走马观花

Analog and five-digit source meter/ammeter (2) display part

 
Overview

Introduction: This is the second part of the first part.
1. Product introduction:

This is the display part of a multi-purpose indicator meter. It can be used in combination with the first part to form a source meter/ammeter, or it can be used alone as a meter head, which can be driven according to the interface protocol.


2. Application scenarios:

meter heads of ammeters, voltmeters, and UV meters


3. Product overview:

The meter heads use 40 LEDs as analog strips, driven by the LM3914 analog chip.

The current setting is dot display, with up to two LEDs lighting up at the same time.

The screen is a 0.96-inch white OLED screen, which can also be replaced with an I2C protocol screen of other sizes.

Use a 12pin flexible cable to connect. Please refer to the schematic diagram for interface definition.


4. Product parameters:

Analog strip: 40 LEDs, indicating the voltage value of 0-2.048V (default).

Screen: 0.96-inch OLED, display content can be freely defined.

There is also a WS2812B colored light for additional information display.


The power supply requires 4 channels, which are:

Analog power supply: 5V (adjustable)

Digital part: 5V

Screen driver: 3V 3

Voltage reference: 2.048V (adjustable)


5. Instructions for use:

Analog strip

analog strip power supply, this project is set to 5V , can be adjusted according to your needs and the LM3914 chip.

The voltage range is: (voltage reference +1.6V) to 15V. Please refer to the LM3914 Datasheet for details.

The voltage reference affects the display range of the LED light. For example, the default is 2.048V. When the signal input voltage is 2.048V, the last 40th LED will be lit. The interval voltage of each LED is: voltage reference/40. It is recommended that this value be greater than or equal to 50mV to avoid overlapping display and making it difficult to distinguish.

If the voltage reference does not exceed 3V3, the power supply of the analog strip can also share the 5V power supply with the digital part.


The screen

uses the I2C protocol. This part comes directly from the OLED conventional driver board. If your screen has a separate driver circuit or voltage and current configuration, please modify the parameters of this part.


Indicator light

The indicator light is composed of 6 WS2812B full-color lights, and the display content can be freely defined. The layout is relatively loose and can be modified to the position you need.

When used with the first part of the project, the current range is displayed.


6. Remarks:

This meter can be used alone, or it can be used with the main control board of "Analog and Five-Digit Source Meter (1) Control Part" to form a complete ammeter. Please search for this project on the homepage.

This meter does not have an MCU and does not require program burning.


The main cost of production is approximately:

LM3914 (about 5 yuan/unit) + 40*0402LED ≈ 30 yuan

OLED screen ≈ 7 yuan

and other components <10 yuan.

For the purchase of screens and cables, please refer to the note: Purchase link.zip.

Since the PCB does not have silk screen printing, please download the attachment: Mounting point bitmap.zip for mounting, or use Lichuang EDA Professional Edition to import local files and use the welding assistant. Carry out placement.

For more information, please refer to: Analog and Five-digit Source Meter (1) Control Part


7. Test video:

The video shows the accuracy test (after calibration) and the test of switching from the microampere-5A gear.


参考设计图片
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Update:2025-07-01 10:56:50

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