For the Almabraxas boat, I dropped the idea of using a rudder in \nfavor of a differential thruster system, because I think the rudder \ncontrol mecanism is too complex, both from the mechanical and \nwaterproofing point of view. However, since I had selected some \ncomponents, I built a control card, just for training. We can see the \nresult is quite simple. \n<\/p>\n\n\n\n\n\n\n\n
It’s really an actuator and the servo part is done “by hand” \nusing the nano. The actuator ships with a potentiometer attached to it, \nso you can sense the extension length.\n<\/p>\n\n\n\n
Although there are some small integrated linear servos (such as \nFirgelli’s), it’s more difficult to find big ones. This one can extend \nto 30cm, which you may think as big if you see what’s on the market, but\n small if you consider the need to steer an approximately 1 x 2m boat. I\n found this one through Aliexpress from Chinese company Sky Land Linear \nMotion Technology Co., Ltd., which I found very helpful and competent by\n the way. It can handle 24V, but for now I’m using only 12V, because I’m\n powering the electronic part from the H-bridge board regulator, which \ncan only work until 12V in my understanding. The actuator maximum \ntraction strength is 1000N.\n<\/p>\n\n\n\n
The H-bridge breakout board is controlled by an Arduino Nano, \nwhich reads the voltage from the actuator potentiometer, converts it \ninto centimeters and drives the motor with 2 digital lines. Note that \nthe calibration (conversion from ADC reading into mm) is different if \nthe nano is powered by USB or the board’s regulator. For this demo, it \nonly extends and retracts the servo.\n<\/p>\n\n\n\n
The display is an Olimex one. It needs both 5V and 3.3V, so the \n3.3V is provided by the Nano. On the display, you can see an arrow \nshowing the direction, the raw value read on the ADC, the conversion in \nmm, which is the actual extension of the actuator, and the target \nextension, in mm.\n<\/p>\n\n\n\n
I built the card on a simple perfboard. The breakout boards are \nmounted on headers for the sake of reusability ! Except the H-bridge \none, for which I haven’t drilled the board yet.\n<\/p>\n\n\n\n