Programming rapid hazard flashing under hard braking - Mazda CX3 Forum
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post #1 of 4 Old 09-14-2019, 10:44 AM Thread Starter
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Programming rapid hazard flashing under hard braking

In Europe under hard braking by law either the hazard flashers or brake lights flash at a rapid pace, then keep the brake lights on steady and turn on the standard hazard flashers once the vehicle comes to a complete stop.

By EU standards, the emergency flashing lights under hard braking are activated when the braking force is greater than 6m/s2 for passenger vehicles. I came across an emergency braking situation on the interstate where a deer popped in front of the person in front of me. Their BMW activated the brake lights, but also turned on the rear fog lamp as an emergency braking light in a feature called Brake Force Display.

In the States, the two main brake lamps, not the CHMSL must stay lit steadily when braking no matter the force of the braking, however doesn't regulate whether or not the hazard flashers may turn on automatically and temporarily. Some states regulate hazard warning flashers while driving, but not while braking.

There has been a study where rapidly flashing brake or hazard lamps decreased a driver's reaction time in emergency braking situations: Mazda does have this feature, however it is limited to markets outside the US:

Long story short, anybody able to program this into a CX-3 or maybe install a Raspberry Pi with some special coding?

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post #2 of 4 Old 09-14-2019, 08:47 PM
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I installed one of these on my third brake light and it works great.
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post #3 of 4 Old 09-16-2019, 03:25 PM
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This sounds like a job for an Arduino with an accelerometer. Connect an output pin to the CHMSL via an NC relay so that the light stays on during normal braking.

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post #4 of 4 Old 09-17-2019, 12:06 AM
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Originally Posted by NotAPreppie View Post
This sounds like a job for an Arduino with an accelerometer. Connect an output pin to the CHMSL via an NC relay so that the light stays on during normal braking.
This probably, I havent messed around with Arduino but one of the issues with using raspi as a controller mainly due to people having attempted headunit tablet replacements in automotive aspects, is how to handle the on/off cycle. Raspi specifically is basically a tiny computer and doesnt respond too well to forced shutoffs and takes a bit to boot up to whatever settings you set it onto. Operations are the easy part but handling on/off state of the car while having the response time of a generic product from ebay which works with the car once its wired in makes it hard and discouraging to go that route.

The other route is to permanently hardwire it to the battery/always on current which is gonna be a drain however slight it may be and isnt recommended.

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