VFD fluorescent screen 12-bit 5x7 module

# VFD fluorescent screen driver module 12-bit 5x7 dot matrix
> This VFD display driver module was produced with reference to the open source circuits of other experts, combined with understanding and learning

! [21f8ec565324550d5537bc9d72d8f94.jpg] ![8f9ef61a2d2df066561956ba6dc0c65.jpg] ## VFD screen
description This screen is a 12-bit 5x7 dot matrix screen that I bought for 6 yuan from picking up trash on Taobao. The power supply for the filament is AC. The following are some of the power requirements of this screen.


| Project | Code | Min | Standard | Max | Unit |
| --- | --- | --- | --- | --- | --- |
| Filament voltage | ef | 3.24 | 3.6 | 3.96 | Vac |
| Peak anode voltage | eb | 27 | 30 | 33 | Vp-p |
| Peak grid voltage | ec | 27 | 30 | 33 | Vp-p |
| Cutoff bias voltage | ek | 5.7 | - | 8.3 | vdc |
Filament current: ef = 3.6Vac [min: 90mA ac ype: 100mAacmax:110mAac] Recommended filament voltage 3.6Vac current 100mAac

![image.png] **For this VFD screen, the start pin of the 5x7 dot matrix is ​​P2, The P1 pin is the display pin of the icon above**

## Drive circuit
### Negative high voltage circuit
! [image.png] MC34063 chip, this chip can increase and decrease voltage, and can also increase negative voltage.
Chip documentation: [PDF document](http://pdf-html.ic37.com/pdf_file_A/20200531/pdf_pdf/pdf1/STMICROELECTRONICS/MC34063_datasheet_444417/724452/MC34063_datasheet.pdf)
Calculation formula:
Vout = Desired output voltage; Vout| = 1.25(1+R2/R1);
1.25 * (1+ 240/10) = 31.25; R3 = 240K R2 = 10K
In the above figure, L1 = 100uH. It is best to choose a large inductor with a large current and a Schottky diode. diode.

### AC filament drive circuit
![image.png] AC drive will make the VFD brightness more uniform.
The driver chip selected the motor-driven chip **MX612E**. It needs to match the input of PWM signal.
The best measured PWM signal is 50% duty cycle and 10Khz frequency.

**Filament debugging method:**
1. Adjust the frequency to a higher value. The redness of the filament is visible to the naked eye
. 2. Slowly reduce the frequency
. 3. Until it is visible to the naked eye, it is just at the critical point and does not turn red. No light can be seen.
4. If the filament turns red, it will affect the service life and cause damage.

## Driver chip PT6302LQ-xxx
>PT6302 is a dot matrix VFD driver/controller IC
that uses specially designed CMOS technology
to display characters, numbers and symbols. Model PT6302
provides 35 dots, 2 additional segment drivers
and 16 gate drivers. 248 types of character data
(CGROM), 8 types of character data (CGRAM), 16
display digits x 2-bit symbol data, 16 display digits x 8 bit
registers for character data display and 2 general-purpose registers
are provided for Output bit for static operation. Pins are optimized for easy PCB layout and cost-saving advantages in distribution
and application circuitry . **This chip comes with a font library, which is very convenient for development. And there are many pins for segments and bits. The one on Taobao that offers free shipping for 3.5 pieces is ** ![image.png] --- # Arduino driver code ![image.png] This project is a semi-finished project, you just need to find Just copy the next two files in this file to your project. For usage methods, please refer to the usage examples in the main.cpp file under this project. Github link: https://github.com/ccy-studio/ESP32-VFD-V1