Driver for the turnout coils defined

For the turnout coils, I have decided I would have to check what current was necessary for it to switch. I tried to do some test with the multimeter, but due to the high current spike during the commutation and the narrow switching interval, it was not possible. No problem at all, I attacked the issue with an oscilloscope. The results and its schematics follow:




The first one is related to a no switching event, the second, to a switch.

After many days of research, asking for help to Alexis and Samuel, and hours navigation in Farnell and Radiospares, the best solution I have found was to use plain NMOS transistors with Schottky diodes. The ICs for driving relays are very expensive, don’t support enough current and come with functions our project will never use.


Work during the weekend

Hello everyone,

So my task this weekend was to conceive how we could control the railroad switches with our micro-controller. So I removed a switch from our scale model and disassembled the system used to commutate the switch. Unfortunately, the datasheet from the turnout mechanism was only designed for operation with DCC decoders. Finally, I came across a DIY website which had controlled the same mechanism. They did not give much details about their board, but at least explained how to drive the device. So I picked up a DC Power Supply and tried to replicate the results. Yeah, it worked.

After a long research about how to drive coils with transistors, I realized the following schematics:

I will still simulate the voltage spike when the transistor switches on, to decide weather or not place a Zener diode in parallel with the coil.