Last week I had a detailed Arduino tutorial on software pulse width modulation using millis() and micros(). Why? Because I wanted to create a Proper Larson Scanner, with persistence and at least 8 LEDs.
Even though it is a popular project for the Arduino Uno, most Larson scanner tutorials, like my first one, have a few flaws. First, there is no persistence, or tail, to the LED as it moves back and forth. Persistence could be solved by using pulse-width-modulation. The Uno and other 328p-based micros only have 6 Pulse Width Modulation (PWM) pins. And let’s be honest, every project is made better by adding more LEDs. 🙂
If you look at this cover shot of KITT from Knight Rider you will see there isn’t just a single light source. It appears multiple lights are turned on, as well as fading effect. This fading effect creates a tail. Of course, the reason is probably that standard light bulbs were being used back in the 80s. Traditional light bulbs don’t turn on or off nearly as fast as LEDs.
Presenting the Proper Larson Scanner
Knowing that a popular Halloween hack is to add Cylon (or KITT) lights to your pumpkins, I thought it was time for a Proper Larson Scanner. This code example does a couple of important things.
- It implements my “software pulse width modulation.”
- Can be used on all 20 I/O pins of an Uno (or other 328p Arduino)
- Does not use any delay()s!
So if you want to make your pumpkin even more Cylon-like this Halloween, check out this full tutorial on a proper Larson scanner.
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