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Relays

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Electromechanical relays and relay modules: 5, 12, 24 or 48 VDC coils, contacts from 5 to 30 A, in PCB-mount, slim panel-mount for cabinets, or ready-to-wire versions for Arduino.

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75 results

75 results

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Choosing the right relay

A relay is a controlled switch: a low-voltage coil closes or opens contacts that drive a separate circuit, often 230 VAC. Three pieces of information are enough to choose the right model.

  • Coil voltage: it must match your control supply. The Songle SRD-SL-C series comes in 5, 9, 12 and 24 VDC, and you can also find 48 VDC (TE Connectivity RT2, Zettler AZ692) or 230 VAC (TE Schrack RT424730).
  • Contact type: Form A / SPST-NO, a single normally-open contact (Hongfa HF46F, Sanyou SFK); Form C or 1RT, with normally-closed and normally-open contacts (Omron G5Q, Songle SRD-SL-C); 2 contacts (Omron G2RL, Phoenix 2RL) or 4PDT (Zettler AZ421, V23154) to switch several lines at once.
  • Contact current: 5 to 10 A for lighting and small loads, 20 to 30 A (Songle SRA, Sanyou SLI) for motors and heating elements. Allow a margin, since inrush current largely exceeds rated current.
  • Mounting: pins for PCB mounting, slim relay on a socket in a cabinet or PLC (Omron G5NB, Panasonic ALDP), or a wired module.

For a microcontroller, 1, 2 or 6-channel optocoupler relay modules already include the transistor and flyback diode. The HW-010 NE555 timer module adds an adjustable delay. See also other components.

Frequently asked questions

What is the difference between a bare relay and a relay module?

A bare relay is soldered or plugged in and requires a driving stage (transistor, flyback diode, resistor). The module includes this stage, often with an optocoupler, and connects directly to an Arduino or ESP32 output.

How do I know whether to choose 5VDC, 12VDC or 24VDC?

This is the coil voltage, meaning the voltage of your control circuit, not the load. The same 250VAC 10A relay often comes in 5, 12 and 24 VDC: choose the one matching your power supply.

What do Form A, Form C and 1RT mean?

Form A (SPST-NO) has only one normally-open contact, closed when the coil is energized. Form C, also called 1RT or SPDT, has a common terminal with a normally-closed contact and a normally-open contact, allowing switching between two circuits.

Is a 10A relay enough for a pump or a motor?

Not always: a motor draws several times its rated current at startup, and the inductive load wears the contacts. For this type of use, go for 20 or 30 A relays, or add a contactor downstream.

Why do two relays of the same rating not have the same price?

The price depends on the brand and series, the stated electrical endurance, the number of contacts, and the format (PCB mount, slim for cabinets, or ready-to-wire module).