Transcript:
[0m:06s] Hey, I’m Mitchell and welcome to another video in the RSP education series. These little suckers don’t care if your power goes out or if you unplug it. It remembers. Today we’re doing an autopsy on the latching relay, the industrial world’s most stubborn switch. Most relays need constant power to stay on, but this one only needs a pulse. Pulse it once and it stays on. Pulse it again and it turns off. The best part is it uses zero energy while holding its state. By the end of this video you’ll know why NASA uses these in satellites, how beginners wire them wrong, and the difference between memory relays and latching relays. If you like this content and want more educational videos, like and subscribe. This video is for educational purposes only. Consult a professional for your application. RSP Supply is not liable for any misuse of this information. Let’s dive right in.
[1m:03s] Latching relays, also known as bistable relays, differ from standard relays because they do not need constant power to maintain their state. They remember whether they are on or off even after power loss. This is why they are called bistable. They use two coils or polarity reversal to switch states and are ideal for energy saving applications. Most latching relays use a set coil to turn on and remain on, and a reset coil to turn off and remain off.
[1m:42s] A real world example would be a machine with a momentary button. Press once to start and press again to stop. A latching relay makes this possible without draining power. These relays require proper control logic such as a toggle circuit or two separate buttons, one for set and one for reset. Both memory relays and latching relays retain their state after power loss, but a latching relay specifically uses a momentary pulse to change states and requires separate signals to latch and unlatch.
[2m:33s] Latching relays are commonly used in energy saving applications where holding power is not ideal. Some benefits include zero power draw when idle, reliable operation during power loss, and suitability for internet of things, solar, and remote systems. The term memory relay is often used for any relay that remembers its last state after power loss. Memory relays may use mechanical latching, magnetic latching, or electronic memory in PLC or solid state relays. A key takeaway is that a latching relay is a type of memory relay, but not all memory relays are latching.
[3m:33s] Latching control logic is often used in ladder logic programming to keep a relay on even after the original signal is removed. This can be achieved using a seal in circuit or a two wire control method with separate on and off buttons. This allows machines to run without continuous input or power draw. In summary, latching means remembering the on or off state until instructed to change. When power interruptions are a concern, latching relays help ensure machines return online exactly as intended. For a full line of relays and hundreds of thousands of industrial automation products, visit rspupply.com.