Color Sensor

This is the color sensor circuit diagram. Color sensor is definitely an exciting project for hobbyists. The circuit can sense eight colors, i.e. blue, green and red (primary colors); magenta, yellow and cyan (secondary colors); and black and white. The circuit is based on the fundamentals of optics and digital electronics.

The object whose color is needed to be detected ought to be put in front of the circuit/sensor. The light rays reflected from the object will fall on the three convex lenses that are mounted in front of the three LDRs. The convex lenses are utilized to converge light rays. This helps to improve the sensitivity of LDRs.

Blue, green and red glass plates (filters) are fixed in front of LDR1, LDR2 and LDR3 correspondingly. When reflected light rays from the object fall on the device, the colored filter glass plates decide which of the LDRs would get triggered. The circuit makes use of only “AND” gates and “NOT” gates.

When a primary colored light ray falls on the system, the glass plate corresponding to that primary color will permit that certain light to pass through. However the other two glass plates is not going to permit any light to pass through. Thus only one particular LDR will get triggered and the gate output corresponding to that LDR will become logic 1 to indicate which color it can be.

Similarly, when a secondary colored light ray falls on the system, the two primary glass plates corresponding to the mixed color will permit that light to pass through whilst the remaining one is not going to permit any light ray to pass through it. As a result two of the LDRs get triggered and the gate output corresponding to these will come to be logic 1 and indicate which color it really is.

When all of the LDRs get triggered or stay untriggered, you will observe white and black light indications respectively. Following factors might be carefully noted:

1. Potensiometers VR1, VR2 and VR3 may possibly be applied to alter the sensitivity of the LDRs.
2. Use good quality light filters.
3. Common ends of the LDRs need to be joined to positive supply.

The LDR is mounted within a tube, behind a lens, and aimed at the object. The colored glass filter need to be fixed in front of the LDR as shown in the figure. Make three of that kind and fix them inside a appropriate case. Adjustments are essential and also the gadget functionality would depend upon its correct fabrication and utilization of proper filters as well as light conditions.

Download color sensor circuit document in PDF file: