Electrodroid is an Android app designed for electronics hobbyists, but it has uses for model railroaders too. Its LED calculator is invaluable when using LEDs to light buildings, cars, locomotive cabs or headlights, or for other projects. Knowing the input voltage, you can then determine what resistors to use to protect the LED.
The voltage drop calculator is useful too, if less obvious.
Here’s a common problem: On distant parts of the layout, the train slows down for no obvious reason. That reason is voltage drop over the track as the train gets further from the transformer. The solution is to run more feeder wires. But what size wire do you need?
Enter the length and gauge of the wire into Electrodroid, and it will tell you how much the voltage will drop across the run. Use a heavy enough wire that you don’t get an appreciable drop, since some additional drop is inevitable once the current reaches the track.
This allows you to determine if the wire you have on hand is adequate for the project, or if you have to buy wire, it tells you the size to buy without overkill.
Sometimes you need a specific voltage in a project, but that voltage is something other than your transformer output, the 5 volts that a 7805 can deliver, or the 12 volts that a 7812 can deliver. Using the adjustable voltage regulator tool, you can quickly determine what resistors to use in conjunction with an LM317 regulator, or you can use the voltage divider tool to quickly determine what resistors to use if you want to do the job with resistors alone.
If you have a parts drawer full of random resistors from old projects, Electrodroid’s resistor color code tool will help you identify them. And the resources tab has the codes for capacitors so it can help you identify those too. Now if there were only a way to get the computer to sort the contents of that drawer for you…
And speaking of the resources tab, it also contains a list of the symbols used in schematics, which is helpful for beginners and as a refresher.
The more skilled you are with electronics, the more you’ll find yourself using this tool because it has calculators and pinouts for dozens of electronics applications. I don’t have one to check against anymore, but the free version appears to be enough to replace the old electronics pocket reference books that serious tinkerers carried with them in the 1990s.
But even if you never do much beyond sizing wires and calculating LED circuits, Electrodroid is invaluable and will help you build a better railroad.