DIY, Flasher, LED, LED DIY, Turn Signal, Write Up -

Full Flash

What I refer to when I say full flash is a circuit I designed to change the way the typical flasher bulb operation works. Instead of the running light staying on during the duration of the flash signal I installed a circuit that allows the light to shut off the signal for the running light while the flash signal is turned on. 

This is done by using a small microcontroller called a ATTINY85 which I program via a Arduino board. Which is a small development board that can be used as a programmer for the ATTINY85 controller. The ATTINY85 controller allows me to program a custom PWM (Pulse width modulation) I prefer to use this method to dim the lights instead of the using two series of set value resistors. Main reason being the reason is that through an input on the microcontroller from the flash pulse signal I can shut off the output for the PWM and get the desired look I want as well as having extra IOs I wll be able to further add features if so desired. 

How do we know how much contrast to set the turn signal to on full power vs running lights is pretty easy due. We know what the watt outputs are for a standard 1157 bulb and its generally about 20w for high flash signal and 5w for running. When you combine the two you get 25w because they will both be on when the flasher is on. So that means we have a total of 25 which 5 being the running power so 20% is about the duty cycle we will need to set the lights at. 

So in turn the main idea of how the events take place are 

  1. Running lights turn on
  2. ATTINY85 Powers on and sets PWM to about 20% duty cycle which in code because it is based on a 256 value is about 51 give or take depending on the amount of light that is produced by the specific LED Array at that duty cycle. 
  3. When the Flash signal is activated it triggers an input on the controller that uses the pulse oh high and low to set to then turn off the PWM signal and the flash signal comes direct through the board to power the lights directly through a voltage regulated circuit (at least on the first generation of board it is a voltage regulated circuit) 
  4. Once the pulsing signal has stopped the controller waits 1 second to then turn back on the PWM to the continue operating the running lights.


This is the standard operation of the full flash circuit in very light detail. Later there will be a post going over the control circuit.

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