Transistor Labs

Force-Sensitive Resistor & LED with Arduino


  1. Applications of the FSR for improving accessibility to handicapped people: accelerating/decelerating a wheelchair for paraplegics, or a pressure gauge to open doors/cabinets.

Temperature Sensor & LED Circuit with Arduino


  1. We do not need to use a voltage divider circuit with this temperature sensor because it acts as a voltage divider by changing output voltage in proportion to changes in temperature, rather than using variable resistance like potentiometers.
  2. Unlike pressure sensed by force-sensitive resistors, or rotation sensed by potentiometers, ambient temperature sensed by temperature sensors almost always changes very gradually and slowly. How does this affect the design of interactions based on this sensor? The interaction between the user and temperature sensor would not be an immediate reaction but instead a gradual, delayed response. Thus temperature sensors are not practical for prompt visualization of data.
  3. Applications of the temperature sensor: as a cooking thermometer to see the gradual change as a food cools down/heats up compared to ambient temperature, detecting the change in temperature under the hood of a car to prevent overheating.

Transistor as Switch


  1. The LED turned on by the switch is dimmer than the LED turned on by the transistor because the LED connected to the switch has higher resistance of 10kΩ, as opposed to 560Ω resistance in the other LED.
  2. Ohm’s Law: Iswitch leg = V/R = 5V/10kΩ = 0.5mA.
    Itransistor leg = V/R = 5V/560Ω = 8.9mA.

Transistor as Amplifier


  1. How does turning the potentiometer to maximum resistance affect the sensitivity of the circuit to the photo-resistor’s signal, as compared to turning the potentiometer all the way to minimum resistance? Turning the potentiometer to maximum resistance lowers the sensitivity of the photo-resistor as less voltage flows through the circuit, whilst minimum resistance increases the sensitivity of the photo-resistor.

Transistor Controlled by Arduino

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