# How do you make a 12x1 LED Matrix?

Hi everyone,

I'm completely new to this site as well as DIY projects so I would love some help on a uni project I am currently trying to start. My idea is to make an abstract clock which only contains an hour hand only and the clock face itself will rotate to tell the hour. The hand will be made up of a 12x1 LED matrix. Each light is supposed to represent each 12th segment of the clock and will light up when it is past that segment in time. For example, at 3:15, the clock face will have rotated so the hour hand (that always points up) points on the 3 and 3 out of 12 LEDs will be lit. This has to be programmed with an Arduino.

Being new to physical computing etc. I am so stuck on how to even begin this project! If anyone has any ideas of how I can begin this please let me know! Or just help me get started by telling me how I can make a simple 12x1 LED matrix to act as the hour hand. I look forward to your replies, many thanks everyone!

steveastrouk7 years ago
12 x 1 isn't a matrix, 3x4 or 4x3 or even 2 x 6 is a matrix. If you are stuck for I/O then consider a matrix, otherwise, try the Allegro A6282 chip - it'll drive 16 LEDs, and control the current to them all, with only two or three control lines from your processor.
mathews7 years ago
You will need a reliable clock signal which will trigger once an hour.

The CMOS 4040 will control which LED is on. It's output should be connected to transistors driving the LEDs.
origamiwolf7 years ago
The straightforward way is to dedicate one arduino pin to each LED.  Wire up a current limiting resistor (~300 ohms or so) in series with the LED, stick the plus end of the LED/resistor into one arduino pin, and the minus end goes to a common ground.  You'll have twelve such sets of resistor/LED pairs, each of which is associated with one arduino pin.  Set the arduino pin outputs to high or low to turn the LEDs on and off.

It's not a terribly efficient use of pins, but if you have enough arduino pins to spare, it's an easy way to go.

Otherwise, you'll either need to consider multiplexing methods (many instructables on this already), or using external hardware like LED drivers and shift registers.
gmxx7 years ago
a 12x1 led matrix would be 12 leds. not that special.

you can use led bargraphs to make a better looking hand, but i have only seen 10 or 20 led versions, so you would need to cut one down to size.