What is it / What is it called?

[mkaake]

This is along the more basic line of questioning...

Basically, I'm wondering if there's an electronic component (or electromechanical, more likely) that can fill my need. I'm looking for something along the lines of a relay, but one that after being switched on/off, will remain in that state without power applied.

I'm building a small switching device, but would love to hold power consumption to a minimum by applying power to make the switch, and then disconnecting power after the switch has been made... while holding the specific switch in its commanded position (on/off).

Probably a pretty simple question, but the EE's in training I talked to recently weren't sure if there was anything quite like that available or not... so maybe someone with a bit more hands-on experience could pitch in a hand?

 

[kchriste]

You are looking for a set reset relay also called a latching relay. This is a relay with two coils; pulsing one turns it on and pulsing the other turns it off. It will remember it's state indefinately without power applied to either coil.

 

[Roff]

Sounds like you need a latching relay.

 

[gramo]

or this;

**broken link removed**

 

[mkaake]

thanks guys, I appreciate it -

 

[Roff]

or this;

**broken link removed**

I don't see how a SSR can work with power removed.

 

[awright]

A slightly different form of latching relay that is handy for some applications is a "Magnetic Latching Relay." Instead of having two separate relays on a common frame that mechanically latch each other, holding the position determined by the last coil energized, the Magnetic Latching Relay holds the position determined by the POLARITY of the last applied pulse. Magnetically latched relays also generally (but not always) have two coils so they can be switched by either the coil activated or the polarity of the activating pulse.

Another form of relay handy for some applications is the Alternating Relay that alternates between two states for each identical pulse applied.

awright

 

[HiTech]

Speaking of relays, boy those SSRs are darn expensive! I was going through the normal Bosch automotive relays like crazy from the exposure to weather and road salt. Tired from them corroding internally, (even after I applied silicone caulk and electrical tape to keep out moisture) I went the route of a solid state relay and everything is working fine to this day. The connections are greased with silicone paste to displace moisture. Fortunately I came across the SSR for free and saved a bunch of money!

**broken link removed**

 

[awright]

HiTech, do I understand correctly that you are using the relay illustrated in your post for an automotive application? Interesting. I thought SSRs for AC loads used SCRs or Triacs for the power switch, which makes me wonder how you commutate the relay to the off state in a DC application.

The only automotive application I can think of that would commutate the SSR off would be the windshield wiper that interrupts the current momentarily at the end of each stroke.

On the other hand, perhaps I am wrong about what is inside the SSRs. What are you using them for?

awright

 

[philba]

certainly not the ssr shown in the picture (it says AC clearly).

there are DC SSRs that use MOS or Bipolar drivers though I wonder how bullet proof they are. I'd definitely want to use kickback diodes with them.

 

[HiTech]

Yes, as philba points out about my representative photo--- it was the first Google image that popped up and I merely used that image, not that exact device. The SSR I am using is to switch on 12vdc to illuminate aux. lamps automatically when the vehicle is in reverse.

 

[zevon8]

Just as a sidebar, most common Silicone caulking ( RTV silicone ) uses acetic acid for curing ( what smells like vineagar ). Acetic acid is the grim reaper to copper and most other common electrical materials. Slowly but surely it will completely corode away those relays inside. The Bosch 332 series comes in a 'sealed' variety, and Tyco VF4 series as well as others makes the same units with weather sealed connectors. I use hundreds of them at work, never had a salt water intrusion failure.

Around electronics we use a Dow Corning silicone that cures via moisture/humidty, it is safe on electronics and bare metal.