Analog CDI v2.0
Synoptic.
Schematic.
| Analog v2.0 | Schematic | Parts list | Wiring |
| Analog CDI for XT600 | Schematic.pdf |
liste.txt | wiring.gif |
Circuit board.
| Analog v2.0 | Circuit board | Components |
| Analog CDI for XT600 | Cuivre.pdf |
Composants.pdf |
Working.
This assembly replace the genuine CDI.
The alternator winding produces a alternative voltage
between the red and brown wires.
There is 6 pulses by rotation
between ±50v at low RPM until ±200v at high RPM.
This tension is rectify by the bridge B1, and loads C1 to a average voltage of 270Vcc.
Both pickups supplies alternative impulses from ±10v (at idle)
until ±20v (at high speed)
One pickup with 12° advance on the white/green wire, the other with 36°
advance on the white/red wire
(The green wire is the common of the both
sensors)
At startup and iddle, the positive pulses coming from
the 12° pickup goes through diode D1 then trigger the
thyristor T1, (a TYN1012
12A 1000V, or a BT151-800).
T1 discharge the energy stored in the capacitor C1
into the
primary of the ignition coil, which
delivers high voltage to the spark plug (until 20kV)
At higher RPM, the 36° pickup provide the pulses through diode D2
Ajustable resistor R3 is used to adjust the time when the pulses coming from 36° pickup, will trigger the thyristor.
The threshold is adjustable from 2000 to 5000rpm
Start tuning with R3 at the maximum (totally screw) then
slowly lower the resistance.
| This ignition need either 2 pickups: |
or only one pickup |
1st
pickup at 36° BTDC: and 2nd pickup at 12° BTDC:  |
Positive than negative: |
But not negative than positive! |
Nota.
With this short, we get this equivalent circuit:
D2 allows the positive wave to pass.
D3 kills the negative peaks of tension
produced when the thyristor cut off
Tested good on:
- Yamaha YZ125 (1987)
- Yamaha XT125 (1982)
- Yamaha XT400 (5y6)
- Yamaha XT550
- Yamaha DTMX125
- Aprilia Climber 280R (1994)
Pictures.
Version 1.0.
Version 2.0.
Caveats
Never
run the engine if the exit of the ignition is disconnected from the
coil or if the ground is not connected (PAD1
or PAD2 unconnected) otherwise the
tension rises over 1000volts and destroy the SCR.
Never
run the engine without any spark plug.
Due to the high secondary voltage, it is possible to damage the
internal insulation of the secondary coil.
This simple unit is
design for XT, which have 2 pulsers: one
for idle, one for middle/high rpm
The KLR and others bikes whith only one pulser, have just one for
middle/high rpm and there are some electronics inside their black box
to delay the pulse at idle.
With this unit, the spark will appear too soon.
Therefore you'll have kick back when kick start and (if it's starts!),
the engine will bang a lot at idle (this can damage the connecting rod)
I disclaim all responsibility !!
If it's ok, well done! you made a success of your first electronic ignition. You can use it as a spare unit.
The pulse from second sensor (sensor A and magnet A on the left drawing) is early 12 ° before the TDC.
(Reminder: the TDC is finds when the sign like a H engraved on the rotor is view by the small opening on the left crankcase.) The advance is sufficient to start the motor straight.