Short circuit protection with globes and PTC fuses

For short circuit protection on the GC&SF I use devices assembled using car lamps and PTC fuses. Details of how they work, and how to build them can be found at:

For more technical details, I highly recommend that you refer to Marcus Amman's page at:

It is very important to note that these devices DO NOT act as circuit breakers. According to the RR-Cirkits website, they drop the current "to a safe value until the short is completely removed". Furthermore, they will probably prevent your DCC system's own circuit breaker from activating.

Before installing these devices I was a regular operator on several larger layouts that relied on only the DCC system's circuit breaker for short-circuit protection. On those layouts it seemed that every few minutes the whole layout would shut down because somebody had run against a turnout that was thrown against them.

When I converted my layout to DCC I resolved to provide each town and staging yard with its own short circuit protection, so that when an operator ran into a turnout that was thrown against him, only he was affected. I installed 9 devices protecting my 7 towns and 2 staging yards and they've worked very well for me. To do that with electronic devices such as DCC Specialties PSX-4 units (I would need 3) would have cost me around USD $400. Instead, I've spent less than $25.

Having said that, I did have to replace a melted truck early in 2017 when an operator derailed his loco in my hidden staging yard, and didn't alert me to the problem until the damage had been done. The replacement truck cost me about $20, so I have no regrets about not installing PSX-4s across the entire layout. However, I have since removed the car lamp device for that hidden area, and it now relies on the DCS circuit breaker for protection. Short circuits in the hidden track area now shut down the entire layout, but that's okay with me as such problems usually block the ladder, throat or approach tracks anyway, and I don't want more trains entering the area before the problem is cleared.


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