Well, I tried that Hopkins brake controller over the weekend.. it was OK, I did feel safer with it than with time based controllers, but it has one terrible drawback.. it doesn't hold the brakes while you're stopped.. so if you're in steep country with heavy loads, all that is going to be on your truck brakes... It has an accelerometer and that's what it uses to sense how hard you're braking, the other problem with it is your truck brakes have to be able to get you into a decelerating state before the trailer brakes will kick in, and with heavy loads and steep hills that may be hard to accomplish.
The solution is only the Arduino with a brake pressure sensor on it, and a darlington transistor driver for the trailer brakes.. This is how the "Maxbrake" controller worked, and is no longer available, and cost about $700.. The new model trucks that have sophisticated ABS systems have integrated pressure sensors that actuate the factory brake controllers.. and I wouldn't be surprised if they ran over the CAN bus as well.
I think
PX2EG1XX750PSAAX Honeywell | Mouser
(http://ca.mouser.com/ProductDetail/Honeywell/PX2EG1XX750PSAAX/?qs=%2fha2pyFadugZgqe4NmGb03kkHg226aRZIB4OuOcIEtHn1wrfJ%2fOxd%2fYrn1bRqdoj) would be a good sensor for the application, Not cheap, but on a brake system isn't the place to skimp either
Is there any kind of ABS integration ?
Ideally a TPS type sensor for your brake pedal would be a simpler way to go ?
I've heard of them, and it certainly is a cheaper way, but from what I've heard it doesn't perform as well.. maybe something to do with the non linearity of the booster, etc?
What I was thinking along the lines was mounting an actual 5v TPS to your brake push rod. With a rigid mounted something, to pivot the TPS as you pressed the pedal.
You don't need 100% pedal articulation but you would need to remove as much dead pedal so you can measure that part.
Then you can map your usable voltage range.
well, it's the same input to the arduino, so it's only a matter of choosing which sensor you want to use.. input remains the same, though with the TPS version you may want to tie into the brake switch as well to be certain you don't apply trailer brakes while driving
Latch circuit on brake wire ?
yeah, something like that should work