Friday, December 5, 2025

Electronic Toggle/Ratchet Relay

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An electronic toggle ratchet relay is a specialised type of relay that, unlike standard relays, maintains its state (either on or off) even after the control signal is removed. It ‘latches’ into position and changes state only when it receives another trigger pulse. This makes it incredibly useful for applications where you need a momentary input to result in a persistent action. So, it is used for converting momentary inputs to on/off operations.

A standard relay would only stay on while the button is pressed. An electronic toggle ratchet relay, however, would turn on with one press and stay on, then turn off with the next press. It converts momentary inputs into latched outputs, activated via the onboard push-button, an external switch, or an appropriate trigger.

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A true ratchet relay (see Fig. 1) operates with a single pulse input and relies on magnetic memory to retain its switched state.

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Ratchet relay
Fig. 1: Ratchet relay

Refer to the datasheet for more details. However, this system employs an unconventional design and can be best described as an electronic toggle or ratchet relay system.

In this configuration, the load is controlled using a push-button switch. When a switching threshold is detected at the input terminal, the relay toggles and latches into its new state. Upon receiving the next trigger signal, the relay toggles again, functioning like a flip-flop.

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The functional block diagram of the proposed design is shown in Fig. 2.

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T.K. Hareendran
T.K. Hareendran
Hareendran Nair TK is a lifelong electronics enthusiast, educator, and innovator whose journey from curious child to seasoned expert reflects an enduring passion for technology. With decades of hands-on experience, he has witnessed—and actively contributed to—the evolution of electronics from vacuum tubes to modern microchips.

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