Controlling servos with Arduino

Drive visible part of the lay-out

All turn-outs, semaphore signals and train crossings are driven by a servo in the visible section. After experience with brand-specific magnetic articles, universal turn-out drives and memory wire, I find the servo drive to be the best choice due to a number of important advantages.

1. Can be mounted in any conceivable location, even several decimeters away from the moving mechanism. Both on and under the table.
2. Very reliable.
3. Easy installation with millimeter-precise adjustment afterwards.
4. Cost per servo is not so high. They are available for purchase locally or online. However, it is important to search for reviews online. I have had bad experiences with the cheapest options. Some common problems are spontaneous movement due to interference from running trains. I have had to replace many of these servos. I have had very good results with racestar and AZ-delivery,
5. Connection using three wires instead of four. (2 x power supply + 1x signal)
6. Almost silent operation.
7. Slow conversion (adjustable).

Hardware:

The servos are controlled by a printed arduino uno r3 circuit board. The photo shows a test setup. It is convenient to always have this at hand. Purchase extra boards for mounting under the table. Required for this test setup is an Arduino Uno R3 itself, a protoshield for an additional piece of electronics, a breadboard, jump wires, some electronic components and a servo. In case of a continuous point switch, a relay or switch is required for polarity reversal. On the right side of the Arduino board in the photo, the "prototype shield" is visible. Recently purchased for a few euros, it allows easy addition of electronic components without soldering using the included mini breadboard. Later, the board can be used without the mini breadboard to permanently solder the components, as shown further on this page.

Soldering components:

The photo shows how to solder the components if you want to get rid of the test breadboard. An additional three-pin plug-in connector has been added. The two outer pins are the digital rail voltage (DCCIN). The middle pin is the common GND if the servos are connected to a separate power supply. From this board, only the pins on the bottom left of the board remain to send the signal to the servo or polarity relay. When powering the whole system, make sure that it is sufficiently dimensioned. In my case, I have provided each Arduino with a 9-volt power supply and provided the servos and relay board per Arduino with a 5-volt power supply.

Software:

First, the software for the arduino needs to be installed on your PC. If you are using a clone of the original arduino, you also need to install a special USB driver. Without this, it will not work. On the internet, you can find all kinds of ready-made sketches (programs for the arduino). These can be read into the arduino using the "Upload" function. Once uploaded, the arduino can do its work independently of the PC. A good starting point for getting to know the arduino better is the website arduino-lessons van Simon Monk. The first lesson explains a small sketch to make a LED on the board itself blink. This is an initial introduction and a good way to check if the correct driver is installed and if everything is working.

If you only want to use the arduino hardware for controlling your train without delving further into the possibilities of an arduino, you can also immediately download the ArCoMoRa software. This can be found on the website arcomora.com of Nico Teering, who deserves thanks for this great package. The explanation on his website is very clear. If you prefer to purchase ready-made hardware, this can also be done through him. With the software, you can not only control your switches, but also signals, flashing lights, and monitor various things. In addition, you can also use an arduino as an occupancy detector. The setup is very simple after reading the manual.