Harry's GPS Suite Forum

Would be great to capture the brake light from OBDII (if thats possible) and use it to show when the driver is braking.

Braking is no standardized OBD data and not available. On the other hand, negative longitudinal acceleration is a very good indicator for hard braking.

- Harry

Yes I was wondering about this feature the other day aswell. One of the guys in our club runs a vbox light and as far as I can tell he's doesn't have special brake sensor, yet his video's show braking indicators. He swears blind all his info comes from the obd.

Maybe they have some kind of braking overlay function worked out from the G Force.

http://www.youtube.com/watch?v=6xA7cZvi ... e=youtu.be

Would be an excellent feature to have.

Cheers

Paul

Negative longitudinal acceleration = braking.

Harry

I would bet a small amount of money that the braking indicator lights up when he gets off the gas without pressing on the brake pedal. That is, it reflects a reduction in speed, not actual application of the brakes.

Harry,

Would it make sense to put a braking indicator into the video output that estimates the braking force based on the movement detected by the g-force data?

Sense yes, but I'm not yet sure it produces correct results for all kinds of cars / configurations. Two issues that need to be solved:

1. Not every negative acceleration is braking - think of rolling down a hill at constant speed. Most probably this can be worked around as the scenario is unusual on track It will be necessary to look at typical braking / longitudinal deceleration patterns to catch the right position braking started (and not detect "roll the hill" at all). Actually I need to get that pattern recognition stable because many users test LapTimer on public roads and would wonder what is going on when "rolling the hill" is detected as braking... (I have dozens of bug reports on acceleration calibration not working - because some users try this driving down the start / finish straight and break hard when approaching a traffic light... This certainly does not generate the same forces like in track).
2. Detecting 100% braking or "full braking" will require some kind of calibration. Cars can achieve quite different negative longitudinal forces when breaking - depending on grip, wheels, weight, brake quality etc).

I will think about. I case anyone wants to contribute some math or typical values that appear during braking, please share.

- Harry

My car has on board telemetry that shows brake pressure iirc.

I'll take a pic later. I did ask for this feature some time ago my self with the throttle bar either red or green to show braking/throttle although thinking about it it would need two bars for toe/heel technique and would need to come via the obd for that reason.

Most modern cars have brake pedal information available on the bus. However, this information is not available from the standardized OBD II protocol - it is not emission testing relevant. If I remember correct we had a thread on this somewhere already.

- Harry

Yes it was me who asked a few months ago about this.

Anyway here is what my car info shows on its display

Pedal not depressed



Pedal pressed down