Wiring the Control System and Motors

Electrical problems cause a large share of robot failures, and most of them come from loose connectors, pulled cables and messy wiring rather than broken electronics. Wiring carefully the first time saves hours later. In this lesson you will connect the control system, install motors and tell the robot which motor is which.

The power path

1. 1
   Battery

   A 12 V rechargeable battery pack supplies all the power. It includes a fuse that protects against short circuits. Use only batteries the current Competition Manual allows.
2. 2
   Main power switch

   The battery connects to a main switch that turns the whole robot on and off. Mount it where a referee or teammate can reach it quickly.
3. 3
   Control Hub

   From the switch, power goes into the Control Hub. The hub is the robot's brain: it runs your code and powers the motor and servo ports.
4. 4
   Motors

   Each drive motor plugs into a motor port, numbered 0 to 3 on the Control Hub. Its encoder cable plugs into the matching encoder port.
5. 5
   Expansion Hub (later)

   If you need more than four motors, an Expansion Hub can be added and connected to the Control Hub. You do not need one for a basic chassis.

Installing motors

A motor must be held so it cannot rotate, tilt or slide, because every bit of movement turns into binding or a loose wheel. Use the motor mount designed for your kit and the screws it specifies. Mount all four drive motors the same way so they behave the same.

• Mount the motor flat against its bracket and tighten the screws evenly.
• Check the motor shaft lines up with the wheel shaft or gear it drives.
• Do not let the motor body carry the robot's weight on its own if your kit offers extra support.
• Keep the motor's cable exit pointing toward where the cable will run, not toward a wheel.

Motor cables and ports

Cable management and strain relief

Cables must never touch wheels, gears or moving mechanisms, and they must never be the thing holding a connector in place. Strain relief means fixing the cable to the frame a short distance from the connector, with a little slack, so that if the cable is pulled the zip tie takes the force instead of the plug.

• Route cables along the frame and secure them with zip ties every 10-15 cm.
• Leave a small loop of slack near each connector, then tie the cable down just behind it.
• Bundle the cables from one motor together and keep them away from sharp edges.
• Label both ends of each cable, for example FL, FR, BL and BR.
• Leave the Control Hub's ports and the battery connector easy to reach for repairs.

Configuring motors

1. 1
   Open the configuration

   Connect the Driver Station to the Control Hub, open the menu and choose Configure Robot, then create a new configuration.
2. 2
   Pick the hub

   Select the Control Hub Portal, then the Control Hub, then Motors.
3. 3
   Set each port

   For ports 0 to 3, choose the motor type that matches your motor and type a name such as frontLeft. Names are case-sensitive.
4. 4
   Save and activate

   Save the configuration with a clear name and make sure it is the active one.

1package org.firstinspires.ftc.teamcode;
2
3import com.qualcomm.robotcore.eventloop.opmode.LinearOpMode;
4import com.qualcomm.robotcore.eventloop.opmode.TeleOp;
5import com.qualcomm.robotcore.hardware.DcMotor;
6
7@TeleOp(name = "Chassis Motor Test")
8public class ChassisMotorTest extends LinearOpMode {
9    @Override
10    public void runOpMode() {
11        DcMotor frontLeft = hardwareMap.get(DcMotor.class, "frontLeft");
12        DcMotor frontRight = hardwareMap.get(DcMotor.class, "frontRight");
13        DcMotor backLeft = hardwareMap.get(DcMotor.class, "backLeft");
14        DcMotor backRight = hardwareMap.get(DcMotor.class, "backRight");
15
16        // Left-side motors face the other way, so reverse them
17        frontLeft.setDirection(DcMotor.Direction.REVERSE);
18        backLeft.setDirection(DcMotor.Direction.REVERSE);
19
20        waitForStart();
21
22        while (opModeIsActive()) {
23            // Hold one button to spin one motor at 30% power
24            frontLeft.setPower(gamepad1.x ? 0.3 : 0.0);
25            frontRight.setPower(gamepad1.y ? 0.3 : 0.0);
26            backLeft.setPower(gamepad1.a ? 0.3 : 0.0);
27            backRight.setPower(gamepad1.b ? 0.3 : 0.0);
28
29            telemetry.addData("FL ticks", frontLeft.getCurrentPosition());
30            telemetry.addData("FR ticks", frontRight.getCurrentPosition());
31            telemetry.addData("BL ticks", backLeft.getCurrentPosition());
32            telemetry.addData("BR ticks", backRight.getCurrentPosition());
33            telemetry.update();
34        }
35    }
36}