My first curcuit.

Forum 2005-2010 (read only) Hardware Interfacing
1

I need help designing my first circuit. I hope it's ok posting here.

I just got a new head unit put in my car with a dvd player, and unfortunately when I disengage the e-brake the video cuts out and my son can't watch from the backseat. I don't want to buy more lcds, and frankly my car is too small for more anyway.

I thought this would be easy, but alas, those clever folks at alpine have the stereo hooked up to both the e-brake and foot brake.

To engage the video I have to

  1. engage foot brake
  2. release e-brake
  3. engage e-brake
  4. release foot brake

I think I could easily do this with an arduino... if it weren't for the voltages. 12-14v. I want to make a circuit that I can hook these 2 wires into, press a button, have it alter the current on two leads corresponding to the above sequence.

So I'm hoping you wonderful people here could give me a hand. What do I do about the voltages, first I have to drop the voltage from 12-14 v to the 5-9 range right?

Then I need to set up two circuits that go high/low that I can tap from the head unit. I'm thinking I can just use some transistors to get the voltages correct. what kind of transistors do I use?

any suggestions would be appreciated

2

Caveat - I know nothing about car stereo/video, but i thought i'd take a shot at this. a few clarifying ?'s:

  1. Why would they connect the DVD player to the brake system?
  2. What is the underlying purpose of going through the sequence you outline?
  3. When the foot brake or the hand brake is activated, there is a sensor line that goes high (12-14V)?; and you want to have the Arduino connected to the head unit to simulate these sensors, correct?
  4. You're not planning to tie directly into the foot brake and e-brake sensor lines? (I'm not sure what other systems these feed...)

I can't imagine that this is going to be a high-current circuit, so it seems a simple NPN transistor (2N2222) would do to translate the signal levels 5V --> 12V. would this work: (untested...)