A relay is an electronic switch used to cause switching action of different components with an electrical signal as opposed to a mechanical actuation. These modules are either done purely electrically or electromechanically.

2. What are the types of relays

Relays are classified by operation principle: Electromagnetic (mechanical coil-driven, suitable for high currents), Solid-State (semiconductor-based, fast, long-lived but generates heat), Reed (sealed contacts, lower wear), Thermal (responds to temperature), Magnetic Latching (holds state without power), and Hybrid (combines EMR and SSR). Selection depends on required switching speed, current rating, lifespan, and application environment.

3. What ways can I use relays in a robotics project?

Relays can be used in places where mechanical switches are generally used. This enables you to implement wireless control over those switches and thereby make the whole project/product more sophisticated. Relays are also used in places where automations are used, mainly acted upon by a trigger.

4. What is a bad relay?

A bad relay would be a relay that may have been internally damaged. In electromechanical relays, sometimes the mechanical actuator can break or stop working due to build up of dust over time. In a solid state relay, the transistor that operates the relay could get damaged if the voltage supplied to the relay was much greater than what the relay was designed to handle.

5. What is a relay switch? Is it the same as a relay?

""Relay switch"" is a synonym for a relay. Both terms refer to the same device. Relays are electromagnetic switches that control high-power circuits using low-power control signals. Unlike manual switches requiring direct hand operation, relays enable remote, automated switching and electrical isolation between control and load circuits. The term emphasizes that relays function as automated switches replacing manual mechanical switches.

6. Where can I buy relays online?

Relays can be obtained from almost all online stores including Robocraze. But specific types of relay may vary in availability.

7. Where can I buy relays at a shop near me?

Standard electromagnetic relays are widely available at local electronics shops, hardware stores, and authorized component distributors. Specialized relays (solid-state, magnetic latching, reed) may require visiting larger electronics retailers or ordering online. For convenience and selection, Robocraze stocks various relay types and modules with fast delivery across India. Check product compatibility before purchasing

8. What is the cost of relays in India?

Relays can vary in cost substantially depending on the manufacturer, rating, extra features like circuit protection, material used, etc.

9. Can relay modules be used with Arduino or Raspberry Pi?

Yes, they’re a perfect match for both. A relay module acts as a bridge between low-voltage microcontroller control (like Arduino or Raspberry Pi) and higher-power circuits. You wire the module’s control input to a GPIO or digital pin on the board, power the module (commonly 5 V), and then you can turn devices on/off safely via the relay contacts. Because many modules support standard logic levels and include driver circuitry, hooking up to Arduino or Pi is straightforward.

10. How many channels do these relay modules have?

It varies quite a bit, you’ll find modules with single channels (one relay), dual-channel (two relays), four channels, eight channels and more. For example, a “4-Channel 5 V Relay Board Module” offers four separate relays in one unit. The number of channels essentially tells you how many independent electrical circuits you can control from one module.

11. Are these relays suitable for AC appliances?

Yes, many relay modules are designed to switch AC loads, making them suitable for controlling lights, fans, heaters or other AC-powered appliances. When used appropriately, they let your microcontroller board control mains-level devices. That said, you must check the module’s relay contact ratings (voltage and current) to ensure your appliance is within safe limits, and always follow proper wiring and safety precautions.

12. Do the modules include protection circuits for safe operation?

Many relay modules come with additional circuitry designed for safer interfacing: opto-isolation (to separate the low-voltage control side from the high-voltage load side), flyback diodes or snubber circuits across relay coils, and separate power inputs for the relay coils vs logic side. These features help prevent damage to your microcontroller or wiring from coil spikes or interference when the relay switches. Attention to these protection elements makes the modules more robust for embedded and DIY use.

Relay Switches

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Specifications Chart (Voltage, Channels, Load Current)

Module Type	Control Voltage	Number of Channels	Max Load Current	Common Use
Single-Channel 5 V Relay Module	5 V DC	1	10 A @ 250 V AC or 30 V DC	Controlling a light or motor from Arduino
2-Channel 12 V Relay Module	12 V DC	2	10 A each	Dual appliance control, robotics
4-Channel 5 V Opto-Isolated Module	5 V DC	4	10 A each	Home automation panels, multiple loads
Solid State Relay (AC type)	3–32 V DC control	1	40 A+ @ 250 V AC	Heavy industrial load switching

Applications: Home Automation, Robotics, IoT

Home Automation: Turn lights, fans, or heaters ON/OFF remotely or via sensor triggers.

Robotics: Use relays to handle high-current motors, solenoids or actuators that microcontroller cannot drive directly.

