Simple light meter based on Arduinocopy

**1 Overview**

A simple light meter based on Arduino nano.
The original project is sourced from Bilibili UP: Running Bear. Direct video link: [https://www.bilibili.com/video/BV1B54y1B7q](https://www.bilibili.com/video/BV1B54y1B7qV)

I hope all friends will watch the video Here, you can run away the boss with three clicks and support him.

The open source agreement of the Paojiao Xiong project is based on GPL 3.0 (which has been confirmed by me). The agreement simply states that it is open source, free of charge, and can be modified at will, but it requires that it be open sourced after modification.

I add: This PCB is strictly prohibited for commercial use.

UP's original project did not have a PCB, and UP's consent was obtained to modify and draw the PCB open source on the original schematic diagram.
The total cost of the light meter of the original project is 30 yuan; this PCB adds lithium battery charging and discharging, Micro USB power supply, external 3V/5V/9V (vin) power supply, buttons with Chinese culture, and optimized circuit layout. The estimated cost is about 40 yuan.
This light meter is not accurate, and ordinary negative film can handle it. If you have high requirements for light measurement, you can choose a commercial light meter.

1.1 The actual situation of board making
![IMG_20200629_143409.jpg] ![IMG_20200629_143415.jpg] 1.2 Display after welding
![wx_camera_1593418550822.jpg]
**2 Required originals**
Arduino nano control board;

BH1750 light intensity module;

0. 96-inch 7-pin SPI Interface oled screen (SSD1306);

micro switch;

100~200mAh lithium battery;

HW-357 3.7V liter 5V~9V lithium battery charge and discharge module;

toggle switch;

Micro USB female port;

2.1 Display of required originals
! [IMG_20200629_144434. jpg]
3 Physical assembly and demonstration

3.1 Precautions for installing lithium battery module

![IMG_20200629_153813.jpg] ![IMG_20200629_153829.jpg]
Solder the pin header on the lithium battery module from the back, and match the pin header with the empty space on the module silk screen on the PCB one by one. Insert the pin header into the PCB board and solder it, use wire cutters to cut off the protruding pin header part, and the module is welded.

3.2 Remaining welding precautions

Arduino nano and OLED screens are installed on the front of the PCB according to the silk screen prompts. You can choose whether to install a female header (it will be more beautiful if not installed, but the disadvantage is that the module cannot be removed). The BH1750 light metering module is installed on the back of the module according to the silk screen printing. The lithium battery must be connected to the pad of the "lithium battery interface". If it is connected to the module, the switch will become invalid. The lithium battery can be pasted on the back of the PCB, and a sponge can be sandwiched between the lithium battery and the PCB to prevent short circuit and buffer.

4 Operation

4.1 Light meter operation method

After powering on, press the metering button to measure the light in a single time; press the increase/decrease button to increase/decrease the current option value; press the priority button to switch shutter priority/aperture priority; After pressing the menu button, use the increase/decrease keys to adjust the ISO and exposure gears; the measurement mode can be switched between incident and reflective measurement methods.

4.2 Actual accuracy of light meter use

! [IMG_20200629_171524.jpg] ![IMG_20200629_171415.jpg]
Operation video to be uploaded on
2020.06.30