Force-sensitive Resistor and LED with Arduino
Give ideas of 2 applications of this sensor in the field of improving accessibility for handicapped people.
- For people in wheelchairs, FSRs could be embedded in tiles in front of doors in order to trigger servos to open the door.
- FSRs could be used in order to control a servo for lifting objects. The power of a circuit is measured in Watts and Watts = Voltage * Current. Since FSRs influence the current in circuits, pressure sensors can be used to perform lifting of objects based on how hard a handicapped person is pushing on the sensor.
Temperature Sensor and LED circuit with Arduino
(the temperature difference between the window and the rest of the room was pretty drastic that day)
- We use a voltage divider circuit for potentiometers, force-sensitive resistors, and many other sensors. Why do we not need to use a voltage divider circuit with this temperature sensor?
- Because a temperature sensor essentially is a potentiometer just like FSRs and other sensors.
- 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?
- FSRs or rotation sensed by potentiometers are very useful when intercting with people, since people can elicit a direct response from the prototype. A design relying on temperature sensors could be used for the prototype to interact with the environment, rather than a human being. This is because the gradual change does not give the user instant gratification.
- Given the range of temperatures at which this sensor works, please give 2 ideas for applications of this sensor. Applications may involve anything from scientific research to artistic endeavors, but they should necessitate the use of this sensor, as opposed to other sensors.
- professional coffee brewing requires the perfect water temperature. A temp sensor could be used to control a hot plate, ensuring consistant water temperatures.
- during my final exams in high school I always wondered how much the room temperature was changing during the course of long exams as all students were concentrating and producing heat. A temperature sensor could record the data and through a serial connection this data could be fed to python for algorithmic manipulation. This data could the be outputted to a speaker to create a song/audio art project.
Transistor as a Switch
(it is very hard to see but the other LED is lighting up dimmly)
- Why is the LED turned on by the switch dimmer than the LED turned on by the transistor?
- because the current is running through a 10kΩ resistor before reaching the LED. In the "high power line" there is only a 560Ω resistor, resulting in a higher current reaching the LED.
- Give the approximate current flowing through each leg of the circuit (ignore any affect the transistor might have on the current flow or voltage drop).
- high power line:
- initial current = 5V
- resistor = 560Ω
- using Ohm's law we can solve fore I (current)
- 5V = I * 560Ω
- 5V/560Ω = I
- 8.92mA = I
- switch line:
- initial current = 5V
- resistor = 10kΩ
- 5V = I * 10kΩ
- 5V/10kΩ = I
- 0.5mA = I
Transistor Amplifier
- 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?
- The wire going into the transistor to activte/"zap" is placed between two resistors. Thus, we have to use the voltage diver formula (Vout = Vin(R2/(R1+R2))) to understand how turning the potentiometer to a maximum or minimum affects the circuit.
- at a maximum, R1 is at 20kΩ, decrasing the ratio of R2 to R1. Thus, the circuit is less sensitive to the photo resistor's signal.
- at a minimum, R1 is at 10kΩ, increasing the ration of R2 to R1. Thus, the circuit is more sensitive to the photo resistor's signal.
Transistor Controlled by Arduino
Arduino as a switch
Arduino as an amplifier
