Here is my instructable on how to construct a pretty simple (for some!) short range infrared rangefinder/range sensor. Infrared rangefinders are very useful in a number of projects. The majority of these come from obstacle detection (in robots) or generally detecting distances! The one shown here is only a simple rangefinder and will only really be able to measure about 6 or 7cm infront of the range finder. Luckily, most objects reflect infrared well enough to produce a reading (including a hand, paper and tin foil). I will be showing you how to use the infrared range finder with an Arduino and ways of linearizing the result.

Step 1: Theory

The theory behind an infrared rangefinder is that pulsed infrared is emitted from an IR led and then reflected back off an object into an IR receiver. As light adheres to the inverse square law which states that as distance from a source is increased, the intensity decreases by the square (Source: http://hyperphysics.phy-astr.gsu.edu/hbase/vision/isql.html). Essentially, the light is emitted by the infrared LED, which then bounces off the object. In the first instance, the LED is the emitter and the reflective object is the observer. Once the light hits the object, it then bounces off and is reflected back to the IR receiver. The object is then acting as the source of light so the inverse square law takes effect twice. This has the problem that the maximum range of the rangefinder is quite short and to increase the range, higher power LED’s would be required.

Another problem that takes affect with light based rangefinders is how it can be affected by ambient light. I fix this in my rangefinder by modulating the emitting LED. Without this modulation, a simple light bulb connected to the mains can affect the result by superimposing 50Hz onto the actual signal.

My rangefinder works through having a  modulated IR source at an ultrasonic frequency, being detected by a IR receiver (IR photodiode) which is then fed into a high pass filter, amplified and peak detected.
I finally built your 36KHz version of the NE555 everything is OK thank you<br> Now I will look for RC5<br> everything is here smd pictures of test<br> <a href="http://sdrv.ms/QCZ8j1" rel="nofollow">http://sdrv.ms/QCZ8j1</a><br> <br> <br>
<p>Awesome pcb man! Glad it worked for you :)</p>
<p>Thats incredible</p>
<p>This is so great!</p>
<p>Its fascinating</p>
<p>Thats really good</p>
<p>Really good</p>
<p><br>Thats awesome...<br></p>
<p><br>Thats fabulous<br></p>
<p>Thats fascinating</p>
<p><br>Its helpful :)<br></p>
<p><br><br><br>Thats grand</p>
<p>Thats incredible<br><br></p>
<p><br>Thats spectacular...<br></p>
<p>Very nicely done! Having had to deal with Sharp this looks like a nice way to not have to use their stuff.</p><p>Question on Step 3 - probing the IR receiver - the scope trace. What point were you probing and what was your voltage scale on the scope?? I ask, as I am trying my hand at building up this circuit, having some issues with getting it working on the receiving end. The darlington pair doesn't seem to be amplifying the signal. Thanks!</p>
<p>her is the kicad PCB projet in zipped file in my i've remplaced the 4148</p><p>diodes by shottky diodes</p>
<p>thanks to :)</p><p>her is the kicad PCB projet in zipped file in my i've remplaced the 4148 </p><p>diodes by shottky diodes </p><p>http://sdrv.ms/1aJznbw</p>
<p>Them 3d plots are great! Is that a part of kicad? I'm still used to working with eagle haha</p>
<p>yes is part of kicad</p>
<p>Cheers! :)</p>
<p>Thank you!</p>
<p>Thanks :)</p>
<p>Cheers! :)</p>

About This Instructable




Bio: I'm a student from Cheshire, currently studying at University of Nottingham!
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