Sensors for use in this class.

Sensors 2Robotics: Bridgewater state college.

Sensors for this class

● Now that we've covered sensors commonly used– Lets look at the sensors available for this class.

● We are using two robot controllers in this class– Handyboard

– Lego RCX

– Lego simpler but less powerful● Will use handyboard for first lab, Lego for second. Projects

as they come.

– Discuss sensors separately Handyboard today.

Handyboard

Photodiode (light sensor)● Omni-directional light

sensor– Low values for lots of light

– High values for little light.

– Make directional by wrapping in aluminum foil.

– Add two or three and can get direction information about light sources.

– Analog ports 2-6

IR reflectance sensor● IR reflectance

– “top hat”

– Active sensor emits IR radiation and detects it in same direction.

– “active range” (min range) of 2 cm; max range depends

– Point at nothing? Return high value; point at light colored close obj, return low value.

– Generally edge detection

– Black/white line following.

– Analog ports 2-6

IR Range Sensor (E.T head)

● IR Range sensor– Active sensor emits IR radiation and

reads the reflectance back.

– Effective range is 6-30 inches

● Objects farther away give lower return values. Closer to 6 inches gives higher return values.

● Closer than six inches and the return values decrease again

● Analog ports 16-20

Touch/contact Sensors

● Digital Sensors– Help simulate a sense of touch.

– 1 when pushed, 0 when not.

– Button: push button in.

– Lever switch: push on lever

● Very slight force required– Post switch, push in or sideways.

– Together primitive sense of touch

– actuator/effector limit switch.

– digital ports 7-15

Break-beam encoder

● Digital encoder sensor– Sends 1 when IR signal between

two poles is broken, else 0.

– Generally used as digital encoder ● Use gear or wheel with hole in it

to encode how many times the hole passes through the beams area.

– With software support can develop a speed/distance encoding.

– Encoder 0: digital port 7, encoder 1 digital port 8.

Handyboard sensors

● Selection of inexpensive analog and digital sensors– No soldering required

– Color, light and proximity detection

– Touch at a variety of distances from the robot● Lever very gentle, post fairly gentle.

– Encoder capable of recording how many times a particular act was done.

– Basic sensing with lots of potential.

Lego RCX Brick

Lego Light Sensor

● Lego light sensor– Enhanced light sensor

● LED emits small amount of light, then sensor detects light.

– Duel use● Point down: color detection● Point out: proximity detection.

– Return values 0-100● Some toolsets 1-100

Lego Touch Sensor

● Lego touch bump sensor– Basic on/off digital sensor

– Small bump area

– Use Lego pieces to provide a larger bumper for sensor.

Lego Temperature Sensor

● Temperature sensor– Thermometer

– Measures temperature in F or C

– Range from -20 to +70 C● -3 to +157 F

– Depending on language used, can get temperature in degrees, tenths, or raw values (0 to 1023).

Lego Rotation/Angle Sensor

● Rotation sensor– Gives rotation position and

counts rotations.

– Has resolution of 22.5 degrees (16 positions)

– Can record rotation either forward or backward.