The Sunrise Wake-Up Alarm
by Robotics team in Circuits > Electronics
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The Sunrise Wake-Up Alarm
Sunrise is an alarm clock, that simulates the sunrise to ensure a soft and natural wake up. The advantage of a progressive light clock over traditional alarm clocks is the positive effect on stress level, drowsiness and well-being.[1]
Alarm Circuit Schematic
A schematic is a diagram of a circuit. Schematics use symbols to represent circuit components and lines to show the connections between components.[2]
Electronic schematics are like recipes for electronics. They are also called circuit diagrams.[3]
I used KiCAD and TinkerCAD to draw the sunrise wake-up alarm circuit schematic. It’s a light-sensitive circuit that will activate a buzzer when you have light shining directly on it. Place it in your window at night and the alarm will activate in the morning when the sun rises.[4]
Analysis (How Transistor Work)
The transistor is like an electronic switch
and to turn the transistor on, we need about 0.7v from the base to the emitter and a small current going from the base to the emitter.
When the transistor is on:
1. A larger current flows from the collector to the emitter.
2. The buzzer gets activated.
Let's do some analyzes on TinkerCAD, I will make the intensity of light constant and change the resistor.
First Analysis
R= 50 ohm.
We notice from the simulation when R=50 that
1. The volt between the base and the emitter is 0.511 v ( less than 0.7 v)
2. This volt is made transistor off and this means that no current will flow from the collector to the emitter
3. The buzzer is deactivated, because the current flows in the buzzer equal zero.
Second Analysis
R= 70 ohm
We notice from the simulation when R=70 that
1. The volt the base to the emitter is 0.640 v
2. This volt is less than 0.7 but this make the small current flows from the collector to the emitter.
3. This small current (1.42 mA) turns on a buzzer, but the sound of a buzzer is low.
Third Analysis
We notice from the simulation when R=100 that
1. The volt the base to the emitter is 0.718 v
2. This volt is greater than 0.7 and this make a transistor on and a larger current flows from the collector to the emitter.
3. This larger current (14.9 mA) turns on a buzzer with the sound is high.
Principle of Working
The photoresistor and the resistor make up a voltage divider.
When it’s dark, the photoresistor will have high resistance (higher than Resistor). That means the voltage divider gives a low voltage out to the base of the transistor and it stays off. When the transistor is off, the buzzer is deactivated.[4]
When there is a lot of light on the photoresistor it will have low resistance. This will give a higher voltage out to the base of the transistor so that it turns on. This means the buzzer gets activated and starts making sound.[4]