We use an Arduino UNO to control our OTV.
Along with the Arduino, we use:
1x Continuous servo motor move our OTV's arm up and down.
1x Ultrasonic sensor to use in navigation.
1x Reed switch to detect magnetism.
2x 12V DC motors for propulsion.
1x L298N Dual HBridge Motorcontroller to controller our 2 motors.
For duty cycle detection, we will use brass wool.
To power our OTV, we decided to use a 12V rechargable battery. This battery has a kill switch attached. The battery has a 2000mAh capacity and a recommended discharge rate of 2A.
Our current draw calculations are as follows:
Motors: Our calculated current draw for each motor is ~147.3 mA per motor, which is calculated based on our 18.7 Ncm operating torque. Using this torque and our 90 rpm operating speed gives us a wattage of 1.767 W, which diving by 12 V and converting from A to mA gives us an operating current draw of ~147.3 mA per motor, or 294.6 mA for both motors.
Ultrasonic: 15 mA while operating. (Source: link).
Reed Switch: The reed switch's current draw is negligible, and the reed switch is only operating for a small part of our mission, so we will not include this in our calculating.
Servo motor: The arm servo has an operating current draw of 100 mA, though it could fluctuate higher. (Source: Manufacturers' Website).
Motorcontroller: The L298N Dual HBridge uses 36 mA for functions not related to powering the motors themselves, according to Banana Robotics.
WiFi Module: According to source, the ESP8266 can draw up to 170 mA.
The total current draw based on all components is ~615.6 mA. Based on our battery's 2000mAh capacity, our OTV should be able to run for around 3.25 hours.
We will modulate power to our propulsion motors using a L298N Dual HBridge motorcontroller, as stated above. This motor controller has a discharge rate to the motors of 2A, the same as our battery. The L298N will take a PWM signal from the Arduino to control the speed of the motors. The arm servo's direction and speed will also be controlled using a PWN signal from the Arduino.
2: Propulsion: Direction B 1
3: Ultrasonic TX
4: Ultrasonic RX
5: Arm Servo Signal
6: Propulsion: Direction A 2
7: Propulsion: Direction A 1
8: WiFi RX
9: WiFi TX
10: Propulsion: ENA
11: Propulsion: ENB
12: Duty Cycle
13: Propulsion: Direction B 2
A0: Reed Switch (read as digital input in code)
HBRIDGE: IN1 = DirA 1; IN2 = DirA 2; IN3 = DirB 1; IN4 = DirB 2
OUT 1-4 to motors
The battery is connected to the breadboard, creating a 12V rail. Ardunio Vin will connect to this rail. The other breadboard rail will be 5V from Ardunio's 5V out.
The sensors/actuators connect to the rails as follows:
Ultrasonic Sensor to 5V rail.
Arm Servo to 5V rail.
WiFi module to 5V rail.
Reed Switch Module to 5V rail.
Dual HBridge Motorcontroller to 12V rail.
All of these components will also be connected to (any) ground rail.