Powerdynamo brings new ignition & light
to your vintage motorcycle
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Powerdynamo brings new ignition & light |
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What is the relay in many Powerdynamo Systems for? Do i need it? |
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| Starting to say that he who fits the relay but has no battery in the system will probably never get spark. Same for those who use a standard vehicle relay without pin 87a. | |
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 We talk of this little fellow here. |
And please note that though this is a vehicle relay, it is still special
as it has a closed-circuit pin 87a (the one in the middle), most
standard relays do not have). 
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| To explain the purpose of the part, a little excursion into ignition: | |
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A battery based system is switched on by bringing voltage to the
ignition coil and switched off by taking that voltage off again. |
A magneto based system is switched off by short-circuiting the
voltage the magneto brings to the ignition coil and switched on by eliminating this shortcircuit.
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Most Powerdynamo ignition Systems are magneto based. They need the arrangement as explained above for
magnetos. As long as the stock system had been magneto this is fine, the
main switch will function as it did before. If you had a battery based system however that your switch will not normally sport a facility for magneto switch off (some BMW singles have both, but this is an exception). In order to be able to use the stock switch and the original switch ON/OFF method the relay comes to work, inverting the switch function from the Run with closed to Run with open connection. |
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Pins 86 and 87a are to ground. Applying voltage to pin 85 will make the
relay contact switch the status of pin 30 from position 87a to 87. That is
from ground contact to nothing. With Pin 30 open, the system can run. Taking voltage off pin 85 (by switching main switch off) makes the relay snap back and close pin 87a (ground) against pin 30 which via the blue wire is connected to the CDI, short-circuiting it. A typical Powerdynamo wiring diagram with relay would look something like this here |
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The whole thing surely only works with a battery present. How else could
you activate the relay to give way to ignition? If you drive without
battery you will have to skip the relay and connect the blue wire to some
manual switch. Say a push button one at the handlebar. Alternatively misuse the headlight flasher knob to do the job or any other switch. You might use e.g. the terminal provided on many old main switches for pushstart Please note, the blue wire will carry some 300 volts (at very low amperage) which, even if not dangerous is quite painful. A typical Powerdynamo wiring diagram would look something like this here |
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