Electronic car ignition
author: EDY Cornholio
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ATTENTION: Don't construct this project
until this label is removed. There are some
corrections that must be done in order to be full
working. Sorry for the inconvenience.
This scheme is for 4 cylinder motor. This
will make your car spent less fuel, be a little bit faster
and you won’t have to frequently open your distributor cap
to change the contact buttons thus wasting less money.
T1/T2 create one monostable multivibrator in which C2 and
R5 determine the length of impulse which is 1,5 msec. Next
in line are T3 and then T4 which is Darlington transistor
specially developed for electronic ignition which is used
as a switch to turn on/off primary coil. Impulses from
switch P turn on monostable multivibrator T1/T2. You need
to un-connect capacitor that is in distributor cap because
it is not needed anymore. While switch P is closed T1 is in
off state but T2 is in on state, also T3 and T4 which
enables current to flow trough primary coil. When switch P
is opened, T1 gets in on state for a moment causing C2 to
charge over R6 which makes T2 go to off state because of
voltage drop on R6. When T2 is off also T3 and T4 are off
and current that was flowing trough primary coil is
stopped. Because T2 is in off state, voltage on R8 is
increased which is passed trough R5 on T1 base which is
still in on state and C2 is still charging. After 1,5 msec.
C2 value reaches the level where T2 goes to on state again
and T1 goes to off state. Now T2, T3 and T4 are in on
state, again, and current flows trough primary coil again.
R2 and D1 are used to neutralize the effect of impulses
caused from «jumping» of switch P which could turn on
monostable multivibrator when it shouldn't.
Zener diodes Z5 and Z6 are together with R10 limit
overcharged voltage impulses that are caused by self
induction of primary coil which could damage T4. They
should be connected as close as possible to T4.
D7 protects device from wrong polarity.
Coil should have ratio of 1:80 or 1:100 with external
resistor Rv which is used for better cooling. Total
resisting value (Rp) of primary coil and Rv resistor
shouldn't be under 1,6 ohm's so current trough T4 wouldn’t
be bigger than 10A.
Depending on Rp, R9 have different values:
120Ù/2W for Rp tot > 2,2Ù
100Ù/2W for 1,8Ù < Rp tot < 2,2Ù
82Ù/3W for 1,5Ù < Rp tot <1,8Ù
T4 has to be heatsinked!!!
All resistors are 1/2W +/-5%
D1-D4 = 1N4148
D5-D6 = BZX85C – 180 (replicable with all equivalent types
with power of 1,3W)
D7 = 1N4001
R1 = 470 - 1W
R2 = 22k
R3 = 2,2k
R4 = 1k
R5 = 4,7k
R6 = 39k
R7 – R10 = 100
R8 = 680
C1 – C2 = 47nF (ceramic)
C3 = 0,22uF 400V (ceramic)
C4 = 100uF (electrolytic)
T1 – T2 = BC327 (BC327-25, BC327-40)
T3 = BC237B (BC547B, BC547C)
T4 = BUX37 (BU323, BU920, BU921, BU922, BUV37B (u TOP3),
BUW29, BUW81, MJ10012, MJ10013, MJ10014, TIP662, TIP665,
Download this project in .doc