Party LED-lights for our double-decker bus

We have this crazy tradition in Norway.

It’s called “Russetid”.

The time just before the final exams at high school, the students embark on three weeks of partying. Everyone gets a crappy old car or a bus, just for partying in it for three weeks.

It’s been a few years since my “russetid” now.

But back then, me and a group of friends chipped in to get an old London double-decker.

We worked on it for months to get it ready for “Russetid”.

One of my projects was a LED chaser.

A LED chaser is LED lights connected in a line, with only one LED turn on at any given time. It makes it look like the LED light is “running” along the line.

(When I am writing this, I get the feeling that I have recently written about it. But anyway…)

I connected the LEDs in the roof inside the bus, and tested it with a 9 V battery.

It worked beautifully!

All my buddies were amazed of the cool lights I made for the bus.

Then, one of them asked me if I could also make them be on all the time, without the “running” effect.

Being a bit high on myself after all the praise for showing off the running lights, I said “Of course!”.

…the truth was that I didn’t really understand much, I just built this circuit off of a diagram I found on the Internet.

But the party was about to start, so I had to do something quickly.

I connected all the LEDs in parallel and connected them to the 9 V battery.

All of them lit up. Woho!

The last thing to do was to switch to the 12 V battery in the bus, instead of the small smoke detector battery.

The line of LEDs was laying on our seats while I was working on it.

I was a bit stressed because I knew that in a few minutes, people would start to show up, and I wouldn’t be able to work on the lights anymore.

So I took a chance, and just connected the 12 V bus battery directly to the LEDs in parallel, hoping that it would all work just like that.

But no.

The LEDs lit up really bright for half a second, then smoke started coming from the seats.

I quickly disconnected the 12 V battery again, but it was too late.

The LEDs had burned small little holes in the seats, and the LEDs were all broken.

I had put too much current through them.

Back then, I didn’t understand the concept of using resistors to limit the current in a circuit.

The 9 V battery worked because it wasn’t able to deliver enough current to burn out all of the LEDs. But the 12 V battery in the bus was much more powerful.

The circuit was broken, and I was too disappointed to make a new one.

So we had to party without my cool lights.

I want you to learn these small things that make an impact in a circuit. That’s why I have spent the last period of time, upgrading my eBook «Getting Started With Electronics».

The last weeks I have been saying that it’s just around the corner. And it is! It’s just that things tend to take longer than planned.

But you can get the current version in the following link – and get an automatic free upgrade to the new version when it’s released:

https://www.build-electronic-circuits.com/products/ebook-2nd-edition/

Keep on Soldering!
Oyvind