The MX-5 turn signal clicking sound is very quiet. Often times when driving with the top open, it’s easy to forget to turn it off. There are a few discussions and solutions on the Miata forum about this issue. Some solutions that are available on the market require permanent installation with taping car wires.
I decided to make an audible reminder as a plug-n-play module utilizing an OBD port. Because all the car status messages and warning beeps are accessible through a CAN bus, this is the best option, in my opinion.
By reusing my previous boards with CAN microcontroller, I made a very quick prototype.
In this implementation, a warning beep is produced by a buzzer located inside the Instrument Cluster, initiated by a CAN message. I chose a 4 short double beeps option. It is the same alarm sound as when you are trying to lock the car with the key inside. Kind of a gentle reminder.
My implementation starts a 40-second timer, only if the car is in motion (above 2mph). This will avoid unnecessary beeping when waiting at an intersection with the turn signal on.
After 40 seconds on the move with active blinker, it will beep 4 times and wait another 40 seconds, and so on.
I designed a simple 3D printed enclosure. My module is now ready to hit the road!
The location of the OBD port in this car is perfect for a footwell light, as well. I decided to integrate my timer with an LED light. Utilizing the CAN bus, I can get the status of door action, so as soon as the door opens – the light goes on. When the door is closed – the light slowly fades to off. And again, there’s no need to tap any extra wires, like in other available solutions. The OBD port has a nonswitchable power source. There’s no need to start the car to activate the light. The microcontroller has a power-saving sleep mode. As soon as the CAN message stops it goes to sleep (consuming less than 1mA), and it wakes up as soon as CAN activity starts, which is activated by opening the door or pressing buttons on the key fob.
The next step is to design a production-ready board and a more slick enclosure.
After testing this device during driving, I realized that 40 sec. timeout is way too long, so I reduced it to 16 sec. The beeping sound is still too quiet, especially if the radio is on and the top is open. To make it more noticeable, I decided to use constant beeping, until you actually turn off the blinker.
This device is available in my store.
Discussion on Miata forum is here.