21-09-2012, 02:58 PM
Colour Sensor
[attachment=34269]
Colour sensor is an interesting
project for hobbyists. The circuit
can sense eight colours, i.e. blue,
green and red (primary colours); magenta,
yellow and cyan (secondary colours); and
black and white. The circuit is based on
the fundamentals of optics and digital
electronics.
The object whose colour is required
to be detected should be placed in front
of the system. The light rays reflected
from the object will fall on the three
convex lenses which are fixed in front
of the three LDRs. The convex lenses
are used to converge light rays. This
helps to increase the sensitivity of
LDRs.
Blue, green and red glass plates
(filters) are fixed in front of LDR1, LDR2
and LDR3 respectively. When reflected
light rays from the object fall on the
gadget, the coloured filter glass plates
determine which of the LDRs would get
triggered. The circuit makes use of only
‘AND’ gates and ‘NOT’ gates.
When a primary coloured light ray
falls on the system, the glass plate corresponding
to that primary colour will
allow that specific light to pass through.
But the other two glass plates will not
allow any light to pass through. Thus
only one LDR will get triggered and the
gate output corresponding to that LDR
will become logic 1 to indicate which
colour it is.
Similarly, when a secondary coloured
light ray falls on the system, the two
primary glass plates corresponding to the
mixed colour will allow that light to pass
through while the remaining one will not
allow any light ray to pass through it. As
a result two of the LDRs get triggered and
the gate output corresponding to these
will become logic 1 and indicate which
colour it is.
1. Potmeters VR1, VR2 and VR3 may
be used to adjust the sensitivity of the
LDRs.
2. Common ends of the LDRs should
be connected to positive supply.
3. Use good quality light filters.
The LDR is mounded in a tube,
behind a lens, and aimed at the object.
The coloured glass filter should be fixed
in front of the LDR as shown in the
figure. Make three of that kind and
fix them in a suitable case. Adjustments
are critical and the gadget performance
would depend upon its proper fabrication
and use of correct filters as well as
light conditions.
[attachment=34269]
Colour sensor is an interesting
project for hobbyists. The circuit
can sense eight colours, i.e. blue,
green and red (primary colours); magenta,
yellow and cyan (secondary colours); and
black and white. The circuit is based on
the fundamentals of optics and digital
electronics.
The object whose colour is required
to be detected should be placed in front
of the system. The light rays reflected
from the object will fall on the three
convex lenses which are fixed in front
of the three LDRs. The convex lenses
are used to converge light rays. This
helps to increase the sensitivity of
LDRs.
Blue, green and red glass plates
(filters) are fixed in front of LDR1, LDR2
and LDR3 respectively. When reflected
light rays from the object fall on the
gadget, the coloured filter glass plates
determine which of the LDRs would get
triggered. The circuit makes use of only
‘AND’ gates and ‘NOT’ gates.
When a primary coloured light ray
falls on the system, the glass plate corresponding
to that primary colour will
allow that specific light to pass through.
But the other two glass plates will not
allow any light to pass through. Thus
only one LDR will get triggered and the
gate output corresponding to that LDR
will become logic 1 to indicate which
colour it is.
Similarly, when a secondary coloured
light ray falls on the system, the two
primary glass plates corresponding to the
mixed colour will allow that light to pass
through while the remaining one will not
allow any light ray to pass through it. As
a result two of the LDRs get triggered and
the gate output corresponding to these
will become logic 1 and indicate which
colour it is.
1. Potmeters VR1, VR2 and VR3 may
be used to adjust the sensitivity of the
LDRs.
2. Common ends of the LDRs should
be connected to positive supply.
3. Use good quality light filters.
The LDR is mounded in a tube,
behind a lens, and aimed at the object.
The coloured glass filter should be fixed
in front of the LDR as shown in the
figure. Make three of that kind and
fix them in a suitable case. Adjustments
are critical and the gadget performance
would depend upon its proper fabrication
and use of correct filters as well as
light conditions.