This board is a tester that can be used to test LEDs connected to larsskj-003 boards. It utilises a small IC called NSI50010YT1G for current regulation instead of resistors which guarantees a constant current of around 10 mA no matter the supply voltage. If you prefer, you can use SMD resistors instead, but this will limit the voltage range considerably.

PCB layout

The NSI50010YT1G may not be very well known as it's a rather new circuit. It's meant to be used in car LED lighting and is a low cost IC, making it well suited for purposes like this tester. Using this IC means that you can use supply voltages from 5 V to 50 V and yet get the same current and same amount of light from your LEDs. It's rated to supply a fixed current of around 10 mA.

An IC like this is of course a bit more costly than resistors, but it's still a low cost circuit: You can build the entire tester for less than $5.00 in components if bought wisely - excluding the PCB.

U1-U8 are used to supply current to the primary LEDs, whilst U9 is used to supply D1 which is a power indicator. If you do not want that, you can simply skip U9 and D1.