ARDUINO’s can control many things – what do you want to control?
Arduino’s are small circuit boards with various input/output terminals, power input, USB connector and a few other components that allow users to program and implement the microprocessor on the board. Keep in mind that though the USB cable plugs into a standard USB port, the connector that plugs into the Arduino is much larger than that which connects to a cell phone and of a different physical shape. So, don’t misplace the cord that is supplied with the Arduino (at least by AllElectronics).
Arduino’s come in various sizes and configurations and can be “accessorized” by adding “shields”. Shields are add-on boards attached to the basic Arduino for specialized functions such as wi-fi, internet connection, voice box (think Stephen Hawking), joystick control, etc. You can even use a shield to turn you Arduino into a “cell phone”.
The following are two commonly available Arduino’s:
The Arduino UNO is a small micro-controller board using the Microchip ATmega328P microcontroller with 14 digital input/output pins, 6 analog inputs, a USB connection and a power input plug that can be used if not plugged into a USB connection. The Arduino “Uno” is about 2″ x 3″ and stands about 1/2 high.
The Arduino Mega is a larger board based on the ATmega2560 and comes with 54 digital input/output pins, 16 analog inputs, 4 UARTs (hardware serial ports), and similar hookup connections. The Arduino “Mega” is about 2″ x 4″ and also stands about 1/2 high.
You can download free Arduino software to develop the program (called a “Sketch”) that will run each Arduino or you can edit sketches online and save them to the cloud. This link leads to a page where you can do either:
https://www.arduino.cc/en/Main/Software
For a model railroad, you may want to control crossing gates & associated bells and lights, block signalling, track occupancy detection, building lighting, Servos for animation and turnout control, etc.
You can find sketches already written for most common usages in the online library. The sketch determines the usage (input or output & the type) of each pin. For example, if you wanted the Arduino to control a crossing gate you could embed photo-resistors under the track before and after the crossing and assign them to a pin(s) you designate “input”. You would define another pin as output that would output either 3.5v or 5v or 5 volts. This could start a light flashing and another pin could power a servo to control a crossing gate. At the same time the Arduino could be randomly controlling other pins, connected to LED’s, turning them on and off to make a building look occupied with folks moving from room-to-room.
The uses for these devices is endless. The amount of power that it can put out is not. If you are running a heavy drain you would need to use a transistor or a relay to control a larger amount of power. Remember, the power is coming from the same low-powered USB-type source that charges a cell phone.
I obtained my original Arduino Uno from Amazon as part of a $70 kit
https://www.amazon.com/gp/product/B009UKZV0A/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1
that included a breadboard, various electronic components, a large number of connector leads, and a project book. All Electronics sells the Uno for $14
(https://www.allelectronics.com/index.php?page=seek&id%5Bm%5D=pattern&id%5Bq%5D=ard-21
and the Arduino Mega for $28.50
https://www.allelectronics.com/index.php?page=seek&id%5Bm%5D=pattern&id%5Bq%5D=arduino+mega
There is a lot of information available, so I won’t go into greater detail. Instead, here is a link to the Wikipedia page on Arduinos:
https://en.wikipedia.org/wiki/Arduino
and here is a book that I have found to be clear, concise, and filled with many good ideas:
Exploring Arduino by Jeremy Blum published by John Wiley & Sons, Inc.
Model Train Operations 