when there is no connection to the left turn input i e when the turn signal is off r 5 is a current limiting resistor for voltage spikes entering through the left turn input d 3 and d 9 limit the noise voltage to ground or 5 volts depending on the polarity of the noise current the power supply circuit is described the power is connected to the circuit between ground u2212 and the anode of d 2 d 2 is present to provide polarity protection for the entire circuit if the power connections are reversed no current can flow to the circuit since d 2 is reverse biased c 2 provides filtering for the input current u 1 is a three terminal regulator that regulates the input voltage 9 to 16 volts to 5 volts the 5 volts is supplied to all points in the circuit requiring 5 volts c 1 is an output filter for the 5 volts fig3 the freestanding flasher unit is designed around a single chip 8 bit microprocessor the processor used in the prototype is a microchip pic 12c508 microprocessor however there are dozens of other 8 bit processors that could be used for this purpose pin connections to the microprocessor up are as follows the up performs logic operations based on time to create the flashing output from the flasher unit for the purpose of a prototype design the emergency flash output is a series of flashes as follows on 75 ms off 150 ms on 75 ms off 150 ms on 75 ms off 150 ms on 75 ms off 525 ms repeat every 1 275 seconds this sequence may any other combination of repeating or non repeating flashes the unit is activated by.