Dimmable LED | RaspiKidd

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Overview

In this tutorial we're going to use the and the on the board to make a dimmable lighting system.

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What you'll learn

How to control the RGB LED using the potentiometer.

What you'll need

PicoBricks
Raspberry Pi Pico
USB to MicroUSB cable

What you'll need

Potentiometer

A potentiometer is a knob or dial that controls how much electricity flows through a circuit. Think of it like a tap for water: turn it one way and more comes out, turn it the other way and less comes out.

Real-world example: A volume dial on a speaker is a potentiometer, turn it up for louder sound and down for quieter.

RGB LED

An RGB LED is a tiny light that can glow in any colour you like. It mixes red, green and blue light in different amounts, a bit like mixing paints, to make all sorts of colours.

Real-world example: Like the colour-changing lights some people put behind their TV, an RGB LED can shift from red to green to blue and everything in between.

Variable

A variable is something that can change. Think of it like a labelled box: you pop something inside, and the label tells you what it is. You can swap what's inside whenever you like.

Real-world example: A variable called score might start at 0, then change to 1, 2 and 3 as you collect points in a game.

Forever loop

A forever loop repeats its instructions again and again without ever stopping (until you switch off or reset). It's perfect for anything you want to keep happening over and over.

Real-world example: Like a clock's second hand that keeps ticking round and round, a forever loop keeps running the same steps over and over.

Set up your PicoBricks

Connect the PicoBricks board to your computer using the USB cable.
Open your favourite web browser (we recommend Google Chrome or Microsoft Edge), go to ide.picobricks.com and select PicoBlockly.
Connect the board to the coding environment by selecting the connect button at the top of the code area.

The PicoBlockly coding environment

Build the code

Select Basic. Drag a PicoBricks block into the code area.
Select Loops. Snap a forever block onto the `PicoBricks` block.
Select Variables. Select Create variable and type Colour. Snap a set Colour to block inside the forever block.
Select Math. Snap a round block onto the set Colour to block.
Select Math. Snap a 1 + 1 block onto the round block, then change the + to a x.
Select Bricks. Snap a Read Potentiometer block onto the round block, before the x sign.
Select Math. Snap another 1 + 1 block onto the round block, after the x. Change the first 1 to 255, the + to ÷ and the remaining 1 to 65535.
Select RGB LED. Snap a Set RGB Led Colour R 255 G 255 B 255 block under the set Colour to block.
Select Variables. Snap a Colour block into the R value of the Set RGB Led Colour block.
Do the same as step 9 for the G and B values.

The completed dimmable LED code

Run it and Watch

Now the code's finished, let's test it. Select the Run button at the top of the code area. Turn the potentiometer to see the LED get brighter or dimmer, right down until it goes out, depending on which way you turn it.

The dimmable LED fading up and down as the potentiometer turns

Try it yourself

Challenge: Can you make your dial control just one colour? Try setting the G and B values to `0` and leave only the R value linked to the potentiometer, so your knob fades a red glow from bright to off. Then have a go at swapping it to just green, or just blue. What happens if you mix two colours together?

Stuck? Quick fixes

Problem	Try this
The LED doesn't light up at all	Check PicoBricks is connected using the connect button at the top of the code area, then press Run again.
The brightness doesn't change when you turn the dial	Check your `Read Potentiometer` block is inside the `round` block, just before the x, and that the maths reads `x 255 ÷ 65535`.
The colour looks wrong or flickers	Make sure the same `Colour` variable is dropped into all three slots (R, G and B).
PicoBricks won't connect	Try a different USB cable or port, check you picked PicoBlockly, and press the connect button again.