Artcile on IR distance measurement

[ardhuru]

Hi everyone, I realize this sounds vague, with very sketchy details, so please bear with me.

Somewhere a long time ago, I'd seen an article on a technique to measure the distance to an obstacle using IR; it was to do with either pic basic or the Stamp, I just can recollect.

Basically, it described a technique wherein you use just one source, and one detector (3 pin demodulator). You begin by modulating the transmitter at its optimum frequency (38 KHz?) and keep transmitting a single character, and keep reading the pings. You then keep reducing the modulation frequency till reliable pings stop. The difference between the ideal frequency and the one at which you no more get a ping would then be a function of the distance.

No amount of Googling has yielded any success.

Does anybody remember this at all?

Would be great if someone has a copy, or a vector to this, folks.

Thanks,

Anand Dhuru

[mackrackit]

This might be it. Good for 6 inches.
http://rentron.com/PicBasic/infrared..._detection.htm

[ardhuru]

Boy, that was it, and that was fast, Dave!

Thanks so much.

I thought I had pretty much most of Bruce's articles Scrapbooked in my Firefox, but somehow this one I did not.

Now to see if this range can be increased to a couple of feet. Might not be difficult since the whole environment, including the reflector can be in a tube, isolated from the ambient. Yup, thats right, my quest for the 'perfect' liquid level detector continues.

Thanks again.

Regards,

Anand

[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