the robot cuts out for a second in the middle of a match when we run the intake and drivetrain at the same time

When running multiple systems like the drivetrain and intake simultaneously, the robot may experience power or control issues due to high current draw. FTC motors can have a stall current as high as 11 amps per motor, while FTC batteries can only provide 20 amps of current output before a fuse is likely to blow . Drawing too much current, or stalling more than two motors at the same time, can cause other motors to become sluggish or unresponsive .

Additionally, motors pull a large amount of "transient current" for extremely brief periods when they start moving or experience a momentary load . While these transients generally do not pop a fuse, they can cause low voltage or sluggish control .

If the robot is experiencing a temporary disconnect where it cannot be controlled from the gamepad, this can be caused by improper wiring, loose cables,

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Motor Power > Note on Current Consumption

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You may see while looking at motor curves that the stall current of FTC motors can be as high as 11 amps per motor. FTC batteries can only provide 20 amps of current output before blowing the fuse is likely. However, even if the 20 amp limit isn't reached, drawing too much current can cause other motors to feel sluggish or unresponsive. Care should be taken to ensure that more than two motors are never stalled at the same time.

Note: You may be able to ignore this when dealing with mecanum drivetrains, as they will generally slip before the motors actually reach their stall current. However, placing very low gear ratios or more than 4 motors on traction drivetrains can exceed the current limit of an FTC battery.

Motors can pull "transient current" where they pull a large amount of current for extremely brief amounts of time. This often happens when the motor starts moving or when a momentary load is placed on it. While transients generally cannot cause a fuse to pop, they can cause other issues, such as sluggish control if pulled by a motor, or low voltage if the transient is pulled by a servo (goBILDA Super Speed servos have been observed to do this occasionally).

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Software Glossary

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Disconnect — A disconnect (DC) is when, for any reason, the robot is not able to be controlled from the gamepad. This can happen for many reasons - static buildup on the robot, a loose cable, or an error in code.

Generally, most DCs are caused by improper wiring, so wire stress relief is encouraged for all teams (USB Retention Mount). They can also be caused by WiFi disconnects, or an ESD (electrostatic discharge) shock to the electronics.

Driver Station — The Driver Station (DS) refers to both the software and device that is used by the drive team and connects to the gamepad(s). The device can either be one of the Android phones specified in Game Manual Part 1 or a REV Robotics Driver Hub.

Robot Controller — The Robot Controller (RC) refers to both the software and device that is on the robot that controls it. This can either be a REV Robotics Control Hub or one of the Android phones specified in Game Manual Part 1 connected to an Expansion Hub via a Micro USB cable.

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Control Systems > REV Control Hub + REV Expansion Hub

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Warning: It is of vital importance to update the firmware on REV Expansion hubs to at least version 1.8.2. It includes better protection against disconnects and improves program performance. See the REV Expansion Hub firmware update docs.

This is the standard control system for teams starting out in FTC.

The Control Hub connects to the Expansion Hub through either a RS-485 connection, or a USB-A (Control Hub side) to mini-USB (Expansion Hub-side) connection. In either case, proper strain relief and cable management should be used.

For more information on setting up the Control Hub and configuring the robot, head to REV Robotics' Technical Resources Control Hub Guide (https://docs.revrobotics.com/duo-control/control-hub-gs).

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SDK Motors

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The SDK offers several methods of controlling and communicating with motors, as well as a couple of hidden methods that can be easily accessed.

All motor ports are controlled with what is called an H-bridge motor controller, a circuit that can be used to vary the output voltage as well as signage (negative or positive) of the voltage. Negative voltage through a DC Motor reverses a motor, whereas positive motor will make the motor go forward. SDK Motor power (from -1 to 1), represents a multiplier of the input voltage that is output through the motor port. The different voltages are created via PWM, where the port is turned on and off rapidly to create a lower average voltage.

In addition, the zero power behavior of the motor, that is the behavior of the motor when no power is applied, can be configured. In FLOAT mode, the motor controller simply turns off, providing minimal additional resistance. In BRAKE mode, the two motor leads are shorted together internally. Due to the inherent property that all DC brushed motors generate electricity when the shaft spins, shorting the leads causes a reverse power that stops the motor quickly and is resistant to external forces.

Note: The motor controller uses the input voltage, this means on a 13 volt battery, setting the power to 1 will create an output voltage of 13 volts. Similarly, on an 11 volt battery, a power of 1 will create an output voltage of 11 volts.

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CAD Tutorials > CAD Tutorial Part 1 - Drivetrain in an Hour > Additional Considerations

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Powering wheels can be done is a couple different ways through either belts and pulleys, chains and sprockets, gears, or even powered directly from the motor. Direct drive and chains are the simpler of the options, with direct drive not needing a calculated distance at all just have to set the motor exactly where the center of the wheel is. Chains allow for a little bit of slack not needing an exact center to center distance in the wrap like belts and pulleys do. Finally gears which need to be a certain distance apart from each other to mesh properly and not skip or bind.

Mounting motors is done in a plate style by face mounting the motor into the innermost drivetrain plate. It can also be done by mounting the motors to a 3rd plate, located in between the outside and inside. This allows for the motor to take up less space in the middle of the robot, but adds complexity. Motors should always be as low as possible and depending where you want the center of mass, either the middle or towards the back of the robot. It is also worth keeping in mind the type of power transmission and the expediency of doing so in light of the motor placement.

Ground clearance is all dependent on if there are any obstacles on the field, as well as what your team wants to do in that game in regards to said obstacles.

For example, in Rover Ruckus some teams with tank drivetrains decided to enter the crater. Therefore, they left enough space to not beach themselves on top of the crater, a common mistake that inexperienced teams often make.

Other teams decided to ignore driving over the crater and decided to reach over with an arm or slide system, which meant they didn't need a lot of ground clearance for their drivebase.

Typically, anywhere from .25 inches of clearance to .5 inches (if you want to be safe) on a completely flat field will allow for the weight of the robot to push into the foam tiles. Nothing else from the robot should touch the ground.

Something you can do is set the robot in CAD onto a field. Set up obstacles such as the crater and simulate driving over the crater by moving it across like you think it would in the real world.

If either of the plates intersect with the obstacle, add some more clearance so you don't get beached like a sad whale.

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Motor Guide

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12 volt DC motors are main drivers of FTC® robots. They are used for powering the drivetrain, intakes, lifts, and other mechanisms.

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