ucsd-creative-robotics

Sensors with the Dev Board

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Switch

Bump/contact sensor [TK]

Photoresistor

Light sensor

https://www.arduino.cc/en/Tutorial/BuiltInExamples/AnalogInput

• Use a multimeter to see how the resistance changes with the photoresistor.
  • (this does not need a circuit. connect the red lead to one side of the photoresister, and the black lead to the other)
• We can put a photoresistor in series with a resistor to make a voltage divider. This is similar to how a potentiometer works. As the resistance of the photoresistor changes (the light changes), the output voltage will change.
• Hook up the circuit in the picture above with a resistor, photoresistor, and wires to ground, 5V, and A0.
• Use AnalogReadSerial from the section above, and use the serial port monitor to see what the range of output voltages is.
• Activity: Use the photoresistor to control the servo from last class, in place of the potentiometer
  1. Use the serial port to debug the range of analog values coming in from the photo-resistor/resistor voltage divider.

Ultrasonic Rangefinder

• Install the HCSR04 library (Tools->Manage Libraries->Search for “HCSR04”)
  • 
• Try the File->Examples->HCSR04->simple example.

NOTE❗❗: Change the line that initializes the sensor to use pins 12 and 11 from:

UltraSonicDistanceSensor distanceSensor(13, 12);  // Initialize sensor that uses digital pins 13 and 12.

to

UltraSonicDistanceSensor distanceSensor(12, 11);  // Initialize sensor that uses digital pins 12 and 11.

(shown in the diagram above)

HC SR04 Timing Diagram

Infra-red (IR) Rangefinder

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Capacitive Touch Sensing

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Thermistors

• Good adafruit tutorial: https://learn.adafruit.com/thermistor/using-a-thermistor
  • including more about voltage dividers: https://learn.adafruit.com/thermistor/using-a-thermistor#analog-voltage-reading-method-2917724
• Demo: How a thermistor changes resistance with changes in temperature

Temperature and Humidity

1) Install DHT11 Library: Tools -> Manage Libraries -> search for DHT11 by Dhruba Saha.

• 2) Try Examples -> DHT11 -> Read Temperature 3) Wire up circuit (confirm Elegoo DHT11 pinouts before powering on, DATA/OUT should go to Arduino D2)

• 

DHT11 Protocol from (https://www.ocfreaks.com/basics-interfacing-dht11-dht22-humidity-temperature-sensor-mcu/)

Temperature Sensor

NOT IN ELEGOO KIT

(image from Adafruit)

• The TMP 36GZ is a temperature sensor.
• This is an active sensor, meaning we provide power to ground and 5V, and it outputs a voltage proportional to temperature.
  • Looking at the datasheet, we see it is 10mV/degree Celsius. That means we can use the output voltage (read by analog in) to figure out what the temperature is.
• To convert from AnalogRead value to milli-volts: Voltage at pin in milliVolts = (reading from ADC) * (5000/1024)
• To convert from milliVolts to degree celsius: Centigrade temperature = [(analog voltage in mV) - 500] / 10
• Activity:
  • Use AnalogReadSerial to figure out what the current temperature in the room is in Celsius.
  • Modify your code to convert Celsius to fahrenheit.
  • Explore the dynamic behavior: how quickly does it change in response to breathing on it? In response to touching it? Can you get the temperature to go up, or go down?

Capacitive Touch Sensing

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References

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