where to insert the switch for dynamo light

Hey there,
I'm looking to add a switch to my next dynamo light to shunt 3 of 4 LEDs for riding down a well lit path where I don't want to blind oncoming pedestrians and other cyclists.
For my current light the switch is on the AC input. For my next one I was planning on using a 3 position switch with center off, to switch between LEDs and still have an off postition. With this setup I would need to place the switch after the rectified AC.

So my question is, with the switch in the off position, would the AC input current still flow through the rectifier and back to the source even though there would be no load on the rectifier output? would this current flow increase hub drag?

Thanks,
Dan

As long as you are disconnecting the LEDs, there shouldn't be any current flowing.
You can demonstrate this for yourself by putting the bike in the workstand (or just hold the dynamo wheel off the ground). Disconnect the dynamo, spin the wheel, and see how long the wheel spins. Now take a paperclip or something and short out the dynamo and spin the wheel again (it should stop much sooner than when the dynamo is disconnected).

Hook up your light system and spin the wheel again. With the switch in the "off" position, it should spin just as long as when the dynamo was disconnected. If it doesn't, there's something wrong with how the switch was wired.

There may be a concern about the voltage rating of the rectifier diodes in this scenario... If the diodes aren't rated for 100v or so, then the dynamo might damage them. (this depends on how much open circuit voltage the dynamo will create, which depends on the dynamo and how fast it is spinning) I've gotten over 100v out of a Schmidt hub dynamo at a speed of 50mph. Your Voltage May Vary.