Imagine a smart switch for your appliances with a built in waiting time.
This 220V time delay switch circuit is like a fancy power button that waits a bit before turning on your lights, motor or other device.
You can set it to wait a few seconds or minutes after you turn it on.
The circuit uses a special switch called a triac to control the electricity.
So, you can use it for things like delaying the start of a heater to avoid overloading circuits or adding a dramatic pause to stage lights before a performance.
Circuit Working:
Parts List:
| Category | Component | Quantity | Notes |
|---|---|---|---|
| Resistors | 22k | 1 | |
| 1k | 1 | ||
| 220Ω | 1 | ||
| Capacitors | Electrolytic 1000µF 50V | 1 | |
| Electrolytic 470µF 50V | 1 | ||
| Electrolytic 100µF 50V | 1 | ||
| Semiconductors | SCR BT169 | 1 | |
| Triac BT136 | 1 | ||
| Diode 1N4007 | 1 |
This circuit for a time delay switch is designed to activate an AC load, such as lamps after a delay of three minutes.
It serves to protect the load from inrush current and power on transients, which can be harmful to the device.
The switch is directly connected to the AC lines to power its components.
Resistor R1 reduces the AC voltage and D1 rectifies it to provide low voltage DC.
The high value capacitor C1 acts as both a smoothing capacitor and the time delay element.
The SCR only conducts once C1 is fully charged which typically takes around 2 minutes.
When C1 is fully charged, the gate of the SCR receives a firing pulse, causing it to conduct.
This, in turn, charges C2 providing an additional minute to trigger the Triac through R3.
Once the Triac conducts, the AC load receives electrical continuity and turns on.
Capacitor C3 maintains the voltage level at the gate of the Triac eliminating any backlash effect.
It is important to exercise extreme caution when handling this circuit as it operates at mains lethal potential.
Do not touch any points when it is connected to mains power.
This circuit should only be constructed by an experienced person.
Formula:
An RC (Resistor Capacitor) timing circuit is commonly used to determine the time delay for an SCR circuit utilizing resistors and capacitors.
The resistor R and capacitor C values in the circuit determine the time delay (t).
The following is the fundamental formula for an RC circuits time delay:
t = R* C * 1.1
where:
- t is the time delay in seconds.
- R is the resistance in ohms Ω.
- C is the capacitance in farads F.
Important Notes:
Accurate timing is ensured and the charging and triggering features of the SCR are compensated for by the 1.1 factor in the calculation.
For your application, select resistors and capacitors with the right voltage and power ratings.
Because component tolerances might impact timing accuracy, test the circuit to make sure the actual time delay matches your computation.
Using an SCR and RC timing components, you can precisely design time delay circuits with this formula and method.
Depending on the particular needs of the application and the features of the component, adjustments might be required.
How to Build:
Below are the steps for building a Simple 220V Time Delay Switch Circuit with Triac:
Safety Precautions:
- Ensure you are working in a safe environment and all components are disconnected from power before starting.
Circuit Design:
- Refer to the schematic diagram provided earlier.
Component Placement:
- Place the components on the breadboard or PCB according to the schematic.
- Make sure to leave enough space between components to avoid short circuits.
Connect Power Supply:
- Connect the 220V AC power supply to the circuit.
- Ensure proper insulation and safety precautions are in place.
- Once the circuit is built test it by applying power.
- The Triac should switch on after the delay determined by R1, R2 and C1.
- Adjust these components to achieve the desired delay time.
Connect Load:
- Once the circuit is working correctly, connect the AC load e.g. lamp to the output of the triac.
Final Check:
- Double check all connections and ensure everything is properly insulated and secured.
Operation:
- Apply power to the circuit and observe the delay before the load turns on.
- Adjust the delay time if necessary.
Important Safety Notes:
- This circuit operates at 220V AC mains voltage which can be lethal.
- Exercise extreme caution and follow safety guidelines.
- Ensure all connections are secure and insulated to prevent electric shock or short circuits.
- If you are not experienced in working with high voltage circuits, seek assistance from someone who is or consult a professional electrician.
Conclusion:
A 220V time delay switch circuit with a triac can be built using common electronic components.
This circuit provides a delay in switching on an AC load, such as a lamp after power is applied.
Care should be taken when building and testing the circuit due to the high voltage involved.