WEBVTT
Kind: captions
Language: en

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♪ Control ♪

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Hello.

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We're demonstrating 
an on/off servo control system

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using a Smart Magnetometer,
with a magnet on the actuator

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a Smart Angle Sensor 
underneath the magnetic knob,

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and an Arduino board.

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We have a three-position solenoid valve,

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but these valves don't release pressure 
when they're off,

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so the actuator tends to drift.

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Our control moves the cylinder

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when the position is outside 
a deadband.

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The angle sensor detects 
the rotation of a magnetic knob

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and sets the desired position.

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The magnetometer's sensitivity and wide range

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gives us control over 
about a 50-millimeter range.

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This valve provides on/off control 
like a thermostat.

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We could have smoother control with a 
proportional flow valve,

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but those valves are a lot more expensive.

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Here's a diagram:

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Both sensors have SPI interfaces,

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so we just connected them in parallel
with different Slave Selects.

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The Arduino drives the valve solenoids

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via transistors.

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Here's the Arduino program:

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There's a procedure 
for reading the sensors,

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which is a simple four-byte sequence.

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We read the angle sensor

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and the magnetometer.

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For this demo we use a simple 
inverse square root approximation

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for distance as function of field.

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For better accuracy, we could 
calibrate a piecewise linear lookup table

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as we demonstrated in another video.

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The cylinder is moved in or out
if the error is beyond the deadband tolerance.

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Here are the demo components 
and where to get them:

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Click, e-mail, or call
for more information,

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or to buy Smart Sensors,

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breakout boards, or evaluation kits.