Rear spoiler control

Projects General Guidance
1

Hi all,

I have been searching the forum and only found one post on controlling the active rear spoiler on a car but it didn't really amount to anything.

My car has a rear spoiler that activates at 94mph and then fully retracts about 45mph and I want to be able to adjust the speed that it operates at. There used to be a system called tail wagger but that isn't available any more. The mechanics shouldn't be an issue as it is already all fitted it would just be writing a code and loading it on to arduino.

Has anyone done this and possibly has the code already? I have help at my work place when it comes to the basics of coding but was hoping someone had already conquered it. My thoughts were using the arduino, powering it from the car 12v supply, wiring in the switch that allows it to be raised and lowered manually and then plugging the board into the original loom to control it raising and lowering round about 50mph.

My questions are is this possible and how would I calculate for the board the speed of the car?????

Thanks in advance

2

So the biggest step for this is interfacing with the car to interpret speeds and then adjust the rear spoiler. I'm guessing your car uses its own uCs to figure out how fast you are going and if the rear spoiler needs to be raised or lowered. This leaves you with 2 separate problems. 1) How do you raise and lower the rear spoiler? What specifically triggers this and how do you then trigger it? and 2) How do you know how fast you are going?.

You'll need to figure out the answers to both of these questions and its not something we can really help with, since it would be specific to your car and Arduino independent. Once you know how to figure both of these out, we can help you with implementation.

3

If you can figure-out how to wire-in a manual switch, you can replace that switch with a relay and control the relay with the Arduino. (Then, you can replace that switch with a "3-way" (center off) switch running into the Arduino. The switch can then select "up", "down" or "automatic".)

The logic is fairly simple. Have you done any programming before?

My questions are is this possible and how would I calculate for the board the speed of the car?????

That seems like the hard part. Every car is different. You'll have to figure-out how to tap into the car's speed sensor or speedometer. If the car has an analog speedometer, sometimes they are electrical and there is a DC voltage that's proportional to speed. You'd have to find the right wires and hook-up a multimeter to measure the voltage at 50MPH. The Arduino has an analog-to-digital converter that goes up to 5V. Since the electrical system is 12V, you'd probably need a voltage divider. (Even if you are getting less than 5V at 50MPH, you need to protect the Arduno from higher voltages.

If you can't do that, you might be able to add a sensor (optical or magnetic/hall effect) to your drive shaft or wheel to count the RPMs. Or, you could use a pitot tube to measure air speed.

My car has a rear spoiler that activates at 94mph and then fully retracts about 45mph...

...to control it raising and lowering round about 50mph.

You'll want to keep some of that concept of lowering it at a speed below the activation speed. Otherwise the wing will "chatter" or continuously move up & down when you drive around 50.

P.S.
If you can't find any useful information about your car's electrical system in a car forum, you might try talking to a "hot rod" or "racing" mechanic... Not your "factory authorized mechanic"... Someone who knows your car but is not afraid of making unauthorized modifications. :wink:

**P.P.S.**Or if you can't get the speed sensor figured-out, how about this option? A manual up-down switch, plus it automatically goes down when you shut the car off? Something like that could easily be done with the Arduino (after you figure-out the up-down relay wiring), or it's simple enough that it could be done with logic circuits (no microcontroller or programming). You could probably even do it with just relays.

4

Right so after some digging today I have found the wiring diagram for the rear spoiler. The spoiler is either automatic once you hit 94mph and fully extends then as you slow down it retracts in 4 stages or you can extend/retract it manually with a two position switch hidden well underneath the dash board.

What I found from the wiring diagram is there is one wire goes from the speed sensor to the back of the clocks and then from the clocks to the spoiler control module that operates the spoiler. The one thing I have not found out so far is if it operates off a voltage proportional to speed. Unless I find that answer out on the internet it is going to be a case of connecting the multimeter on some longs leads and driving to see what happens.

Is this anymore help to someone that can help me.

Thanks