Wiring SPDT On-Off-On with Relays

[Bdowdy07]

This is probably a very simple task but I cannot seem to figure it out. I built a radio cooler that has a SPDT On-Off-On switch and would like to achieve the following.

Switch position one - Radio only

Switch position two - Radio, Usb charger and led lights

Switch off - No current draw

What would be the best relays and configuration to achieve this?

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[keep_hope_alive Premium Member]

You can wire the Radio through one switch leg and the Radio, USB, and LED through the other switch leg.  A On-Off-On switch has a center common for the hot conductor.  Then you'll have the Radio power to both positions one and two.  USB and LED will only be wired to position two. 

You could also use relays.  You can dedicate one relay to Radio with a second relay powering Radio, USB, and LED.  In that configuration the On-Off-On switch would power the relay coils.  This allows you to use a smaller toggle switch since it won't see the current of the load.