The buck-boost takes a wide range of DC voltage inputs, from 5 to 32 volts, and puts out a voltage you choose from a range of 1.25 to 35 volts. You select the output voltage by turning the brass colored screw on the top of the tall, rectangular blue element on the module shown in the link I sent. The buck-boost should more correctly be called a controller because it converts/controls/adjusts input voltage to the output you want. When starting a train, the LEDs will illuminate just before 4 volts on the track. As the train picks up speed when you apply more voltage from the transformer or power supply, the illumination stays at the same brightness because the buck-boost module takes in whatever voltage you apply but only puts out the voltage to the LEDs that you selected when you adjusted the brass screw. (You need to check the output voltage before connecting the LEDs because I found that the output on the ones I bought was about 25 volts, too much for the LED strips. I adjusted the screws to reduce the voltage to 7-8 volts, and then trimmed each one to match the lighting of all of the finished cars.) The LEDs have the same brightness when the train is almost at a crawl or when going at top speed.
The buck-boost converter on the website is nearly identical to the ones I used and has the same specifications. In the web picture, the bottom corners are the silvery pads for input--negative on the left and positive on the lower right. Those pads easily take a spot of solder when a wire is passed through the hole and bent over the edge. The output pads are on the opposite side of the converter/controller.
Let me know if the diagram did not appear this time. I see it in my browser, but different browsers act differently.
Good luck and Merry Christmas,
Terry
