TCS230 color sensor and color recognition circuit
As the modern industrial production to high-speed, automated direction of the development, production process of a long period of time by the human eye color play a leading role will be to identify more and more the color of the corresponding sensors are replaced. For example: the use of color to distinguish between library classification literature, can greatly improve the management and statistical bent, etc.; in the packaging industry, product packaging or the use of different colored decoration to express their different nature or use. At present, the color sensor is usually an independent photodiode covered amended red, green, blue filter, and then the corresponding output signal processing, color signal can be identified; some of the two together output analog signals, however, need a A / D sampling circuit, the signal for further processing, in order to identify and increase the complexity of the circuit, and the identification of a large error, the impact of the identification results. TAOS (Texas Advanced Optoelectronic Solutions)'s new color sensor TCS230, the color can be achieved not only the identification and detection, and compared to the previous color sensors, but also has many excellent new features.
1 TCS230 chip block diagram of the structure and characteristics of
TAOS company is TCS230 programmable color light introduced to the frequency converter. It can be configured to the silicon photodiode and current-frequency converter integrated in a single CMOS circuits at the same time in a single chip integrated red-green-blue (RGB) filter of three, is the industry's first digital-compatible interface the RGB color sensor. TCS230 output signal is digital, you can drive standard TTL or CMOS logic input, it can be directly related to the microprocessor or other logic circuits connected. As the output is digital and can be realized for each color channel of more than 10-bit conversion accuracy, and therefore no longer necessary A / D conversion circuit, the circuit easier. TCS230 Figure 1 is a block diagram of the pin and function.
Figure 1, TCS230 in an 8-pin SOIC surface mount package, in a single chip photodiode 64. These diodes are divided into four types. Which the photodiode 16 with a red filter; 16 photodiode with the green filter; photodiode 16 with a blue filter; the remaining 16 without any filter, through all the optical information. These photodiode chip is in the cross-array, to minimize the inhomogeneity of the incident radiation, thereby increasing the accuracy of color recognition; On the other hand, the same color of the photodiode 16 is connected in parallel, uniform distribution in the diode array, you can eliminate errors in the position of color. Work, through the two-pin programmable to dynamically select the required filter. The sensor of a typical output frequency range from 2 Hz ~ 500 kHz, the user can also choose the two pin-programmable 100%, 20% or 2% of the output scale factor, or power shutdown mode. Output scale factor so that the output of the sensor to adapt to a different measurement range and improve its adaptability. For example, when using low-speed frequency counter, you can choose a small calibration value, so that the output frequency and TCS230 counter match.
We can see from Figure 1: When the incident light, when projected onto the TCS230 through control pin photodiode S2, S3 of the different combinations, you can choose a different filter; after current to frequency converter after the output square wave of different frequencies (or space ratio is 50%), different colors and light intensity corresponding to different frequencies of square wave; also can be controlled through the calibration output pin S0, S1, choose a different output scale factor, output frequency range to be adjusted to adapt to different demand.
Figure 1 TCS230 diagram of the pin and function
TCS230 chip following a brief introduction of the various pin functions and some of its portfolio of options.
S0, S1 is used to select the output scale factor or power shut-off mode; S2, S3 is used to select the type of filter; OE is the frequency output enable pin to control the output state, when there are several common micro-chip-pin processor input pin, it can be used as chip select signal; OUT is the frequency output pin, GND is the grounding pin chip, VCC operating voltage for the chips. Table 1 shows the S0, S1 and S2, S3 can be used in combination.
Table 1 S0, S1 and S2, S3 combination of options
2 TCS230 color recognition principle
Introduced by the above we can see, this programmable color light to frequency converter suitable colorimeter measurement applications, such as color printing, medical diagnostics, computer color monitor calibration, as well as paints, textiles, cosmetics and the process of printing materials control and color match. Below the liquid TCS230 Color Recognition as an example, the specific use of it. First of all, understand the knowledge of light and color.
(1) the induction principle of the three primary colors
Usually see the color of objects, in fact, is the object's surface to absorb the radiation to which the above white (daylight) in the part of non-ferrous components, while reflecting light of another part of the reaction in the eyes. White is the frequency of visible light from a variety of mixed composition, that is contained in a variety of white color light (eg, red R, Huang Y, Green G, Green V, blue B, purple P). According to Helmholtz the German physicist (Helinholtz) theory, we can see the three primary colors, a variety of colors by the different proportions of the three primary colors (red, green, blue) of a mixture.
