Multiple LCD modules on one Nano - faint display

[lesthegrngo]

Guys, as you can see my CMSC panel has three 8 x 1 LCD modules in it, and I have been able to make them run off one Nano board. Basically each LCD module is connected to a PCF8574 adapter which allows different I2C addresses

 

However when I was putting it back together after some testing work, I noticed something I hadn't seen before. I connected the LCD modules one by one to make sure they all were connected to the right panel, and as I connected each one, the displays became fainter. Obviously I checked the settings with the potentiomenters, but even at max settings, by the time all three were connected the display was very faint indeed.

 

All the schematics I have seen show the GND and VCC of the LCD displays connected to the Nano GND and 5v pins. Should there be a separate 5v supply to the PCF8574 boards?

 

Cheers

 

Les

Edited April 10, 2020 by lesthegrngo

[lesthegrngo]

Guys, I fixed this by connecting a 5v supply to the VC and GND pins. Lovely clear displays now, and checking the Nano '5v' output showed it only outputs 4.5v, and so is incapable of powering all three.

 

Good lesson learned by me, hopefully this helps you guys too

 

Cheers

 

Les

[Rapti]

Hello, Les,

your setup looks super exciting. Could you show some more of it? Which components did you use? Which LCD modules were used? Is this a selfmade PCB board? What does the code look like?

 

Your solution looks really good!

[No1sonuk]

Guys, I fixed this by connecting a 5v supply to the VC and GND pins. Lovely clear displays now, and checking the Nano '5v' output showed it only outputs 4.5v, and so is incapable of powering all three.

It's likely the Nano's regulator can't supply enough current.

I'd not be surprised if that's half the problem with the glitching I've seen on the altimeter displays.

[lesthegrngo]

Hi there, glad you like it

 

The LCD modules are 0801 (8 x 1) character modules, these to be precise https://www.buydisplay.com/character-8x1-lcd-display-module-hd44780-controller-black-on-white

 

I used them with some FFC adapter boards and PCF8574 boards from ebay, and my own PCB design. The sketch allows you to show all three LCD modules using one nano, and in fact you could also use it for the rotary encoders and buttons too if you wanted.

 

I can give you all the design drawings in .dxf form if that is any use to you. My fascia was made from laser engraved and cut acrylic, the main backplate is from MDF and the PCB is a double sided one engraved on a little CNC router. The buttons are again laser engrave acrylic

 

This is the sketch for the three LCD displays, remember you have to change the addresses of two of the PCF boards by shorting out two contacts (easy to do)

 

#include <Wire.h>
#include <LiquidCrystal_PCF8574.h>
#define DCSBIOS_IRQ_SERIAL

#include <DcsBios.h>

LiquidCrystal_PCF8574 lcd0(0x27);  // set the LCD address to 0x27 for a 16 chars and 2 line display
LiquidCrystal_PCF8574 lcd1(0x26);
LiquidCrystal_PCF8574 lcd2(0x25);
int show;



void onCmscTxtJmrChange(char* newValue) {
lcd0.setCursor(0, 0);
lcd0.print(newValue);
}
DcsBios::StringBuffer<8> cmscTxtJmrBuffer(0x1096, onCmscTxtJmrChange);

void onCmscTxtChaffFlareChange(char* newValue) {
lcd1.setCursor(0, 0);
lcd1.print(newValue);
}
DcsBios::StringBuffer<8> cmscTxtChaffFlareBuffer(0x108e, onCmscTxtChaffFlareChange);

void onCmscTxtMwsChange(char* newValue) {
lcd2.setCursor(0, 0);
lcd2.print(newValue);
}
DcsBios::StringBuffer<8> cmscTxtMwsBuffer(0x12b0, onCmscTxtMwsChange);

void setup() {
 lcd0.begin(16, 2);
 lcd1.begin(16, 2);
 lcd2.begin(16, 2);
 DcsBios::setup();
 
}

void loop() {
 DcsBios::loop();
lcd0.setBacklight(5);
lcd1.setBacklight(5);
lcd2.setBacklight(5);
}

 

Happy to give you any info you need

 

Cheer

 

Les

[Rapti]

Hi Les, wow thank you for all the info. This will help alot.

[lesthegrngo]

You're very welcome. I was hoping that I could find the same displays out there but with white text on a black background, but have drawn a blank so far. They would look so much better in the CMSC

 

Cheers

 

Les