Our previous Programmable Ignition was originally published in
March 1996 and proved to be a very popular project with readers. This was
subsequently updated as the Programmable Ignition Timing (PIT) Module in the
June and July 1999 issues of SILICON CHIP.
The updated PIT module included a basic 2-step advance curve
and a 1-step vacuum advance that changed the timing according to engine load. In
operation, it was used to control the High Energy Ignition design from the June
This latest Programmable Ignition from SILICON
CHIP is far more advanced in features and its ability to produce an accurate
advance curve. It is also a complete stand-alone ignition system that is
triggered by an engine position sensor and then drives the ignition coil. It can
be triggered from one of many sensors in a distributor, including points,
reluctor, Hall effect, optical trigger and the 5V signal from the car’s Engine
Control Unit (ECU).
In order to measure engine load, the Programmable Ignition can
use a Sensym absolute pressure sensor. In fact, provision has been made to mount
this sensor directly on the PC board, the sensor then being connected to the
engine manifold via plastic tubing.
Alternatively, you can connect the ignition circuit to an
existing manifold pressure sensor if present. This is commonly called a Manifold
Absolute Pressure (or MAP) sensor and is found on many cars these days. You
could also use a secondhand MAP sensor from an auto wrecker.