One of the most widely used and adaptable integrated circuits in electronics is the IC 555.
It can function in a number of modes, including bistable, astable and monostable configurations.
In this project, we will use the IC 555 in monostable mode to build a easy DIY timer alarm circuit.
With this circuit, you may program a timer to run for a specified amount of time, after which a buzzer or alarm will sound.
When it comes to chores that need timed reminders, this can be helpful.
Circuit Working:
Parts List:
| Component | Specifications | Quantity |
|---|---|---|
| Resistors | 100Ω | 1 |
| 20k | 1 | |
| 470k | 1 | |
| 1M | 1 | |
| 1.5M | 1 | |
| 2.2M | 1 | |
| Capacitors | Ceramic 0.1µF | 1 |
| Electrolytic 470µF | 1 | |
| Semiconductors | IC 555 | 1 |
| Buzzer | – | 1 |
| Switches | On/Off switch | 5 |
| Push button (start switch) | 1 | |
| Battery | 9V | 1 |
The IC 555 is in its idle state when SW1 is used to turn on the circuit.
One of the switches SW3 to SW6 is closed to select the required timing period.
This joins the timing circuit to the matching resistor.
The IC 555 is activated by grounding its TRIG pin (pin 2) when the Start switch SW2 is pressed.
Through the chosen resistor, the capacitor C2 begins to charge.
The buzzer remains silent throughout the timing interval because the IC 555 output pin 3 becomes high.
The buzzer is triggered by the IC 555 output going low when the capacitor has charged to two thirds of the supply voltage.
Press the Start switch once again after choosing a new timing interval or turning off the power to reset the timer.
Formulas and Constructions:
Below mentioned are the formula and calculations for Timer Alarm Circuit using IC 555.
The timing duration T for the circuit can be calculated using the formula:
T = 1.1 × R × C
where,
- R is the resistance value selected by the switches R3 to R6.
- C is the capacitance value C2.
Calculations:
For R = 470 kΩ and C = 470 µF
T = 1.1 × 470,000 × 470 × 10^-6 = 242.99 seconds = 4.04 minutes.
How to Build:
To build a Easy DIY Timer Alarm Circuit with 555 IC you need to follow the below mentioned steps for connections and assembling:
- Gather all the components as mentioned in the above circuit diagram.
- Connect pin 1 of IC1 555 to GND.
- Connect pin 2 of IC1 555 to one terminal of pin 4 and other terminal of pin 2 to GND through SW2 start switch.
- Connect pin 3 of IC1 555 to 9V positive supply through resistor R1 and buzzer.
- Connect pin 4 of IC1 555 to 9V positive supply.
- Connect pin 5 of IC1 555 to GND through capacitor C1.
- Connect pin 6 of IC1 555 to pin 7.
- Connect pin 8 of IC1 555 to 9V positive supply.
- Connect switches SW3 to SW6 and select the timing interval by changing the resistance connected to the circuit.
- The timing intervals are determined by R3 to R6 resistors and the capacitor C2.
- Connect SW1 switch one pin from positive supply and the other pin to 9V battery positive supply and connect the negative supply of 9V battery to GND.
Conclusion:
The IC 555 is used in this easy DIY timer alarm circuit, which is very practical for timing purposes and easy to build.
You can adjust the timing duration to your requirements by changing the resistors and capacitors.
For those who are new to electronics, this project is ideal for learning how the IC 555 operates in monostable mode and investigating its practical uses.