TUR-01: Turret home switch (touch or magnetic) - homes at START

high prioritySimulator or real robotabout 40 minTurret

• Your robot needs: Turret, and Turret home switch (touch or magnetic).
• Starter bots that fit: none (it needs parts the starter bots do not have).
• Library version: v0.17.0 or newer.
• The docs it tests: Setting up a turret, Setting up a turret.

Why

A turret's motor encoder counts from where it was at INIT. A home switch tells the turret where it really is: it turns slowly to the switch at START, and sets its angle again every time it passes it, so a slipping belt is fixed during the match. Two kinds of switch work (a touch sensor and a magnetic switch); we have tested the magnetic one.

Safety

• The turret moves by itself at START (slowly, at homingPower). Fingers and wires away from it.
• Hard stops at the wire limits. Start with homingPower = 0.2 and homingTimeout = 5.

Setup

• The switch on the robot and in the configuration: a touch sensor (e.g. REV Touch Sensor) as REV Touch Sensor, or a magnetic switch (e.g. REV Magnetic Limit Switch, a magnet on the turret) as a Digital Device.
• .homeSwitch("turret_home") on the turret's line in Robot.java, and homeAngle in Tunables.Turret (how to find it).
• Simulator: the V2 example robot (a magnetic switch at 0 degrees; commands in ILK-01).

Steps

1. Turn the turret by hand about 30 degrees away from the switch. INIT. Read the lines Turret : home switch at ... deg: found at START and Turret homing : at START it turns ... slowly to find the switch. Nothing moves in INIT.
2. START. The turret turns slowly toward the switch (homing: looking for the switch) and stops homing when it closes. Following and "aimed" wait until then.
3. Point the turret with the stick to a mark you know (straight forward). Read the angle on the Driver Station. Measure the real angle.
4. Turn the turret past the switch and back 5 times. The angle on the Driver Station stays right (the switch sets it again at each pass).
5. Unplug the switch (power off first), power on, INIT, START: after homingTimeout seconds the turret stops and the Driver Station says homing failed: switch not found. Plug it back in.
6. Rename the switch in the configuration (or leave it out): INIT says NO home switch and the start angle is used.

Pass rule

After homing, the angle on the Driver Station is within 2 degrees of the real angle (step 3) and still within 2 degrees after 5 passes (step 4), and step 5 stops within homingTimeout + 1 s (1 of 1).

Record

Write these down while you test. The report form has them as a list to fill in.

• switch kind (touch or magnetic) and how it is configured
• homeAngle, homingPower, homingTimeout you used
• the angle error after homing and after 5 passes (degrees)
• which way it turned to home, and whether you needed homeDirection
• what step 5 and step 6 showed

If your robot is different

If homing turns the long way round, set homeDirection (+1 = counterclockwise, -1 = clockwise) and say so. A turret that starts ON the switch has nothing to look for: say what the screen showed. A CR servo turret with an encoder on a motor port homes the same way: say which you have.

Report your result

Pass, fail, or could not run: every result helps. The form opens on GitHub with this test filled in (a free GitHub account is needed). No student names, please.

Report result

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