Project Description

The idea of making this project comes from the actual needs of life, because family members have vitiligo and need long-term phototherapy, that is, 308 ultraviolet irradiation. The cost of a hospital irradiation is about 150 yuan (only a few seconds), and there are also 308 ultraviolet treatment devices sold online, with prices ranging from 1000 to 10000 yuan. After studying, the most important hardware of the sensory therapeutic instrument is the lamp bead and LED driver circuit that can emit 308nm ultraviolet light. As long as the 308nm LED can be bought, and then the driver circuit and related control circuit are added, a "308 ultraviolet therapeutic instrument" is also feasible.

PS: This item is for experiment only and cannot be used as a therapeutic instrument.

Open Source Agreement

GPL-3.0.

Project Related Functions

(1)The main control uses the CW32 low-power series MCU launched by Xinyuan Semiconductor Co., Ltd. to output the PWM signal required for LED boost driving , detect battery voltage, drive 0.91 OLED, etc;

(2) 4 ultraviolet lamp beads are connected in series as a light source, emitting 308nm ultraviolet light;

(3) Constant current LED driver chip model SY7200AABC , input voltage 2.8 to 30V , can drive LED light strings up to 30V , has open circuit protection function, and efficiency is as high as 96% ;

(4) Using a 0.91 OLED screen, it can display battery voltage, LED current, and current PWM duty cycle control parameters;

(5) Powered by two 18650 lithium batteries, rechargeable, 2 LED indicators are used to display the charging status;

(6) Two buttons next to the screen are used to automatically adjust the PWM duty cycle control parameters to control the output power of the UV lamp beads;

(7) Using INA199B1DCKR current sensing amplifier, it can collect LED current in real time;

(8) Use a resistive voltage dividing circuit to realize real-time monitoring of battery voltage;

(9) One-key switch circuit is adopted, making it more convenient to use;

(10) Two LED indicators, one used to indicate the UV light on status, and one used to indicate whether the battery voltage is low;

(11) Using aluminum substrate as LED light panel, heat dissipation is more efficient;

(12) Automatic shutdown after timeout (the program needs to be improved);

(13) Battery power alarm and automatic shutdown when battery power is low (the program needs to be improved);

(14) Use the commercially available flashlight shell, which has low cost and large space for modification.

Device Information

The final product is mainly composed of:   Consists of shell + screen bottom plate + charging board + LED control board + LED light board + battery pack + screws and studs.

(1) Finished shell size: 54*145mm , specific styles are as follows.

(2) Screen bottom board: double-layer board 1.2 board thick, containing 1 piece of 0.91 OLED and 2 5.2*5.2*2.5mm vertical touch switches, connected to the LED control board through cables .

(3) Charging board: double-layer board 1.0 thick, containing TP4056 lithium battery charging circuit, battery /USB power supply switching circuit, 1 vertical Micro-B female base, 1 3 * 6*3.5 side push button The touch switch and 4 LED indicators are connected to the LED control board through cables (the wires in the power supply part should be thickened).

(4) LED control board: a double-layer board with a thickness of 1.6 , which contains the CW32L031C8U6 main control chip, SY7200AABC constant current LED driver circuit, INA199B1DCKR current acquisition circuit, RT9013-33GB voltage stabilizing circuit, voltage sampling circuit and various interfaces.

(5) LED light board: single-layer aluminum substrate 1.6 sheets thick, containing 4 ultraviolet lamp bead strings ( 308nm , voltage 5-7V , current 100MA , power 10-15mW , model 3535 , emission angle 60 degrees), lighting power supply Connect to the LED control board via thick wires . 4 M2 *10 double-pass copper pillars   Fix the LED light board and LED control board together with 8 M2*3 screws .

(6) The battery pack uses two 18650 cells connected in parallel and uses a PH2.0 wire-to-board connector (male)

Project Properties

This project is made public for the first time and is my original project. The project has not won any awards in other competitions.

Project Progress

1. Pre-project preparation

(1) 2023.07.24 Housing selection and procurement, 308nm UV lamp procurement.

