What is an On/Off Delay Timer?
On/Off Delay timer Circuits are simple electronic circuits that can either turn ON or OFF a circuit after a predetermined time period has passed. The use of timers in electrical and electronics is mainly focused on creating controlled delays in circuit operations. Timers can be classified into three major types. On Delay timer, off delay timer & star delta timer. In today’s tutorial, we are going to go over a step by step process on how To Make an On/Off Delay Timer Circuit using NE555 precision Timer IC.
555 Timer IC
NE555 is a precision timing circuit capable of producing accurate time delays or oscillation. A NE555 has three basic modes of operations. In the time delay or mono-stable mode of operation, the timed interval is controlled by a single external resistor and capacitor network. In Bi-stable mode, the output can be configured to latch on a certain voltage level for an indefinite period of time and can be sent back to the zero states by resetting the IC. For an a-stable mode of operation, the frequency and duty cycle can be controlled independently with two external resistors and a single external capacitor.
Here the NE555 timer acts as a monostable multivibrator. A monostable multivibrator (MMV) often called a one-shot multivibrator, is a pulse generator circuit in which the duration of the pulse is determined by the R-C network, connected externally to the555 timers. In such a vibrator, one state of output is stable while the other is quasi-stable (unstable). For auto-triggering of output from a quasi-stable state to a stable state, energy is stored by an externally connected capacitor to a reference level. The time taken in storage determines the pulse width.
Hardware Component
You will need the following parts to build this project
| S.No | Component | Value | Qty |
|---|---|---|---|
| 1) | Timer IC | NE555 | 1 |
| 2) | LED | 5mm, 3.5V | 1 |
| 3) | Capacitor | 10uF, 100nF | 2 |
| 4) | Potentiometer | 10K | 1 |
| 5) | Resistor | 10K | 2 |
| 6) | Soldering Iron | 45W – 65W | 1 |
| 7) | Soldering Wire with Flux | – | 1 |
| 8) | DC Battery | 9V | 1 |
| 9) | Battery Clip | – | 1 |
| 10) | Veroboard | – | 1 |
| 11) | Jumper Wires | – | As per need |
NE555 Pinout
Useful Steps
1) Solder the NE555 time IC on the veroboard.
2) After that, solder a 10K resistor between pin 6 of the IC and the 10K pot. After that, solder a 10K pot between pin 7 of the IC and the 10K pot.
3) After that, solder another 10K resistor with pin 7, 4, and 8 of the IC.
4) Short pin 2 and pin 6 of the IC.
5) After that, solder a 100nF capacitor between pin 5 and pin 1 of the IC.
6) After that, solder the +ve pin of the 10uF capacitor with pin 6 of the IC and -ve pin with pin 1 of the 555 timer IC.
7) Solder the -ve pin of the LED with pin 3 of the timer IC and +ve pin with pin 4 and 8 of the IC.
8) After that, solder the -ve pin of the battery clip with pin 1 of the IC and +ve pin with pin 8 of the IC.
9) Power up and test the circuit using a 9V Battery.
Working Explanation
The working of this circuit is actually pretty simple. Here, we are using the NE555 timer in monostable multivibrator mode. In order to set the ON/OFF duration of the circuit, we can set the preset 10K pot to the desired value of resistance. This will allow us to set the trigger duration and the threshold voltage for the 555 timer.
ON powering up the circuit the RC constant associates a set value to the trigger pin of the 555 timer. When the trigger value of the timer is well above the threshold, the 555 timer either stops or opens the output to the indication LED.
Application
- It commonly serves as a protection circuit to protect any electrical or electronic equipment and appliance from sudden high or unstable voltage such as voltage stabilizer for the fridge, UPS & PCs.
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