Do-it-yourself LED matrix If you need a small LED matrix of a non-standard size or shape you can make one on your own by using a development board, LEDs, and current-limiting elements.So let's make a 10x10 matrix with ultraviolet LEDs. In this way we'll get a money authenticity detector.We'll use ECI development board by Velleman, 100 LEDs, and 100 resistors.You may ask why we need so many resistors.We'll be using a 5V power supply so we'll need resistors with 470 Ohms so as to set current of 20 milliamperes through each LED.We'll follow a way of least resistance and just connect all LEDs in parallel. However, in such connection it is necessary that each LED has its own current-limiting resistor.So first we solder LEDs onto the board. To make it more convenient we'll fix each line of LEDs with a scotch tape. Then we can flip the board over and quickly solder all LEDs in one go.First we place LEDs. To make sure everything is correct use a longer positive lead. Unfortunately the layout of this development board does not allow setting 10 LEDs into one row. So we'll have to do with nine. Then we fix them with the scotch tape.Now that our LEDs are placed we fix each row with the scotch tape. We can flip the board over and start soldering. LED leads can be nipped off so that they do not get in the way. So we snap off the last leads and start soldering the resistors.After that we solder the resistors by previously fixing them with the scotch tape. Finally we make the missing power buses. In the end we get such LED matrix. Now we supply power and make sure that all LEDs light up. We set the board into a package and that's it - we have a completed device. In our case this is a money authenticity detector.In the same way we can make LED matrices of different colours for lightshow installations. White LEDs are great for lighting while infrared ones are used in night vision cameras.