27-12-12, 02:36 PM
Relays can be used for various purposes: in this case it's providing a shorter, lower resistance path for the current to get to your accessories. It also has the benefit that it reduces the current that the ignition switch (and anything else in the switched live supply) has to handle.
I think the additional "relay" in your drawing is just a switch so you can turn off the driving lights independently, though it could be a relay if you want to keep the high-current path as short as possible or could be omitted altogether if you don't mind the driving lights being on all the time your switched live is on.
Relays can also be used to provide logic functions. For example, the original Fazer headlights had a left side dipped beam that was on all the time (if the lights were switched on) and a right side H4 bulb that only made use of the main filament. Since the circuit diagram in my manual omitted the fact that there was a switching dipped supply available in the connector box under the tank, I derived my own using a relay and the existing headlight feeds so the dipped filament in the right hand lamp came on when dip was selected and went off when main beam was needed.
I think the additional "relay" in your drawing is just a switch so you can turn off the driving lights independently, though it could be a relay if you want to keep the high-current path as short as possible or could be omitted altogether if you don't mind the driving lights being on all the time your switched live is on.
Relays can also be used to provide logic functions. For example, the original Fazer headlights had a left side dipped beam that was on all the time (if the lights were switched on) and a right side H4 bulb that only made use of the main filament. Since the circuit diagram in my manual omitted the fact that there was a switching dipped supply available in the connector box under the tank, I derived my own using a relay and the existing headlight feeds so the dipped filament in the right hand lamp came on when dip was selected and went off when main beam was needed.