In the data files of my Cup car I would like to see when I actually start pushing the brakes. I know I could/can do this using a math channel on my deceleration g's but it would be nice to have something precise. I've heard about using an extra channel on my EVO4 logger that I could simply wire on the brake lights? So when the light goes on ( = you pressed the bitch pedal) it stores it in the logger (basically an on/off channel).

What kind of connectors/pieces would this require?

 

Use positap connectors on the brake light wires.

 

I was just wondering if I could use the power that goes to the brake light directly, or if I need extra stuff to make sure that the EVO doesn't receive more than 5V. Don't want to blow that thing up, it's quite expensive

 

This is what I found in a doc:

EVO4 acquires:
5 analog inputs, at a configurable frequency from 1 to 1000 Hz per channel. These signals can be: 0-5 Volt, 0-500 mV, 0-50mV, thermocouples K.

 

I don't think you can put the 12v into the Evo4. You would have to do a relay with the relay switching the 5 volt signal on/off.

 

It's a single wire on the ground of the brake light to a digital input. If I remember correctly, it's been a while.

 

I got rid of my post because Matt is correct, no 12V is allowed in CH1 through CH5, but you need to find out if the 996 brake switch is switch on=complete circuit to ground. Or you could do it through a relay, easy because you just complete the circuit to 5V vRef to signal in and then you're set.

There are many ways to do this, it is valuable and worth doing if you don't want to add a brake pressure sensor.

 

I could also tap the 12V wire and put a 12V-5V converter between and go to the EVO4 from there, but maybe a relay is a better idea.

 

This was driving me crazy, I couldn't remember if it was MoTeC or AiM that we did this with a million times. The answer was, we did it with both. I pulled up the dash configs we have in archive for Evo4 and MXL's.

For AiM, in a Spec E30, SPB, and a few other cars the way to do this is to use an analog channel. Use generic linear 0-5v @ 2Hz. Wire pin #3 (+VB) on any free analog channel to the positive on the brake light.

Go ahead and test it first. Trust but verify right? ;-). Take your multimeter and put it on negative at the brake light, then hit the brakes.

Hope this helps.

 

I also emailed the folks at AiM to confirm. Seriously, it's driving me crazy, this was the very first type of connection we did to any car.

 

Ah, made mistake in what I said, should be hot side... (I corrected it above).

From AiM:

 

I found that you can quite easily go from 12 to 5 V by dismantling some random USB cigarette lighter car charger and using the electronics (opened one and it is pretty straightforward it seems).

And being the complete noob that I am (and by noob, I really mean NOOB), where should I start looking to find that wire? Anyone got some schematics to see how to access that wire? I opened the engine lid but didn't see much there. Maybe I need to remove the rear bumper? Or Can I access the correct wire somewhere in the front part of the car?

The problem is that I'm always scared of screwing things up, but if I never do anything myself I guess I'll never learn doing something myself ...

In theory it sounds simple:
- find brake wire +
- take an AiM cable and connect the input voltage pin to a wire to connect to the brake wire + (do I only need to connect 1 of the 4 wires? No negative that I need to connect to the chassis?)
- use some kind of positap connector to connect both
- route the AiM cable through the car
- program and test

In practice it always seems like mission impossible for me once I sit next to the car.

Well, maybe it's not a surprise, coming from someone who doesn't understand why you don't get electrocuted in your car while the negative part of the circuit is wired to the chassis

I m more at ease replacing brakes and cleaning wheels


So any suggestions, tutorials, links to help me out a bit?

 

Don't worry about 12v vs 5v per my previous post.

Typically you can use a wire to either tail light or the 3rd light. Or sometimes there are wires coming off a switch at the top of the brake pedal. If I remember correctly, 1999 Boxster had such a switch. I can look at wiring diagram in Bentley book later.

 

The other thing is you will want a single wire soldered to a binder connector for the Evo unit. Alternatively you could take an extension and cut it up, but that's hacky. We used to sell a kit for this when I did this for business, perhaps one of the AiM dealers could make one for ya.

 

Making the wire won't be a problem I think