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This circuit is the most complex looking yet, but don't worry, it's actually pretty simple.
The only new concept here is that we're using transistors (the small black pieces with 3 pins and a white N). When we supply power from the microbit to the middle pin of the transistor, it allows the negative current from the LEDs to flow from the left pin to the right pin, acting like a switch. When no more power is supplied to the middle pin, no more current can flow through the transistor.
Since we're making a 4x4 LED grid, we have 4 groups of 4 LEDs, each representing one row on the grid of the final product. Each row of LEDs is powered by their own positive pin on the microbit.
Then, the negative of the first LED in each row is connected to the first transistor, the negative of the second LED in each row is connected to the second transistor, and so on. Finally, the right pin on all the transistors go straight to the micro:bit's ground pin.
This allows us to control both the positive and the negative connections on each LED. The benefit of this setup is that we can individually control 16 LEDs with only 8 pins! The drawback is that in order to turn on just one LED, we need to power on/off two pins which can get quite annoying to code.

Pay close attention to the circuit assembly as this project is a little more complex.

Since this matrix is (4 by 4), you could put it on a t-shirt, a hat, a backpack. It's up to you!

We will be showing it on a t-shirt so it looks more fashionable.

What you'd like to display is up to you as well. Play around with images and animations using if statements and loops

Make sure that you are soldering in a well ventilated area to avoid inhaling the fumes and watch the soldering tutorial video a few times before attempting this project.

Get help from a parent or a guardian when working with a soldering iron.