Simple Solid State Relay (SSR) circuit is like ON/OFF switch but with more better and modern; not like normal switch with moving parts but this one uses special electronics parts like transistor or triac for turning ON or OFF.
Also, it works quietly with no noise and last a long time, it is very good for many electronic projects.
Circuit Working:
Parts List:
| Components | Values | Quantity |
|---|---|---|
| Resistors (All resistors are 1/4 watt) | 1k | 1 |
| 56Ω | 1 | |
| 39Ω | 1 | |
| 330Ω | 1 | |
| Capacitors | PPC 10nF 400V | 1 |
| Semiconductors | Triac TIC226 | 1 |
| Opto-coupler IC MOC3041 | 1 |
IC like MOC3040 or MOC3041 works same like normal opto coupler but does not use phototransistor, as they use phototriac which can handle 100 mA 400V at 25°C.
But Normal opto coupler with phototransistor is not always we can do this.N
One big good thing about this IC is, it work with many SCR and triac, hence, while making solid state relay (SSR) for 220V we need to pick right triac based on what load we are using.
For resistive load like bulb or heater TIC226D triac 400V is okay, but for inductive load like motor or fan it is better to use TIC226M 630V triac.
Also, capacitor C1 must have working voltage same or more than triac need.
For resistor R1 on input side we can find value using formula with input voltage Vin and LED current Ioc from MOC opto coupler.
Example:
If Vin is 12V and Ioc is 30mA standard for MOC3040 R1 = 356 ohm we can use 330 ohm which is close enough.
For MOC3041 with Ioc = 15mA R1 can be around 680 ohm.
This 220V SSR can handle up to 8 Amp and if we need more power then we need to use stronger triac.
Formula:
Understanding R1 Formula in Simple SSR Circuit
Formula:
R1 = 1000 × Ioc × (Vin – 1.3)
where:
- R1 is the resistor value on input side which is in ohms Ω
- Ioc is the current going through LED in optocoupler which is in mA
- Vin is the input voltage in volts V
- 1.3 is the voltage drop across LED in volts
Explanation:
In simple SSR (solid state relay) circuit using optocoupler we can use this formula to find R1 resistor value and this resistor stop too much current from going to LED.
How to Build:
To build a Simple Solid State Relay SSR Circuit we need to follow the below mentioned steps:
How to Make the Circuit:
- First, collect all parts same like in circuit diagram.
- Next, connect one side of load to 220V power supply and connect other side of load to MT1 pin of triac.
- Now MT2 pin of triac go to phase live wire of 220V AC.
- Then take positive input voltage and connect it to anode of MOC3041 LED using resistor R1 in series.
- After that, connect negative input to cathode of MOC3041 LED.
Testing the Circuit:
- Give input voltage to MOC3041 and check if load resistive or inductive turn ON and OFF when input voltage change, also it should work same like switch.
Safety Tips:
- Make sure all wires and parts are connected properly and that no wires are loose.
- Also, use safety items such as gloves and goggles while working and be careful, because this circuit uses a high voltage of about 220V, which can be dangerous.
Note:
- This is just a basic circuit and we can change or add more things if needed and always check component datasheet and use good practice when making circuit.
Conclusion:
A Simple Solid State Relay (SSR) circuit works as an electronic switch that uses solid-state components and it does not use any moving or mechanical parts inside.
Also, it gives many good things like strong working, long life and very fast switching, because of this it is good for many uses in industry machines and automation work.