(2) TCS230 color recognition principle
Induction principle, we can see from the three primary colors, a variety of colors, if aware of the value of the three primary colors, will be able to know the color of the test object. TCS230 For example, when a color filter when selected, it only allows the adoption of a particular color, to prevent the passage of other colors. For example: when you select a red filter, the incident light can be only red, blue and green have been prevented, it can be light red light; Similarly, choose a filter, you can get the blue light light green light. Through these three values can be projected onto the analysis of the optical sensor TCS230 color.
(3) white balance and color recognition principle
White balance system is to tell what is white. In theory, the same amount of white is red, green and blue mixture; But in fact, the three primary colors and white is not entirely the same, and optical sensors for the TCS230, it's the three the sensitivity of the basic color is not the same, leading to the RGB output TCS230 is not the same, so the test must be carried out before the white balance adjustment, making TCS230 for the detection of "white" of the three primary colors are equal. White balance adjustment is carried out for the follow-up in preparation for the color identification. In this device, the white balance adjustment of the specific steps and methods are as follows: the empty test tube placed in the top of the sensor, test-tube placed above a white light source, so that incident light can pass through in vitro exposure to the TCS230; introduced under the previous method, followed by gating red, green and blue filters, respectively, the measured red, green and blue values can be calculated and then need to adjust the parameters of the three.
When TCS230 color identification on the use of these three parameters on the measured colors of R, G and B to adjust. There are two ways to calculate the adjustment of parameters: ① strobe followed by three color filters, and then followed by TCS230 output pulse counting. When the counting to stop counting at 255, respectively, for each channel used in the calculation of the time. Corresponds to the time when the actual testing of each filter used TCS230 time base during this period of time measured is the pulse number corresponding to the R, G and B value. ② Set the timer for a fixed time (for example, 10 ms), and then gating the three color filters, calculating the period of the output pulses TCS230, a scaling factor calculated by the scale factor can be a number of these pulses to 255. In the actual test, using the same time to count the pulses measured multiplied by the scale factor to achieve, and then can be corresponding to R, G and B value.
application of 3 TCS230 - Color identification circuit
Based on the above analysis, the use of 89C51 and the design of a medical liquid TCS230 color identification devices. The device has a simple structure, high precision and efficiency to identify the characteristics of, and be able to host computer communications, in order to identify the results of real-time transmission to the host computer. TCS230 is that as a result of the use of one of the following TCS230 only recognition given circuit, as shown in Figure 2. Figure 2 with the P1 population 89C51 several software processes Figure 3-pin to control the various control pin TCS230, TCS230 output and the pin connected to the 89C51 timer / counter 1 input (P35). Set 89C51 timer / counter for the corresponding work, 89C51 timer is initialized to a value, and then select the TCS230 output scale factor, and can output pins. Actual use, by reading 89C51 counter value can be calculated on the TCS230 output frequency of three kinds, which determine the R, G, B value and color. Software processes as shown in Figure 3.
Figure 2 TCS230 color recognition interface circuit
Process in the process: The system initialization is responsible for setting the 89C51 timer / counter work, select TCS230 output scale factor, so that the output pin and set up communication parameters. Initialization is complete, testing the need for white balance adjustment. If so, adjust the white balance subroutine; Otherwise, go to the next step, testing the need for color recognition. If the color does not need to identify, to return; such as the need for color recognition, color recognition subroutine calls, until the end of color recognition.
Figure 3 software process
4 applications need to pay attention to
① color to prevent the outside world to identify the interference of light, or will affect the results of color recognition. Best sensors, light sources, such as placed in a sealed, non-reflective of the box for testing.
② to the light source there are no special requirements, but the light source to be concentrated as much as possible, otherwise it will create mutual interference between sensors.
③ When the 1st to use when TCS230, TCS230 Identity Module, or restart, the replacement of light source, etc., they need to adjust the white balance.
TCS230 article from the characteristics of the structure, introduced the theory of light and color to identify the knowledge, as well as white balance adjustment of the principles and methods. Combination of a specific application, the corresponding circuit of the hardware design and software flow chart. The sensor and the Sultan of the method described in the color of other identification, but also a great help.
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