Is a self-locking relay the same thing as a latching relay?

Question

This self-locking/inching WiFi relay can be configured to work in self-lock mode, in either NO or NC mode.

I’m not sure if self-locking means the same thing as latching. Wikipedia says:

A latching relay maintains either contact position indefinitely without power applied to the coil. The advantage is that one coil consumes power only for an instant while the relay is being switched, and the relay contacts retain this setting across a power outage.

The device above has a SRD-05VDC-SL-C 5V Relay component, and I saw a video where someone took one apart and it appears to have a copper coil which leads me to beleive this is using an electromagnetic current to close/open the contacts.

What happens if the coil is charged and then power is removed from the relay? Wouldn’t the contacts drop? If so, then how could the relay maintain the current state?

BTW this relay specifically states it is latching and uses the same component, so maybe my understanding of how the SRD-05VDC-SL-C 5V works is incorrect.

in the `-SL-` part of the part name the `S` means sealed and the `L` mean low power — Jasen Слава Україні, Nov 08 '18 at 08:27

Transistor · Accepted Answer · 2018-11-07T22:22:39.803

5

According to Mozar Tips YouTube video the relay is not latching.

According to the Amazon link the unit is HiLetgo 5V 1 Channel Latching Relay Module with Touch Bistable Switch MCU Control. It's not the relay that is latching - it is the module.

Figure 1. The board sports an STC 15F104E MCU. That's what's doing the latching.

Any device using the SRD-05VDC-SL-C relay will open its NO contact when the power is removed.

A latching relay is shown below.

Figure 2. Go to HomoFaciens and click "Start animation" to see how the pawl mechanism is advanced on every impulse of the relay coil.

edited Nov 07 '18 at 22:22

answered Nov 07 '18 at 22:16

Transistor

168,990
12
186
385

Wow, that’s really clever! Is there such a thing as a purely digital relay? – WhiskerBiscuit Nov 07 '18 at 23:55
Both of those relays are 'digital' as they can have only two states: 0 / 1 or on / off. If you mean 'solid state' then yes, 'solid-state relays'. – Transistor Nov 08 '18 at 07:04
that image is actually a ratchet relay, latching relays use different signals to turn on/off (either different wires or different polarity) – Jasen Слава Україні Nov 08 '18 at 08:15
True. And the ratchet one is worse in the sense that you have to keep track of the state somehow. Thanks. – Transistor Nov 08 '18 at 08:28

Is a self-locking relay the same thing as a latching relay?

1 Answers1