Assemble and Programming Sensor Color

After my last article that discusses the basic concepts of color sensor, will now be discussed on how to assemble itself and to program a simple color sensor. To detect the number of colors. All it takes is a single LED and a sensor detector sensors like infrared transmitter, can be seen in the figure LED LED nodes and black (which is actually the phototransistor).

Photo Transistor

If desired photoresistor is used as in the picture then use a green LED with a photoresistor which was given a protective black solasi.

Photoresistor

One advantage of using a bright LED for sensing robot is a robot can see very clearly when the light dies. Here are pictures taken from societyofrobots where the robot uses sensors to detect the line color.

Color Sensor Pikachu

And if we want three different colors, we can assemble as shown below.

three color

Programming is relatively simple color sensor. We can simply turn on the LED through the digital output pin, wait for 50ms to photoresistor change (photoresistor has a slower response than the infrared sensor) readings analogues - after it shut down again the LED (if owned more than one LED)
For example if the robot we have three different LED colors here are algorithms

    Turn on Green LED
    wait 50ms
    record the sensor readings G
    Green LED off

    Red LED Light
    wait 50ms
    record the sensor readings R
    Turn off the Red LED

    Blue LED Light
    wait 50ms
    record the sensor readings B
    turn off the blue LEDAnd now, by combining the similarity matching algorithm in the previous article by the pre-calibration, the robot will be able to identify the target.
Detection distance with shadows
What is the difference between a bright green with dark green? The difference lies only in bright green has more electromagnetic waves that can be detected and / or transmitted. For example, imagine that we have a green apple and our robot measuring green color. Then we move the apple one inch back and then perform color measurement again. What will happen? The answer is simple, just be more little green light from the apple that is able to reach the sensor. So how this trait could be useful? Yes! For the detection distance. Let's see the previous graph where we can calculate the distance from the object.

 
Unfortunately the range of the color sensor has a range of no more than a few inches - depending on the brightness of the LED. If you want to be tricked, then it can be used a green laser pointer for maximum range or apply a trick I will show.
The following trick works by the same method with the TV remote to increase the range of the sensor. Normally, if we apply a large amount of power to the LED to increase the brightness, it will cause the LED to burn. But what if it is done in a very short span of time. So we get the right brightness LED 5kali fold to 5 times increase in detection distance.
Back to the basic concept: that power is voltage multiplied by the current. LEDs are usually only work on some miliwatt if it exceeds this, the LED will burn - this is why we always put a resistor in series with the LED (read my previous article about the current-limiting resistor)
As we know that power is a measure of energy divided by time: Energy / sec. So how many times the maximum voltage that can be given to the LED so the LED to shine during 50ms without damage? The answer is 1 / 0, 05 = 20. So we can emit LED light during 20ms with a brightness of up to 20 times without destroying it. Of course, the exact number depends on the thermal cooling rates from the respective LED.
Modulation
There are other methods that can be used to increase the detection range of sensors, called modulation. It's so complicated, so it will not be discussed here, but this requires a sensor that is very fast. The point is that we live transmitter to switch - turns off so fast that the sensor can ignore the background noise. Because the sensor was needed very quickly. Infrared sensors can respond to a few microseconds, but unfortunately photoresistor only able to respond to only a few milliseconds. If desired modulation, would be good if used infrared sensors such as the Sharp IR Rangefinder or can use manufacturer's color sensor Taos.