IoT Systems: Sensor detects event → microcontroller triggers a relay → device switches accordingly (e.g., water pump, door lock).

Smart Systems: Multiple channel relay modules allow control of many loads via a single microcontroller board for building smart control panels

Mechanical Relays vs Solid-State Relays (SSR) – Comparison

Feature	Mechanical Relay (EMR)	Solid-State Relay (SSR)
Moving parts	Yes – physical contacts move	No – uses semiconductors
Switching speed	Slower (ms)	Very fast (µs – ms)
Wear & lifespan	Contacts wear out after many cycles	Very high cycle life (no contacts)
Noise	Audible click when switching	Silent operation
EMI & arcing	Might spark when switching heavy loads	Minimal sparking, cleaner switching
Load types & cost	Good for inductive loads, lower initial cost	Better for fast switching; needs cooling, higher cost

Feature

Mechanical Relay (EMR)

Solid-State Relay (SSR)

Moving parts

Yes – physical contacts move

No – uses semiconductors

Switching speed

Slower (ms)

Very fast (µs – ms)

Wear & lifespan

Contacts wear out after many cycles

Very high cycle life (no contacts)

Noise

Audible click when switching

Silent operation

EMI & arcing

Might spark when switching heavy loads

Minimal sparking, cleaner switching

Load types & cost

Good for inductive loads, lower initial cost

Better for fast switching; needs cooling, higher cost

Safety Tips for Switching High-Voltage Devices

Always disconnect power before wiring the load side of a relay (especially mains AC).

Use proper insulation and secure enclosure for terminals carrying mains voltage.

Ensure the relay’s voltage and current ratings exceed the actual load.

For inductive loads (motors, solenoids), add flyback diodes or snubbers to protect the relay.

When a relay switches mains AC, maintain safe distances and use proper rated cables.

Mount the relay on a non-conductive board, keep wiring tidy and avoid loose connections.

Use a fuse or circuit breaker on the high-voltage side for added safety.

Ventilate SSRs: although silent, they can generate heat and may need heatsinks in high load use.

Item Name	Price Inc. GST (As of 30th Sep. 2022)
12V Relay Cube	12
6V Relay Cube	14
5V Relay Cube	17
9V Relay Cube	45
12V 8-Channel Relay board	310
5V 1 Channel made in INDIA - GL Make	36
JQX-15F(T90) Coil Voltage DC 24V 6 Pin Power Relay	54
24V Relay Cube (Pack of 2)	53
5V 30A 1-Channel Relay Module	181
Waveshare Modbus RTU 8-channel Relay Module RS485	2599
12V 30A T90 Relay	47
5 Pin 48V DC Coil Voltage Electromagnetic Power Relay	79
Multifunction Delay Relay Switch Module	474
DC 6V To 30V One Way Relay Module	279
16 Channel 12V Relay Module Board	593
12 V 1 Channel Relay Board Module	53
5V 1 Channel SSR Module	146
NE555 Pulse Frequency Duty Cycle Adjustable Module	77
5V 8 Channel SSR Module	958
5V 2 Channel SSR Module	378
SLA 12VDC 4Pin 30A Power Relay	65
SLA 5V DC 4Pin 30A Power Relay	49
4 Channel Relay Wireless Module	731
FOTEK Solid State Relay SSR-25DA 25A	317
NE555 5V Delay Timer	67
5V 16 Channel Relay Module	625
Single CHANNEL 12V RELAY MODULE 30AMP	162
Four CHANNEL 12V ULN2003 BASED RELAY BOARD MODULE	247
12 V 1 Channel Relay Board	47
12V 4CH Relay Board	209
12V 2CH Relay Board	80
4 Channel Solid State Relay	552
FOTEK 24V-380V 40Amp DA Solid State Relay Module	408
Time Delay Relay Module (0-10 seconds)	60
8 Channel 5V Relay Board	247
4-Channel 5V Relay Board	130
2-Ch 5V relay Board	69
1CH 5v Optocoupler Relay Board	62
2 CH 12V Relay Board	135
1 CH 5V Relay Board	49
8-CH 12V ULN2003 Based Relay Board	424
4-CH 12V Relay Board	178
1-CH 12V Relay Board	60

Item Name

Price Inc. GST (As of 30th Sep. 2022)

12V 8-Channel Relay board

310

5V 1 Channel made in INDIA - GL Make

JQX-15F(T90) Coil Voltage DC 24V 6 Pin Power Relay

24V Relay Cube (Pack of 2)

5V 30A 1-Channel Relay Module