Voltage of blue wire

Discussion in 'Electrical' started by dougsr.874, Jul 23, 2014.

1. dougsr.874Active Member

So the white wire outputs about 6 volts...how much does the blue wire output?????.....what would happen if the blue & white were wired together????

you'll fry your coil...

while you CANNOT measure the voltage between blue and black with an ordinary multimeter, they should be around 400 volts. you will usually read 40-70 volts.

you need a special multimeter that can measure the voltage despite its varying frequency. a standard multimeter measures in RMS, and also requires 50/60hz, which is the frequency of most standard AC outlets (that means your household power). an aeroplane, say, has an AC power supply of 400hz. a regular multimeter will give a false reading at this frequency.

6 volts wont make any difference in voltage, but the difference in the way the coils are wound WILL. that 6v is also load dependent. as load increases, so does current. but then the voltage drops. it is COMPLEX! if you dont understand what ohms law is.... GOOGLE!

basically... wiring that white wire up to anything makes for a good killswitch, until the magneto fries itself. which is a topic i am not about to try and explain!

do some research into electromagnetism, inductance and various other aspects of electricity, especially AC electricity, because it really is NOT a simple answer.

3. jaguarWell-Known Member

with an analog voltmeter set on AC volts , with the blue wire disconnected, you should read at least 30 volts while pushing the bike.
the white wire is for powering LED headlight/taillight, not for use with kill switch

4. FabianWell-Known Member

So Jaguar, how did you work out the correct AC voltage for the ignition side of the magneto coil (blue wire) and what input voltage does the CDI normally operate at?

5. jaguarWell-Known Member

that's from my experience testing my own with a cheap voltmeter. Results vary with different voltmeters.
the higher the rpm the higher the peak voltage coming from the stator coil. Peak voltage may be around 200 volts at high rpm.

6. FabianWell-Known Member

What max voltage is the Jaguar CDI set to accept?
What is the minimum input voltage that the Jaguar CDI will operate?

i know im not the questionee here, but when i was making these things, i could get a spark from the 15 volt winding of a regular AC transformer. ie, 15volts, RMS. at 50Hz. it also burnt out resistors, im guessing because of too much current flow. fine on the engine, even 1/4 watt ones, but 5w ones would start smoking and turn brown on standard 50Hz AC!

the stock cdi couldnt do a thing until i got to 30+ volts.

no difference in output sparks either, once sparking.

remember that the output of the HT also is NOT a sine wave.

the multimeter test is just that, a test. not a definitive result. it shows the things work!

whats needed for true readings of output voltage, which also varies depending on load, is a silly scope.

(oscilloscope if you arent familiar with the most necessary tool of electronics)

this way, you not only get an idea of the shape of the waveform, you can get an average voltage output. remember, its a slope. the peak voltage is not the same as the "average" voltage, which is what RMS means. root mean square, or about 0.707 of the actual peak voltages.

just about every CDI unit, be it the self powered ones on HT's or pitbikes or dirtbikes, use roughly 400V RMS. RMS doesnt work if the waveform isnt a sine wave. so you may get a peak voltage of 600-700 volts. while a RMS meter will only read 100 volts or so.

battery powered CDI units have an inverter circuit, converting DC 12v (or whatever the power supply is) into, you guessed it! approximately 400 volts.
further complicating the issue are the diodes, which always drop 0.7 volts, and any resistance in the circuit, and the "chargeability"(ooooh, no spell check so it must be a real word!) of the capacitors. a capacitor NEVER fully charges, nor will it completely DISCHARGE, even when short circuited.

well, not very quickly, at least... especially if theres any resistance. the basics of the CR timing circuit. and every conductor has resistance. excepting superconductors. which are another kettle of fish. ohms law breaks down completely as soon as theres a 0 in the equation... 1000000 volts = infinite current x zero resistance. substitue one millionvolts for any voltage....you still get infinite current. think about it you cannot multiply or divide by zero! super conductors dont actually conduct electricity. more like standing waves of energy. induced currents, that never fade away, unlike the LC tank circuits used in a radio, for instance.

fiendishly complex, electricity. its like juggling eels! one part affects another part and you gotta keep your eyes on everything at the same time... oh, the basics are simple enough, but it can get rather confusing if youre not careful.

Fabian likes this.
8. FabianWell-Known Member

HeadSmess, you really know how to take electrical fundamentals and sex them up.

I always enjoy reading your explanation/s :2thumbsup:

and i dont really get into it, just fiddle occasionally, get frustrated, smash things, leave em to stew for a few years... i always seem to make amplifiers that oscillate or oscillators that simply dont :icon_cry:

oooh, look! theres your first post!

and i quickly scanned through to the end, seeing if it was answered...

my first thought was the final answer it seems. you got lucky? and had a 180 degree out of phase magnet the other option was the magneto being wound the wrong way. but that wasnt it, you swapped it.

be interesting if you still have it kicking around, and held a compass near it... then compared it to a good one. or held them side by side. you shouldnt be able to hold two good magnets together, with the keys in line, as like poles repel... now i have to dig through my box and confirm this...

no idea how they managed to get it backwards! im sure they slot enough of these things to have some type of magnetically polarised jig on the machine...

on that note, i was looking at a few magnets some time ago, and ive found over 15 degrees of difference between the location of the keys! also some noticeable differences in strength. both will affect the timing. as will the number of windings on the coil. the problem with swapping parts. grr! i may be anal, but theres a reason i stick to one tried and trusted size/supplier now.

ah, its interesting looking back on memories names that have vanished.... oh my... 5 years ago. how time flies