We had many ideas like a smartwatch or smart mirror in the beginning, but it became clear it was better to build a Led Matrix you could use to display anything you wanted. For example time, date, weather info, notifications or have a site where anyone could leave messages and display them at wall at college. We finally settled on making it more engaging by programming the retro game pong on it. This way it would show off nicely what Iot is about: "Controlling and monitoring anything from anywhere in the world".

The Matrix

The matrix was build in my basement on a home built table saw made form a wooden board and a circular saw. I bought two large pieces of lumber to be cut in thin strips and frame as it would been very expensive to buy the thin strips separately. They are about 900x30x3mm and have a 3mm slot where the other gird piece slides in.

The the Led strips arrived from aliexpress they where about 40€ for 10m (30 leds per 1m).

I tested them out by using a test sketch to turn orn different colors. And they seem to work beautifully.

So now I could cut them into 80cm strips which works out to exactly 12. The grid will be 12x25 pixels.

The adhiesive seemed to be strong enough to keep the strips comming of of the particle board. But I'm not to worried about them comming of because in addition the grid will be keeping them in place.

Now the ends had to be soldered together, which was a bit tidious but it got done in a half an hour.

I made sure that + was conected to + and - to - and the data out of one strip to the data in of the next strip in a "snake" configuration, which saves wires and time it can be compensated for in the code later.

After a lot of fiddeling the grid was complete. A nice thing is that it holds together just by friction cause by my inaccurate work :) But some pieces got chipped of by the saw, which i glued paper over so stop the light from bleed into the other cells.

It can be lifted out of the frame esasily if repairs are neccessary.

For a nice touch i rounded of the side pieces with a router and a round bit, but before that holes had to be drilled to srew the frame together. No glue is use in the intire build which makes it easy to dissasemble.

Time for the firs tests.

The firs scetces I did were simple one liner color set methods.

I tried diferent colors and brightnesses to see how bright it would be with just the usb power.

In theory each led uses 100mA, I have 200 leds wich equates to 30A! of power usage. So I will ad a bigger power supply later.

Old Pc power supplies are great for this application as they can proivide up to about 40A on the 5V rail.

The Code

It turned out to be the bulk of the work as we had to use javascript for the website and I had never coded in js before luckily there is W3Schools wich taught me everything I needed to know.

More to come...