[VAC] Re: Tekonsha Brake Controllers

["Dr. Gerald N. Johnson, electrical engineer" <geraldj@xxxxxxxx>]

The Kelsey-Hayes controller I'm using has a plug in remote push button
with just two connections. It wouldn't be hard to determine the
characteristics of that button (I bought but don't use since I mounted
the controller in a very convenient position) and build a bit of
electronics to convert from a sensor to that controller input. Far
easier than working out the internal controller circuit.

We can't tap the hydraulics "in front" of the pulsing stuff, there is no
front or back in a hydraulic pipe, it all gets the same pressure, that's
what generally makes hydraulics so handy.

As for getting the auto makers to create a super brake controller, that
could be difficult (Not Invented Here syndrome), but since the antilock
brake system is closer to being integrated into the main computer, it
would just take some additional software and one two output connections
to add trailer brake controlling to the computer. There'd need to be a
pulse width modulated output for the brake wire and an output to turn on
the brake light, or to sense the brake light. Externally there'd need to
be a (probably optional) power control module with controlled maximum
(to prevent locking the brakes, the current limiting being the analog of
the wire resistor on the old hydraulic over electric brake controller).

It sure would add complication to the trailer but an antilock controller
for the trailer brakes could simplify the modern pendulum control. Each
wheel would need an individual control circuit and an individual
rotation sensor much like the one that's in the differential on my Ford
truck.

Sensing pedal pressure shouldn't be too difficult. There probably are a
dozen techniques that would work. Mostly based on a stiff spring of some
sort with some electrical measure of how far the spring has been
compressed, could be optical, could be piezoelectric, could be a linear
or rotary potentiometer, COULD BE THE KELSEY-HAYES remote button with a
stronger spring. Most of these types of sensors are used in the vehicle
for engine control, like sensing throttle plate position for the
computer, or intake vacuum, or dialing the digital radio... A
piezoelectric plastic membrane that could fit under the rubber brake
pedal would be fascinating, though take more electronics probably than
some others. Adding .040" of membrane sure would be unobtrusive to all
drivers!

Gerald J.