#The 4th LiChuang Competition# Capacitive touch proximity two-in-one induction faucet

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* Briefly introduce the work: Capacitive touch proximity two-in-one induction faucet
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* 1. Work details;
This work is different from the traditional infrared induction faucet. Infrared induction relies on reflection. Various reflective objects will block the water flow within the effective distance, and some cannot be used under sunlight or strong light. Otherwise, it will cause abnormal execution or complete failure. This proximity induction faucet changes based on the change of the human body's capacitance to the ground and the capacitance of the induction plate, and there is no influence from the ambient light of the place. The sensing position is within 50MM in all directions except the top direction of the induction main control board. If the sensing value reaches the opening threshold, water will flow out, and the water flow time is 1S to 3S. The user can choose to set the water flow time. Touching means immediate water flow, and proximity means a delay of 0.5S before water flow. In both methods, the water flow stops immediately when the hand is released or the hand is placed within the sensing area for more than the water flow time, and the water flow stops immediately, and it will be kept until the hand leaves the sensing area before the next water flow operation can be entered.
This work can completely replace infrared induction faucets. It is mainly used in public places and family toilets to save water. It can also effectively prevent secondary infection of hands.
Water flow time setting process: When the power is turned on for the first time or again, the water flow time setting mode will be entered. It will not be until the user presses the touch switch of the switch board for 2S that the water flow time setting mode can be exited and the working mode can be entered. When the water flow time needs to be set, the time will be increased by 1 if the touch switch is pressed briefly. Three water flow time numbers from 1 to 3S are set. If the short press is pressed, the 1S to 3S cycle will continue. At the same time, the switch board indicator light will flash according to the water flow time number, flashing once for 1S, flashing twice for 2S, flashing three times for 3S, and 3.5S as a cycle. After pressing for 2S, the switch board indicator light will stay on for 1S and then go out, and the working mode will be completely entered.
* 2. Describe the challenges faced by the work and the problems solved;
The challenges faced by the work are that the faucet bracket is made of metal, which is easy to introduce electromagnetic interference and affect the capacitive touch detection, such as causing abnormal water flow in the work, for example: insensitive sensing or program runaway causing continuous intermittent water flow.
The standby power consumption is too large. The average is ≤0.12W. It is very unfavorable for battery power supply. The standby time is about one day and the battery needs to be replaced.
Because the touch main control board and the switch board are separated, they are connected with 4P cables. If the circuit used in the previous work is improved, the wiring will be poor due to wiring problems, which will cause the switch board to be powered for a long time due to the conduction of the PMOS tube, causing the switch tube TDA2822 to be turned on and heated, burning the circuit board components.
In view of the above three points, the first point should be started from the following two aspects: one is to optimize the configuration parameters of the third-party touch library of the program. The second is to increase the number of checks for cumulative judgment. The third is that the hardware should connect the faucet bracket to the GND of the touch PCB. Reduce some interference signals. The second point is that the MCU software and hardware resources required by the third-party touch library cannot be actively controlled. It can only be passively controlled. It is necessary to make a DC dual power supply mode so that the battery does not need to be replaced frequently, and the battery can be used as a backup power supply. The third point is to use NMOS and NPN transistors to control the switch board. *
* 3. Describe the key points involved in the hardware and software parts of the work;
hardware key points. The main control board and the switch board are connected by 4P cable. The difference between the switch board before and after improvement is that when the main control board and the switch connection line have poor contact, the latter will not supply power to TDA2822. The former will continue to supply power and cause TDA2822 to burn out. And accelerate battery discharge and reduce battery life.
During use, when the battery voltage drops below the LVR of the MCU, the MCU resets due to undervoltage and re-enters the water output time setting mode. At this time, the main control board and the switch board indicate a flashing frequency of 0.5S on and 3S off, which is a reminder to replace the battery.
Software key points. Use the Saiyuan special high-sensitivity touch library and use the Saiyuan touch debugging software to adjust the most suitable sensing distance. * 4. List of materials for the work;
One 5V pulse solenoid valve.
One 9V stacked battery.
One faucet bracket.
Two water hoses.
* 5. Upload pictures of your work; (The PCB must have the competition logo and take a photo and upload it. If not, it will be considered as giving up the competition)
* 6. Demonstrate your work and upload it as a video; (The video content must include: work introduction; function demonstration; performance test; close-up of the competition logo on the PCB. If not, it will be considered as giving up the competition)
Please see the attachment.
   7. Open source documents.
Please see the attachment.