15 Dec 2011

Build your own IR detector

Let's have a look at the result!

Check our my last tutorial to see how it works (theory and example).

first of all, test all the components make sure they work!

Let's do some calculations, and design the circuit, Here is my Schematic:

build it on the strip board... This took me 3 hours!! but I am getting better at it ; ) i can tell.

The whole thing costs me:

8 x tcrt5000 = £3.4
1 x strip board = £1
Terminals = £0.5
1 x BJT = £0.5
Resistors and wires = £ 1

Total about £6.

When I finished and testing, realised R6 - R9 are too small, (voltage at the collectors of the phototransistors are too small), I decided to take the 4.7k resistors off and replaced with 22k. but it doesn't seem to improve a lot...

This is what I got at the end.

The range isn't as good as I expected, it's probably the size and ratings of the LEDs (3mm), however I have ordered some 5mm, and I will probably use more LEDs to try to improve it, but this is good enough to be used for obstacle avoiding.