Actually, I'd started a thread some time back specifically to do with measuring the level of water in a container.

A lot of great suggestions got thrown in. I'm afraid this thread is turning out to be an extension of that.

I had a fair degree of success with a resistor ladder, with stainless steel screws at the nodes being exposed to water.

Also toyed with the idea of a 'smart' sensor; a pic epoxied at one end of a tube with 10 inputs dipped in the tank, sending the data serially to the control unit, and operating on phantom power.

However, if it can be improved any further, I'd love that. And hence the query on IR.

Bruce, the float driven pot might not be very convenient as the depth of different installations varies. And the mechanical jugglery involved in customizing each installation is daunting.

Till then, if anyone's interested in any specifics, just so that they dont re-invent the wheel, please feel free to ask.

Regards,

Anand

[Bruce]

Hi Anand,

If this is for commercial application, they make sonar tank level sensors specifically designed to operate in wet environments. I mentioned this alternative since I've installed a ton of these in large water tanks for the state.

The pot + float thing I built one day for my own water tank in my sprinkler system. The float switches I had been using cost around 30-bucks each, and seem to be designed to self-destruct after about 1 year in operation...

My cobbled-together one has lasted 5+ years, and cost me around $3.

I've never tried reflecting IR off the waters surface, but I might have to try it some day. If it does work, I'm curious if maybe some of the Sharp IR distance measuring modules would be something to look at?

The only draw-backs I see with IR in this environment would be lens fogging or specular reflections from the water surface from ambient light.

[Tobias]

Back to the IR, I use this sensor quite often and it works great. Pretty cheap too. The output isn't linear though if it matters to you.

http://www.acroname.com/robotics/par...P2Y0A02YK.html