Overview:
The TCS3200 and TCS3210 programmable color
light-to-frequency converters that combine configurable silicon photodiodes and
a current-to-frequency converter on a single monolithic CMOS integrated
circuit. The output is a square wave (50% duty cycle) with frequency directly
proportional to light intensity (irradiance). The full-scale output frequency
can be scaled by one of three preset values via two control input pins. Digital
inputs and digital output allow direct interface to a microcontroller or other
logic circuitry. Output enable (OE) places the output in the high-impedance
state for multiple-unit sharing of a microcontroller input line. In the
TCS3200, the light-to-frequency converter reads an 8 x 8 array of photodiodes.
Sixteen photodiodes have blue filters, 16 photodiodes have green filters, 16
photodiodes have red filters, and 16 photodiodes are clear with no filters. In the
TCS3210, the light-to-frequency converter reads a 4 x 6 array of photodiodes.
Six photodiodes have blue filters, 6 photodiodes have green filters, 6
photodiodes have red filters, and 6 photodiodes are clear with no filters. The
four types (colors) of photodiodes are interdigitated to minimize the effect of
non-uniformity of incident irradiance. All photodiodes of the same color are
connected in parallel. Pins S2 and S3 are used to select which group of
photodiodes (red, green, blue, clear) are active. Photodiodes are 110 μm x 110
μm in size and are on 134-μm centers.
Colour Sensor:
Functional Block Diagram:
APPLICATION
INFORMATION:
Power
supply considerations:
Power-supply lines must be
decoupled by a 0.01-μF to 0.1-μF capacitor with short leads mounted close to
the device package.
Input
interface:
A low-impedance electrical
connection between the device OE pin and the device GND pin is required for improved
noise immunity. All input pins must be either driven by a logic signal or
connected to VDD or GND —they should not be left unconnected (floating).
Output
interface:
The output of the device is
designed to drive a standard TTL or CMOS logic input over short distances. If
lines greater than 12 inches are used on the output, a buffer or line driver is
recommended. A high state on Output Enable (OE) places the output in a
high-impedance state for multiple-unit sharing of a microcontroller input line.
Power
down
Powering down the sensor using
S0/S1 (L/L) will cause the output to be held in a high-impedance state. This is
similar to the behavior of the output enable pin, however powering down the
sensor saves significantly more power than disabling the sensor with the output
enable pin. Photodiode type (color) selection The type of photodiode (blue, green,
red, or clear) used by the device is controlled by two logic inputs, S2 and S3
Output
frequency scaling:
Output-frequency scaling is
controlled by two logic inputs, S0 and S1. The internal light-to-frequency
converter generates a fixed-pulse width pulse train. Scaling is accomplished by
internally connecting the pulse-train output of the converter to a series of
frequency dividers. Divided outputs are 50%-duty cycle square waves with
relative frequency values of 100%, 20%, and 2%. Because division of the output
frequency is accomplished by counting pulses of the principal internal
frequency, the final-output period represents an average of the multiple
periods of the principle frequency. The output-scaling counter registers are
cleared upon the next pulse of the principal frequency after any transition of
the S0, S1, S2, S3, and OE lines. The output goes high upon the next subsequent
pulse of the principal frequency, beginning a new valid period. This minimizes
the time delay between a change on the input lines and the resulting new output
period. The response time to an input programming change or to an irradiance step
change is one period of new frequency plus 1 μs. The scaled output changes both
the full-scale frequency and the dark frequency by the selected scale factor. The
frequency-scaling function allows the output range to be optimized for a
variety of measurement techniques. The scaled-down outputs may be used where
only a slower frequency counter is available, such as low-cost microcontroller,
or where period measurement techniques are used.
Measuring
the frequency:
The choice of interface and
measurement technique depends on the desired resolution and data acquisition rate.
For maximum data-acquisition rate, period-measurement techniques are used. Output
data can be collected at a rate of twice the output frequency or one data point
every microsecond for full-scale output. Period measurement requires the use of
a fast reference clock with available resolution directly related to reference
clock rate. Output scaling can be used to increase the resolution for a given
clock rate or to maximize resolution as the light input changes. Period
measurement is used to measure rapidly varying light levels or to make a very
fast measurement of a constant light source. Maximum resolution and accuracy
may be obtained using frequency-measurement, pulse-accumulation, or integration
techniques. Frequency measurements provide the added benefit of averaging out
random- or high-frequency variations (jitter) resulting from noise in the light
signal. Resolution is limited mainly by available counter registers and
allowable measurement time. Frequency measurement is well suited for slowly
varying or constant light levels and for reading average light levels over
short periods of time. Integration (the accumulation of pulses over a very long
period of time) can be used to measure exposure, the amount of light present in
an area over a given time period.
ARM SCHEMATIC:
ARM CODE:
ATMEL Schematic:
ATMEL CODE:
For ATMEL code
Click Here
PIC Schematic:
PIC CODE:
