Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Driving (9x 4digit) 7-segment displays. (12x3 digits)

Status
Not open for further replies.

Panici

New Member
Bear with me, this my first project.
Please include details that are assumed knowledge to an experienced person.


I'm planning to build an external display for PC racing simulators (ie. rFactor)
Mock up:
**broken link removed**
The plan is to build on breadboard then transfer to perfboard at a later date.


I'm going to use 9x red 4-digit modules (0.56") from here [12 pin version]:
https://www.kingbrightusa.com/category.asp?catalog_name=LED&category_name=KC4-Digit+0.56in&Page=1
Should I get Common Cathode, or Common Anode?


My main concerns right now are:
1. Power - How to physically wire power to all of the displays. (using a 5v bench supply most likely)
2. Data Transfer - How to get the data from the arduino onto the displays. (multiplexing? hardware/pin wiring?)
3. Fast display refresh rate/speed - I've seen displays lag with only four 7-segment displays, so i'd rather use extra pins on the Arduino then daisy chain.
4. Special characters. - In addition to (0-9,A,B,C,E,F) Ideally I want to be able to use the segments to form whatever other letters I can. (n, r, o, d, b, etc)


Oh and also, while talking about speed, I plan on also driving two (possibly 3) of these using the (TM1638) library.
**broken link removed**

Let's leave the TM1638 based modules out of the equation for now, unless we need to somehow wire them together with these displays, in order to not have display lag???

I obviously cannot drive (9x12) pins right off of the arduino, so what is my best option?
 
How many Arduino pins can you dedicate to driving the display?
 
I'm using an Arduino Mega, which has 54 digital IO pins.

I'd say using 40-45 for the display is reasonable.
 
Let me recommend a MAX7219 chip if you go for common cathode displays. Each chip can drive eight digits and handles the multiplexing timing autonomously, so you'd need six of them (two per display row) to keep it tidy. I'd been wondering what using them to control a whole bank of 7-seg displays would be like (eg an Apollo flight computer display) and this is it!

I bought some on ebay and they're cheap and easy to use. You clock the data into them serially and each digit is one internal RAM byte. You can use the internal seven segment decoders or choose to override any digit with a segment pattern of your own. It contains current drivers and uses one resistor per chip to set the segment current but you also have digital brightness control. You can also use them for dot displays up to 8x8 and I have done so with success.
 
Last edited:
Yep, I'm sure there's a lot of choice. Out of those three I'd still go with my low-parts-count (six chip), low-cost MAX7219 suggestion over those other much older single digit driver (ie high-parts-count: 36 chip) alternatives providing he's happy to use common cathode displays and go for a multiplexed design.
 
Last edited:
Yes that's a nice alternative - if he hasn't got his mind set on 7-seg display.

"You will not have to constantly scan the LEDs"

.... same with the MAX7219 which does it for you as I said, unlike those 4511 and 7447 single digit drivers.

Anyway, the OP asked the question six months ago so he probably decided by now.
 
Last edited:
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top