In this tutorial, we are going to make a circuit of Long Duration Timer Using Three 555 ICs. You can make a good timer circuit by just using three 555 timers IC and some other discreet components. To increase the time duration of this circuit you can increase the number of ICs. Timer circuits are used in most electronic projects or devices so it’s good to have knowledge about how to make them in a few easy steps.
This circuit has three outputs each of which delivers a maximum of 200mA. Because it has three options of outputs it is super convenient. A relay can be connected with each output. After connecting a relay you will be able to connect any AC/DC device and control it.
Hardware Components
The following components are required to make Long Duration Timer Circuit
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | Battery | 5-12V | 1 |
| 2. | Switch | – | 1 |
| 3. | IC | NE555 Timer | 3 |
| 4. | LED | – | 3 |
| 5. | Resistors | 10K, 470Ω, 1M Var | 3, 3, 3 |
| 7. | Capacitors | Cx , 0.1µF, 1000pF | 3, 2, 2 |
| 8. | Diodes | 1N4148 | 3 |
| 9. | Connecting Wires | – | 1 |
| 10. | Breadboard | – | 1 |
NE555 IC Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of 555 Timer
Long Duration Timer Circuit
Working Explanation
The operating voltage of this circuit is 5-12V DC. All of the 555 timer ICs are wired in monostable multivibrator mode. The output of one IC is the input of the IC next to it. The last IC’s output is giving the final output, so the process will stop after the time period of the last IC is over. To automatically start this timer again you have to connect pin 3 (output) of IC to pin 2 (input) of IC1 through a 1000pF capacitor.
We are using a variable resistor of 1M ohms and an electrolytic capacitor to adjust the time duration of this circuit. If you increase the value of the variable resistor to 3M or 5M, you will be able to increase the time duration even more. The value of the electrolytic capacitor also decides the time duration of the circuit. A 100uF capacitor will provide a time period of a few minutes with each IC whereas a 1000uF capacitor will provide a time period of hours. By combining a high-valued variable resistor and electrolytic capacitor you can make a circuit with a time duration of several days.
