How do the blinkers work?

A project log for 3 Blink Modification for SAAB 9-5

Activates the blinkers 3 times from just a touch on the indicator stalk for 1999 SAAB 9-5

saabmanSaabman 05/29/2018 at 12:230 Comments

I traced out the blinker inputs to the DICE my premise was that the 12v signal from the blinker switch had to be down converted to 5V for the microprocessor and I intend on using a 5v micro to implement the mod.

The 12V Blinker Activation signal from the stalk comes into the DICE on pins 20 and 44. When 12V is applied to pin 20 the left blinker activates and 12V on pin 44 activates the right blinker.

Inside the DICE pin 44 connects to ground via a 1K resistor. This makes sure the input is off when the blinker is not activated.

Pins 20 and 44 also connect via a 47K resistor to a couple of pins of an 8 input Multiplexer chip (74HC151). This 47K resistor basically handles the level shifting from 12 to 5V it just limits the current sufficiently to prevent any damage to the multiplexer and this provides the ideal spot to detect the blinker activation and inject the 3 second latching signal.

As I dont need to worry about level shifting, current limiting or input protection as its already been done in the DICE i can go for a minimum component count solution. This is still early days in the development but I believe I can do it with one component.

I could use an Arduino board or similar, there is tons of room in the DICE but I can do better than that. For no other reason than I can and its cheap Im planing to use a PIC10F200T E/OT this is only a 6 pin package and has built in oscillator so 2 pins for power and ground 2 pins for left and right and i have spare pins, hmm what else can I do ??

These things are freakin tiny 3.1mm x 1.8mm thats like the size of a grain of rice. Drop it on the floor and its gone .....

Ill glue it to the top of the multiplexer and solder wires directly from the legs of the micro down to the corresponding legs of the multiplexer.

I expect to be able to set the pin as an input which "listens" for the blinker activation. If the blinker activation is only brief say 100ms then the pin will switch from and input to an output and go high for 3 seconds then revert back to an input.

If the other pin detects a signal during the 3 second period that will cancel the timer and revert it all back to listening again.