Tænding 4efe af Claus Hm, tror det skal være lidt mere detaljeret, et udklip fra manualen.
E.1 The Input Trigger
The E6A ECU has been designed to trigger from a square signal that varies from a ‘low’ of
zero volts (ground) to a voltage between 5 and 15 volts. The actual value of this ‘high’ voltage
is not important because it is the transition from ‘low’ to ‘high’, or ‘high’ to ‘low’, that is used
to trigger the E6A ECU. This transition is referred to as the Trigger Edge and will be shown
in the following illustrations as an upward or downward facing arrow. An upward facing arrow
would indicate that the trigger edge is the transition from low to high and this is called a Rising
Edge trigger. If the trigger edge occurs on the transition from high to low, it will be shown as a
downward facing arrow, and would be called a falling edge trigger. See Figure E.1.
Figure E.1
In order for the E6A to operate correctly a trigger edge must be generated for each spark. This
edge must occur a fixed number of degrees before top dead centre (BTDC) and must not
change. The position of the trigger is given in crankshaft degrees and is called Trigger Angle.
In addition there should not be any variation in the trigger angle between cylinders. The E6A
can be set by the user to have its trigger edge occur between 60° and 100° BTDC.
In the example shown in figure E.2a the trigger occurs on a rising edge at 70° BTDC. The
second transition, from high to low, could occur any time after the rising edge. In some
installations the second transition will coincide with 10° BTDC or TDC itself, or it could
happen as close as a few degrees after the trigger edge. This second edge will have no effect
on the correct operation of the E6A ECU. It is only the position of the triggering edge that is
of importance.
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Figure E.2
In the previous examples the trigger edge has been shown as the first edge of the trigger pulse.
The trigger does not necessarily have to be the first edge of the trigger pulse. Consider the
example shown in figure E.3. In some trigger devices the pulse given for cylinder one would be
a different width than the pulses given for all the other cylinders. If the first, in this case, rising
edges were used as the trigger edge then there would be a variation of 20° between the trigger
for cylinder one and all other cylinders. This would lead to cylinder one being 20° more
advanced than all the other cylinders and obviously this would be unacceptable. The answer in
this case would be to set the trigger point so that it is at a falling edge and to have the trigger
degrees set to 60° BTDC.
Figure E.3
E.2 Trigger Devices
The output of Hall Effect or Optical sensors could normally be connected directly to the input
trigger pin of the E6A ECU. Many distributors uses in original equipment manufacturer’s
computer controlled ignition systems would be fitted with Hall / Optical triggers. The internal
structure of such distributors is usually configured so that a chopper wheel attached to the
distributor shaft passes through a gap in the sensor. These devices require three connections :
Power (normally +12v)
Ground, and
Trigger signal output.
Assuming that the timing edges conform to the details set out above, a distributor such as this
would connect directly into the E6A ECU. Often these distributors have a rising edge trigger
at 70° BTDC.
