My three year old grandson loves his LEGO train, and this Christmas he asked if I could make him a few remote switches (OK, he had a little prompting from me on this). I knew there were other solutions out there, but I wanted to spin my own. I'm a radio control model airplane enthusiast, so my solution involved components from that hobby. Total outlay for the components for four train track switches was $55 on Amazon. That got me four servos, a servo tester, and a battery box for four AA cells to power everything. All other parts are official LEGO, and the switches required no modifications.
The pic shows a left turn switch modified to be a remote switch. The servo is a little hard to see, so I put an extra servo in the pic in the same orientation as the one in the mod. The device with the red knobs is a servo tester that can drive up to six servos. It's mounted with double stick tape on top of the battery box. Each servo is wired to the tester, and I later lengthened the cables to 7' myself. The servos are exactly 40 mm long, perfect for 4+1=5 nubs of LEGO spacing--the servos just press-fitted in. I cut a piece of LEGO base panel to engage with the control arm base of the switch. Just a simple LEGO build from there on!!!
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