(2) 2023.07.26 Measure the internal dimensions of the shell and draw the outline of each functional circuit board in CAD.

2. Project start

(1) 2023.07.27 Main control chip, LED driver chip and current collection chip selection.

(2) 2023.07.28 Schematic diagram and PCB design.

3. Circuit board welding and testing

(1) 2023.08.04 A total of 3 PCBs and 1 aluminum substrate (including: screen base plate, charging board, LED control board, LED light board)

(2) 2023.08.04 Check whether the soldered circuit board has short circuits, weak soldering, etc.

4. Program writing and debugging

(1) Start writing the program on 2023.08.06.

(2) 2023.08.13 Joint debugging of various program functions.

5. Assembly of components

(1) 2023.08.16 Making 2x18650 battery packs.​

(2) 2023.08.16 Install the screen bottom plate, charging board, LED control board, and LED light board to the designated positions in the casing, and secure the battery pack at the same time.

6. Burning program and power-on test

(1) 2023.08.16 Burn the previously written program into the MCU

(2) On August 16, 2023, turn on the power and test whether the ultraviolet lamp can light up and whether the functions are normal.

7. Continue to optimize the program

2023.08.16-2023.09.30.

Design Principles

1. The main control uses CW32L031C8U6 and uses the internal clock.

2. LED cross-current drive circuit, SY7200AABC is used here. The LED lamp is in 4-string mode. The working voltage of a single lamp bead is 6V, and the total voltage after boosting is 24V. R7 uses a 1.3 ohm 2512 resistor to limit the maximum output current of the circuit to no more than 150mA (the working current of the lamp bead is 100mA-150mA).

3. Screen bottom panel, including a 0.91 OLED and 2 buttons.

4.Charging board. Adopts TP4056 chip, and adds a battery/USB power supply switching circuit.

5. One-button switch circuit.

One-button power-on principle: After the power button is pressed, the Q1 tube is turned on and the microcontroller starts to work. After the program is run, PA2 detects a low level, and then pulls PA5 high and Q2 is turned on. After the power button is released, because Q2 is still On, Q1 is still in continuous conduction state, and one-button power-on is completed.

Principle of one-key shutdown: After the power button is pressed, PA2 detects a low level for more than 6 seconds. The main control will pull PA5 low and Q2 is turned off. After releasing the power button, the gate of Q1 is pulled high by R3. Q1 is also shut down, and one-click shutdown is completed.

Software Description

The program is developed using KEIL5 software, and the library files inside are transplanted from the open source programs of some big names on the Internet. Due to my limited level, I have only implemented basic functions for the time being. There are still some unknown BUGs and functions that need to be improved. I will slowly improve them in the future.

1. Main function initialization part

2. Main function part

3. Voltage and current calculation part functions

Physical Display

1.LED control board

2. Screen base

3.Charging board

4.LED light panel

5. Assembly drawing

 (1) Solder the connections between the boards.

(2) Install each function board in the corresponding position.

(3) Lead to the burning port and burn the program.

(4) Remove the burning wire and fix the light board to the LED control board through four M2 studs.

(5) Remove the original battery and replace it with the 18650 battery pack.

(6) After the test is OK, close the shell and install the fixing screws.

(7) Install the lamp head protective cover.

(8)successfully accomplished.

(9) Test

Video address:  https://www.bilibili.com/video/BV1zm4y1u7a6/?share_source=copy_web&vd_source=9ba8a1a42740c64300efbea6bc94c293

Announcements

(1) Do not look directly at the ultraviolet light source, otherwise your eyes will be seriously injured.

(2) A single use should not exceed 10 seconds, otherwise it will cause damage to the skin.

(3) This UV lamp cannot be used by children.

(4) This item is for experiment only and cannot be used as a therapeutic instrument.

Other

The final effect of this project is still under testing.

Because it is difficult to control the intensity and time of irradiation, the irradiation power was a bit high during the first test, causing some burns on the skin. It is recommended to use low power and short-term irradiation.

The program is in the attachment below, please use KELI5 to open it.