Why has my car’s turn signal never synchronized perfectly with any other car’s signal literally ever?


Why has my car’s turn signal never synchronized perfectly with any other car’s signal literally ever?

In: 9

Turn signals are older than modern digital systems. Your turn signal bulbs draw power, that power creates a little heat inside the flasher module. This breaks the connection. Then it cools, and it makes the connection and they light up again. Over and over. Different bulbs and other factors will cause it to flash at different rates. So the timing isn’t perfect and varies from car to car.

Like everything else, they’re digital now, and have perfect consistent timing now. It’s going to become more and more likely to see perfect sync between vehicles, given that you both started your flashers at the same time.

But also… You’d have to have the same make and model to guarantee it syncs.. because there is no standard timing! There is only a range specified by law, not exact timing. So different makes and models use different timing.

Mine did once…one time out of hundreds of thousands. I still remember how awesome it was.

If you sit at a red light long enough and focus on one particular car, your signals will eventually sync. Maybe only for a couple of blinks because they’re not flashing at the same speed, but it’ll happen. Otherwise, there are many factors affecting why it doesn’t happen. The simplest is that most manufacturers use different modules to make their signals flash. A Toyota and Ford might be off by milliseconds, but that in itself means they will never sync perfectly with each other. The other big factor is that everyone turns on their signals at a different time. If you and the car next to you (of the same make/model) flipped on your signals at the same exact second, then it might be perfectly synchronized.

I used to sit at a turn signal that took two minutes to turn green every morning on my way to work. Thought long and hard about this, apparently.

A relevant video is on [Technology Connections!](https://youtu.be/2z5A-COlDPk) I didn’t read any other comments, so perhaps it has already been answered, but this guy’s videos are far more interesting than they have any right to be.

There are a few things to consider. Older cars use a relay to operate turn signals which work by passing electrical current through a piece of metal until it heats up enough to expand and disconnect the circuit, which then reconnects when the metal cools down and shrinks. Imperfections in the material and manufacturing process and variances in electrical current from car to car makes these relays almost impossible to synchronize.

Also, even with newer digitally controlled circuits, timers aren’t always 100% perfect. Crystal oscillators will have a small percentage of tolerance in the actual frequency in which they oscillate. They will also be affected by stability of source power, temperature, and other small factors. You can have a hundred oscillators that are specified to operate at 32,768 hertz but, in reality, may vary by hundreds of Hertz between them. Though the effect is minimal in most uses, over time it will cause desynchronization. Software controlled lights, which use processor clock speed for timing instead of a crystal oscillator, can cause desynchronization when the processor cannot complete instructions within specified time which cause them to delay in response to other requests. This phenomenon is known as clock drift. This is why GPS timing, as GPS satellites use atomic clocks to provide timing, is important in synchronization sensitive applications, like long distance point to multipoint microwave radio communication or to provide “authoritative time” for logging.

There’s also the fact that people don’t turn on their turn signals at the same exact time.