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>
im newbie to electronics and want to learn. this project suites me as it seems easy to be done and i need distance meter that can be logged. <br> <br>if build this, do i need the oscilloscope? is all component typical so i can use your constant (Normalize_constant, etc)?
Hey, you don't need an oscilloscope to do this project at all fortunately though one would definitely help to debug it. With hope, if you follow the build instructions directly, it should fully work! All of the component values will work with the current values.
Very good Instructable!!!
Awesome instructable!!
Thank you :D
Very cool. Definitely one of my favorites.
Thanks a bunch!
Thats fabulous...
Thanks! :)
Is Technical but is a Nice instructable <br>i'm try to make the same with 38KHz carrier for decoding RC5 ir code and drive my futur robot <br>Thank You
Hey, the receiver section could be modified to work as a 38KHz reciever, I'm not too knowledgeable on the RC5 coding scheme, though wikipedia does a pretty good job of describing it, with an IR reciever and a logic analyzer, I think you could be onto a start atleast!
Hi <br>Very good teaching of the electronic of IR sensors <br>and also very good for my money <br>Thank You very much :=) <br>
Glad you liked it dude!
Cool rangefinder Pyrohaz.
Glad you like it! :)
Great Instructable. How accurate do you think this is? <br>
Hey, thanks a lot! :) Unfortunately, not particularly. As you can see in the schematic diagram, it uses lots of resistors and capacitors (none of these being particularly accurate, generally +/- 10%) which are also affected by temperature, humidity, extraneous light and pressure changes. If you were to keep environmental changes constant though, it could actually be quite accurate. Good enough for a not too important task though!
Cheers :D
Superb instructable , deserves a vote :)
Thanks dude! :)
Favoriting this. Could be useful on a mini-sumo robot -- it would be very nice to have a single circuit board with microcontroller and rangefinders integrated.
Cheers dude! If you only need it for short range, I wreckon thats a good shout! Cheers :)

About This Instructable




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