After coming to Japan my life has been turned upside down more times and in more ways than I want to admit. Finally after 6 months here I found the time to resume electronics projects. Of course being in another country and not having touched a soldering iron for more than a year added some complications to the whole undertaking.
Determined to resume working with electronics projects I went around Akihabara a few times and returned with all the necessary equipment and quite a few thousand yen less in my wallet. To test the new equipment and to let my hands remember soldering again I set out to create an easy project. In my dormitory some people have signs out of their doors with their names or something representing them as a person. I did not. That needed fixing. And what better way to fix this than an LED sign hanging out of the room’s door? With the background story done, let’s go on to how to create the sign
First of all you need to determine the text/shape that your LEDs will form. After you have done that, draw it on paper and how it would go on a circuitboard (I used a stripboard) and roughly calculate the number of LEDS that will be needed. Once you have that number and you have determined the colours that you will use, visit any of the usual LED calculation tutorials. By giving it the number of LEDs, the voltage of your power source, the voltage drop of each individual LED and the current rating of each LED it can give you the optimal way to connect the LEDs and also the amount of resistance needed. This can save you from a lot of calculations by hand. In the picture below you can see the result of the query in my case.
Continuing if you don’t have them you can now buy the required number of LEDs and resistances to match your power source. For the current example I will write レフいる(need Japanese encoding to read it), which basically means Lef is here/at home. Speaking from experience, I would suggest actually checking each and every one of your LEDs before actually using them, let alone soldering them anywhere. It would be annoying to discover than an LED is defective after you have soldered it on the circuit. Depending on the color and manufacturer of your LED (exact values can be found in the sites I linked above) arrange a small testing circuit on a breadboard and test the LEDs like you can see below.
As I mentioned above I had no tools here in Japan so I had to gradually remember everything that would be needed. This caused the absence of some very essential things I needed such as a free hand tool. Not having one, meant that a contraption had to be made to temporarily hold the circuit. Necessity is the mother of invention as they say.
Of course this was only temporary especially since soldering gun and plastic cloth pins don’t go well together. So a trip to Akihabara later I had a normal free hand tool and was ready to work with it.
You can see that it basically is a mess behind the stripboard due to all the LEDs terminals. But there is no need to worry, it’s easy to organize as we will soon see.
Now let’s take a look back at the diagram so kindly made for us by the LED calculation websites. As you can see in my case what I need to do is connect every 4 LED in series. Then each of the quadruples positive terminal should be gathered together to be connected with the power source and each of the negative terminal needs a 10Ohm resistance. The quadruples should all be connected in parallel. As you can understand this means that you can avoid one burned LED turning of the whole sign. Instead if something happens to an LED then it will only affect the quadruple it belongs to. You can see an example of the first 2 quadruples connection for my case in the picture below. Make sure that you connect the LEDs properly taking care to differentiate between anodes and cathodes properly.
Continuing in a similar way just connect all your LEDs according to the calculator’s results until all of them are connected. Make it easy to differentiate between the terminals of your LED groups since later you will need to connect them all together and link to the power source.
Now the only thing that remains is to connect all the LED groups. In my case it easy to differentiate them since as you see from the pictures I made sure that the negative terminals are the ones with the resistances soldered on them and the positive ones are the only non-cut LED terminals. Now how you will connect them depends entirely on you. I chose a more ghetto way and I do know that this is by far not the best way to connect them but it’s sufficient enough for this project.
That was it! It was easy right? All you need to do now is connect the positive terminal of the LED groups to the battery and the negative to ground. Do not forget to add a switch in between since you will need a way to power it on and off.
For me this project served its purposes and I got reacquainted with soldering after a long time. Feels absolutely great. Of course depending on the place where you intend to use it you should figure out a way to hang/stick/attach it on a surface. Since in my case it’s a door sign I used some twine and hang it outside my door.
Some of the LEDs seem to light up a little less than the others due to the angle the photo got taken from. Normally they all light up the same but depending on the battery’s level some may become less powerfull as time passes and due to the resistances if the battery level is low enough the whole sign will turn off. That’s when you know you gotta change the battery. Here is a close up of the sign.
As I mentioned above due to the difference of angle some LEDs seem to light up a lot less than the others. But in this picture there is one burned LED due to a mistake I made in the soldering. I will correct it later when I find the time for it. For now the sign has accomplished all the purposes I meant it for.
More importantly I hope that the sign along with the tutorial helped you in your endeavour of making an LED sign yourself. You can make any kind of sign with any LED color following this tutorial. I could have used blue LEDs which are a lot more powerfull but also equally more expensive. I did not want to spend more money than needed for this sign hence I went with red and yellow. The color you choose depends entirely on your own design. I wish luck to all of you who try to make an LED sign and if you have any questions about this tutorial or any sugestions/corrections feel free to email me at lefteris *at* realintelligence.net