janneman
Seaman Apprentice
- Joined
- Jun 26, 2007
- Messages
- 32
After digging a little on this forum, i thought it might be good to do a little more general topic on the working of the electrical side of this series of outboards.
Some topic parts mix in here; the ignition (stator, switchbox, bobine) and the instruments themselves (tach-meter).
In general, what i understand from the CDI in the thunderbolt series of outboards is that they work on basis of a constant DC voltage. Then the stator (fixed part of ignition and rotary thing on top) gives pulses / contacts as means of timing for when to spark.
At these pulses, the CDI discharges a capacitor (it's an abbreviation for Capacitor Discharge Ignition) to make a burst of current to the ignition coil (also "bobine") that transforms this into a high voltage peak (> 5000Volt
)
Out of the CDI/switchbox also comes a "kill wire". If this is shortened, the CDI gives no pulses so a running engine stops. (comes in handy sometimes )
Apart from the signals for the CDI box, the stator has coils that generate AC current. This AC is converted to DC by the rectifier, but then this electric signal still has a large portion of AC on it as well. One of the wires of that side of the rectifier is ment to hook up a tacho-meter.
Now here comes some lack of knowledge from my side.... Appeartly from what i've been reading here, there is a DC offset on it. But a tacho does not "see" the DC, it only reacts on AC pulses/waves.
What pulses do come out? Is there one pulse per ignition stroke? (that would mean in my case of a 4 cylinder 2-stroke that every revolution of the engine it produces 4 pulses. Hence (example) 3000 rpm = 50 rotations per second * 4 = 200 pulses per second (=200 Hz signal).
Some digital voltmeters can also measure a frequency, alas mine does not. Neither do i own an oscilloscope (for electronic noobs; instrument that analyses electronic signals).
anybody throw some more generic knowledge in here?
Some topic parts mix in here; the ignition (stator, switchbox, bobine) and the instruments themselves (tach-meter).
In general, what i understand from the CDI in the thunderbolt series of outboards is that they work on basis of a constant DC voltage. Then the stator (fixed part of ignition and rotary thing on top) gives pulses / contacts as means of timing for when to spark.
At these pulses, the CDI discharges a capacitor (it's an abbreviation for Capacitor Discharge Ignition) to make a burst of current to the ignition coil (also "bobine") that transforms this into a high voltage peak (> 5000Volt
)Out of the CDI/switchbox also comes a "kill wire". If this is shortened, the CDI gives no pulses so a running engine stops. (comes in handy sometimes
) Apart from the signals for the CDI box, the stator has coils that generate AC current. This AC is converted to DC by the rectifier, but then this electric signal still has a large portion of AC on it as well. One of the wires of that side of the rectifier is ment to hook up a tacho-meter.
Now here comes some lack of knowledge from my side.... Appeartly from what i've been reading here, there is a DC offset on it. But a tacho does not "see" the DC, it only reacts on AC pulses/waves.
What pulses do come out? Is there one pulse per ignition stroke? (that would mean in my case of a 4 cylinder 2-stroke that every revolution of the engine it produces 4 pulses. Hence (example) 3000 rpm = 50 rotations per second * 4 = 200 pulses per second (=200 Hz signal).
Some digital voltmeters can also measure a frequency, alas mine does not. Neither do i own an oscilloscope (for electronic noobs; instrument that analyses electronic signals).
anybody throw some more generic knowledge in here?
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