Introduction: Moped Mod:Turn Signals+Under Body Light+Brake Light

About: Awesome Electronics Tutorials, Projects and How To´s

In this project I will show you how I modded the lighting system of an old Moped (Simson S50). The old bulbs and flasher relay are just inefficient and not reliable. I added LEDs to the turn signals and brake light. Everything is controlled by the awesome Attiny85. As a bonus I also included under body lights in the circuit. Let's build it!

Step 1: Watch the Video!

This video gives you a basic idea how I changed the lighting system of the moped. But since it is kind of complex I will go through the most important steps again.

Step 2: Order Your Parts!

Here I present the parts that I used. Of course you can change the number of used LEDs, but that would mean you need to look for other resistors. Just use this list as a recommendation by me (affiliate links):

58xRGB LEDs (common Anode):

32xOrange LEDs:

8xWhite LEDs:

3x10kΩ, 2x1kΩ, 1x56Ω:

1xLM7805 (5V linear regulator):

2x10µF Capacitor:

1xArduino Uno (as programmer for Attiny85):


1xIC Socket:

1xPCB (striped, we used one of those for the big resistors) :

1xPCB (copper dots, for the controller board):

1xBC140 NPN Transistor:

3x12Ω 5W:

1x19Ω 1W:

1x8Ω 5W:

4x5.6Ω 5W:

1x47Ω 1W:


Silvered Copper Wire (Bridge Wire):


That is quite a long list. But it will be worth it in the end!

Step 3: Build the Turn Signals and Brake Light!

We used veroboards with stripped copper traces for the turn signals and brake light, because it is easier to connect parts in parallel this way. We used a dremel and rasps to give them a custom size. This way they will fit perfectly in their cases later. You can decide how many LEDs you want on each turn signal and brake light. We chose this constellation:

Turn Signals (4 of those):

4xorange LEDs (front and back)

2xwhite LEDs (only front)

1x RGB LED (front and back)

Brake light(only 1):


All of the anodes must be connected in parallel. And the cathode of each color. At the end you need to solder wires to each cathode and the common anode.

Step 4: Build the Controller Board With the Attiny85!

Here you can find the schematic of the whole lighting system. This includes the circuit for the Attiny85. It is a pretty simple one with a 5V voltage regulator (LM7805) and a few pull down and one pull up resistor. I used a veroboard with copper dots for this one, because I was able to build the circuit really small.

Step 5: Upload the Code to the Attiny85!

Here you can find the code for the Attiny85. I like to use an Arduino Uno as a programmer. If you don't know how this work then take a look at my other video:

Step 6: Mount All the Parts on Your Moped and Wire Everything Up!

The title says it all. You can put your switches wherever you want and don't have to use the same technique that we use. Just follow the schematic and everything will work out in the end.....hopefully!

Step 7: Success!

You made it. You just modded your own Moped. Whether this is street legal is another question, but still pretty awesome!
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