A Capacitor Discharge Circuit
for Lionel O27 Switches

      Here is a handy way to use a traditional model railroading technique with the inexpensive O27 switches. First you need to modify the switch for use with a separate power supply/transformer. (Lionel has a video on YouTube showing the procedure: O27 Switch for Fixed Power. However, with some switches, the little wire to the solenoids is covered with a braided cloth insulation without much excess length to "tease" from the compartment, and it is a tedious effort, but worth it. Remember, these wires have a thin clear varnish coating that needs to be scraped off before soldering.) But with this circuit, the switch is still track fed with no other power supply or transformer used. There isn't any buzzing and it takes about 3-5 seconds for the cap to recharge, so the solenoids aren't constantly firing as a train passes through the switch. Just be sure to put the capacitor discharge circuit in a project box for safety, and be sure to maintain the correct electrolytic capacitor polarity.

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