Where a big LCD display for an arduino

grimreeper132 · October 23, 2017

I want to get a big LCD display so I can display messages on it, long story, and I am pricing out the cost of it. I can have an external power system for it. It will need to be 1.5m by 0.5m in size and be able to be controlled off an arduino preferably (other could be done, but arduino would be the best.) Something like the image below, only needs to display 1 (maybe 2) lines of text.

Zagna · October 23, 2017

Do a 3x2 of p7.62 smd red color led module 244*488mm?

You can find a number of dot matrix signs on AliExpress and the like.

Or a 5x3 of P10 led display module 160*320mm?

MadModder · October 23, 2017

1.5 meters? X .5 meters? or am I reading that wrong?

You're going to have a hard time finding an LCD screen that large, that isn't a monitor, and that is an odd aspect ratio for a monitor. I know they make programmable LED signs that large, and probably with that aspect ratio. I would recommend a google search of commercial signage companies. Be prepared for this to be expensive, unless you can find a used one.

mariushm · October 23, 2017

You won't find a LCD display of that size.

LCD is based on liquid crystal - the display in the picture has individual cells of that liquid crystal - when a controller on the back of the display sends power to that cell, the liquid crystal becomes opaque so the dot becomes black and you can see it because of the green light which creates the contrast.

The controllers behind these lcd panels can only drive something like 160 x 32 "pixels" and it's possible to connect two such chips to have larger surfaces like 240x64 pixels but nowhere near the amount of pixels you would have in 1.5 meters by 0.5 meters.

To go that size, you'd have to use LEDs to create each pixel.

On that LCD display in your picture, each character takes 5 x 7 pixels ... if you were to make your own display, it would be easier to make each character use 5 x 8 pixels because then every time you want to display a character, you'd send 5 bytes to the display ( 5 x 8 bits, one for each pixel in a vertical line that forms the character

If you go with two rows of characters like the display above, you'd need to have at least one line of empty space between the rows.

So in total, let's say we have 2 rows of 8 pixels vertically , then we leave 2 pixels worth of space between the rows and let's have 1 pixel worth of space at top and bottom of the display to make it a round 20 pixel vertically.

In 0.5 m height or 50 cm, that would mean that each pixel would use 2.5 cm of space, or almost 1 inch (2.54 cm)

You'll want square pixels, and each character uses 5 pixels horizontally, but there's one pixel of space between characters so each character actually uses 6 pixels. Therefore, in 1.5 meters (150 cm) , you'd be able to create 150 cm / 2.5 cm = 60 pixels, which works out exactly to 10 characters

So your 1.5 meters by 0.5 meters would be 10 characters x 2 rows

If you want it to be 16 characters x 2 rows, it would have to be 16 characters x 6 pixels per character x 2.5 cm per pixel = 240 cm x 50 cm

If you're stuck with maximum 1.5 meters and you want 16 characters, then you'd have to restrict the pixel size to 150 cm / 16 characters / 6 pixels per character = 1.56 cm ... so you'll go with either 1.5 cm squares or 0.5" (1.27cm) depending how you're more comfortable.

With 1.5cm digits, you'd have 144 cm plus 6 cm of border in width , and 20 pixels x 30 cm in height

OK, so now you have you have 16 x 2 pixels , each character is made of 6 x 8 pixels... so you have 16 x 8 = 96 pixels horizontally and 16 pixels vertically. You'll probably want to put pixels even where there's empty space between characters, as maybe you'll want to make scrolling text or various effects in which case it would help to have all 6 pixels for each character. I'm assuming you won't need to put leds between the rows, since it would make the design easier.

Since everything works easier with multiples of 8, we can nicely split this 96 pixel by 16 pixel into 16 x 16 pixel blocks, and we'll have 6 x 16 x 16 displays.

The easiest would be to have a led driver and a microcontroller (arduino nano , a pic, whatever) on the back of each of these 16 x 16 blocks. The microcontroller receives from your arduino 32 bytes (32 bytes x 8 bits in a byte = 256 bits, 16 x 16 pixels ) through i2c , uart. The led driver can turn on or off as little as 8 leds or up to 32 leds but the most common led drivers will easily drive 16 leds.

So the microcontroller will loop through each column of leds or horizontal lines and for each of the 16 of them, will tell the led driver which leds need to be turned on or off and then send power to that line or column for a period of time (let's say 10ms), then it will turn off the line or column, and tell the led driver which leds should be on or off in the next row or column and then turn on that line and loop through each line/column until new data is received.

You can also program that tiny microcontroller to pass the data to the next microcontroller by connecting the 16x16 sections together, and only update the characters when your arduino sends a signal that says "update now" , this way your arduino can send 6 x 32 bytes to the first 16x16 panel and the fist panel will pass the bytes to the next and so on.

grimreeper132 · October 23, 2017

41 minutes ago, MadModder said:

1.5 meters? X .5 meters? or am I reading that wrong?

You're going to have a hard time finding an LCD screen that large, that isn't a monitor, and that is an odd aspect ratio for a monitor. I know they make programmable LED signs that large, and probably with that aspect ratio. I would recommend a google search of commercial signage companies. Be prepared for this to be expensive, unless you can find a used one.

it doesn't need a high res it just need to be that size so you can read it from a distance

2 minutes ago, mariushm said:

-SNIP-

I would like one big screen doesn't need to be a LCD if its not practical, but I need it to display a message, so yea

45 minutes ago, MadModder said:

1.5 meters? X .5 meters? or am I reading that wrong?

You're going to have a hard time finding an LCD screen that large, that isn't a monitor, and that is an odd aspect ratio for a monitor. I know they make programmable LED signs that large, and probably with that aspect ratio. I would recommend a google search of commercial signage companies. Be prepared for this to be expensive, unless you can find a used one.

that's what I was thinking of yea I would do, any cheap, big ones you can see as most I can see are small and cost about £30 min (budget is not massive)