In many homes and industries sometimes a fan does not turn ON immediately.
A fan start delay timer is a circuit that delays the fan start.
When power is applied the fan stays OFF and after some fixed time the fan turns ON automatically.
In this circuit the delay time is about 10 seconds and however, it can be changed easily.
This is useful to protect devices and is also helpful for automation systems.
No IC is used, the circuit uses transistors and other components, where the input supply is 12V DC.
This Fan Start 10 Second Delay Timer Circuit is cheap and easy to build.
Circuit Working:
Parts List:
| Components | Values | Quantity |
|---|---|---|
| Resistors | 22k, 220k, 1k | 1 each |
| Capacitor | Electrolytic 1000uF 25V | 1 |
| Semiconductors | Transistors BC547 | 2 |
| 5mm Red LED | 1 | |
| Diodes 1N4007 | 3 | |
| Zener Diode 5.1V 1N751 | 1 | |
| Relay 12V DC | 1 | |
| ON/OFF Switch | 1 | |
| Power Supply 12V DC | 1 | |
| 12V DC Fan | 1 |
First of all, switch S1 is turned ON and then 12V DC is applied to the circuit.
Initially, the capacitor C1 is fully discharged and so transistor Q2 does not conduct.
Because of this the transistor Q1 also remains OFF.
Therefore, the relay stays OFF and hence the fan connected to the relay remains OFF.
Now slowly capacitor C1 starts charging and it charges through resistor R2.
This charging takes time and this time decides the delay period.
After some seconds the voltage across C1 increases and when it reaches about 5.1V Zener diode conducts.
Then the base current flows into transistor Q2 and as a result Q2 turns ON.
After that the transistor Q1 also turns ON and then the relay energizes.
So the relay contacts switch and finally the fan turns ON after 10 seconds delay.
Meanwhile, the diode D3 protects the transistor from relay back EMF and also the LED1 shows power or working status.
How to Build:
To build a Fan Start 10 Second Delay Timer Circuit following steps are required for connection:
- Assemble all the parts as shown in circuit diagram.
- Transistor Q1 BC547 emitter pin is connected to Ground.
- Base pin is connected to emitter of Q2.
- Collector pin is connected to collector of Q2.
- Transistor Q2 BC547 emitter pin is connect to base of Q1.
- Base pi n is connected to Zener diode and resistor R2.
- Collector pin is connected to collector of Q1.
- 12V Relay one coil pin is connected to 12V supply.
- Other coil pin is connect to collector of Q1 and Q2.
- Capacitor C1 positive end connect to R2 and ZD1 junction.
- Negative connect to Ground.
- LED1 and R3 is connected as power indicator.
- Diode D1 and switch are connected from 12V power supply.
- Diode D2 and R1 are connected in parallel.
Conclusion:
Finally, this Fan Start 10 Second Delay Timer Circuit is very useful.
It is simple and effective and uses only transistors and basic components.
Also, delay time can be easily adjusted and therefore, beginners and students can build this circuit easily.
It is good for learning as well as real use.
References:
Timer delay to turn on and off a relay 10 seconds after power