Four photoelectric detection parallel detection characteristics
- Common base amplifier circuit isolates the influence between photoelectric tubes
- Reflective infrared detection circuit based on LM567, used in energy-saving beacon detection circuit
01Chain detection module
I. Introduction
Yesterday, we tested the solution of using a microcontroller to detect the passing of a car model. Especially for a single detection point, using a 1.25kHz pulse can achieve good detection results. Next, connect the four detection points in parallel to verify the detection effect.
2. Circuit design
According to yesterday's experimental results, each detection module circuit is the same. It has two three-core interfaces, one in and one out. After the input forward pulse is rectified by the Schottky diode D2, the energy is stored on the C10 capacitor. This voltage is provided to the phototransistor as a working power source. In fact, D2, C10, and C11 can be used without welding during work. It can also have the same effect. It's just that the noise will be louder. Design single-sided circuit boards for easy testing using the one-minute pattern making method.
Use rapid pattern making to make six modules, and then conduct welding tests on them. Preliminarily verify the feasibility of this chain detection module. As for how many blocks is the upper limit, it will be measured through the official version in the future.
3. Welding debugging
Using the devices you have on hand, solder the test sensor board. There are four small boards in total. Use cables to connect them in series below.
The four welded sensor modules are connected in series, the last connector is connected to the breadboard, and connected to yesterday's microcontroller module for testing.
4. Test results
At the receiving end, adding a 47nF capacitor can reduce the noise in the received data. It can be seen that the feedback current will fluctuate up and down as the palm passes on the photoelectric sensor. Test each sensor to complete the detection function for passing palms and car models.
One problem can be seen through observation, that is, the amplitude of the up and down fluctuations of the received signal is reduced. The signal presents a triangular waveform, which shows that four sensors are connected in parallel and the equivalent bandwidth becomes smaller. By reducing the pulse frequency eight times, you can see that the up and down fluctuations of the waveform become larger. It is proved here that after the photoelectric tubes are connected in parallel, the overall reaction speed is reduced. At low frequencies, you can see that the amplitude of the waveform's up and down fluctuations has indeed increased.
▲ 图1.4.1 测量上下波动幅度
※ Summary ※
This article tests four solutions based on parallel connection of photoelectric tubes to detect the passing of car models. The system does work, but after parallel connection, the response speed of the overall sensor is reduced. ·This part needs to be improved, otherwise it cannot adapt to the narrow pulse corresponding to the high-speed car model passing by.
Supplementary experiments
Next, six photoelectric collectors are connected in parallel, and the response speed is also very slow.
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