Using sensors

[Bronson]

Our team is trying to find out what sensors we would like to use, and how to use them correctly. Anybody have any ideas?

[tseres]

limit switches? gyros? encoders? potentiometers? accelerometers?

if you have any questions, let me know!

[Lucretius]

I know what potentiometers are (variable resistors), but what do they have to do with robotics? How are they useful?

[etphonehome]

potentiometers (aka pots) can be used to measure how far your rotating device, whatever it is, has swiveled
very useful to create coded limits so that an arm doesn't overextend or swivel to far, which strains or snaps wires
also useful to know exactly how fast something is rotating

[artdutra04]

Here are a few brief summaries of some common types of sensors used in FRC applications:


Limit switch: can be used for simple control of manipulators, to prevent them from driving past the mechanical limits of the system. Digital signal.

Light sensor: can be used to follow lines, detect colors, and be used to create an optical encoder to sense rotation by pointing it at a disc with alternating white and black stripes. Analog signal.

IR range sensor: used to measure distance. Analog signal.

Ultrasonic sensor: used to measure distance. Needs interrupts to work correctly.

Hall effect sensor: detects ferrous materials, such as the teeth on a steel gear or sprocket. Can be used to sense gear teeth passing by, to work as an encoder. May need interrupts.

Encoder: generic term for sensor that measures rotation; with a known wheel size can be used to gauge how far robot has driven/spun. Generally needs interrupts to work correctly.

Quadrature Encoder: Basically it's a "dual encoder" that can sense rotation as well as which direction it is rotating in.

Accelerometer: measures acceleration. Can be used to find abrupt changes in speed, or for inertial navigation.

Gyro: measures change in angle. Can be used in place of potentiometer if space to mount one is not available. Can also be used to sense how far a robot has turned.

Potentiometer: Variable resistor used to detect rotation over a limited range, commonly about 270^o. Can be used on arms, to know exactly where the arm is. Analog signal.

[JATO]

Since 2008 OverDrive Challenge seemed to emphasize automous or semi-automous behavior....

What about using the Limit switches to detect collision with a wall and a sub program to tell the robot to turn and back up a bit, then try to move forward again?? Could help your robot autonmously move around the Track? couldn't it?

thinking about 2 limit switches 1 left and 1 right.

IF left switch is triggered, then backup and turn right 10 degrees, then continue forward.
IF right switch is triggered, then backup and turn left 10 degrees, then continue forward.

If your Robot gets in a real jam, send it a specific command via the IR remote to turn, backup, or return to full-autonmous mode.

Our Team hasn't worked on this YET, but I'm gonna pitch it to our Control and Programmer at our next meeting.