latching relays
- Thread starter Tom-D
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Assuming electronics, it is a relay that keeps it's position after the actuating switch has been released. The relay switch stays open or closed without further energizing of the relay coil.
Latching relays can be a couple of different things. A latching relay can be a normal relay that is wired into a circuit to latch something else electrically. In this case the relay latches itself on in the logic circuit and requires another device to break the latching circuit to drop it out.
Another form if latching relay trips a mechanical trigger that changes state of the output contacts and requires either mechanical or electrical reset to clear.
Another form of latching relay is a set/reset relay. The set coil operates the relay mechanism which is likely magnetically held in the energized position. The reset coil negates the hold in magnetism and drops out the rely to its deenergized state.
There may be other types.
Another form if latching relay trips a mechanical trigger that changes state of the output contacts and requires either mechanical or electrical reset to clear.
Another form of latching relay is a set/reset relay. The set coil operates the relay mechanism which is likely magnetically held in the energized position. The reset coil negates the hold in magnetism and drops out the rely to its deenergized state.
There may be other types.
I am not sure about that. There are relays that change state every time the input is pulsed. I call them flip-flop relays and I see them mostly on generator set day tank controls. They work alot like mini automatic transfer switches. Electrically operated, mechanically held.
These relays have 2 microswitches that flip when operated. If the common of one of them is wired into the pilot coil, then the operator is directed to another circuit to reverse the switch. On day tanks that would be the pump on and pump off floats.
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Capt. Geoffrey Thorpe
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The light switch on the wall is "latching", the doorbell button at your front door is not.
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I always thought a latching relay needed a certain condition to exist before it activated. Example would be a car will not start in gear.
PaulS
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A traditional latching relay is made so it holds it's position without being powered. You can design a circuit that will latch a traditional relay, but it needs to be powered. I'm talking mechanical relays here, basically dinosaur technology.
I just reread this question. You could wire the relay coil in series with a diode and it would pick up with current in one direction and drop out when the current is reversed. Is that what you want? I'd add a flyback diode to the coil to dissipate the drop out energy.
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From an old online Leach Relay Handbook, I believe Leach has since been acquired by Esterline and who knows after that.
5. What is a latch relay, and where is it used?
Latch relays are usually 2-coil, 2-position relays. The coil activation of one coil will transfer the armature and contacts to the other position. Conversely, activation of the other coil will transfer the armature and contacts back to its original position.The purpose of a latching relay is to conserve energy by pulsing the coil with a short pulse and removing the power once the relay has transferred.The latch relay lends itself easily to space applications because of minimal power drain on batteries.
5. What is a latch relay, and where is it used?
Latch relays are usually 2-coil, 2-position relays. The coil activation of one coil will transfer the armature and contacts to the other position. Conversely, activation of the other coil will transfer the armature and contacts back to its original position.The purpose of a latching relay is to conserve energy by pulsing the coil with a short pulse and removing the power once the relay has transferred.The latch relay lends itself easily to space applications because of minimal power drain on batteries.