Type of relay for this kill switch

mwdf

Member
2010-10-24 6:39 pm
Hi folks,

I'm new to the forum. It's been quite a few years since I did anything with car electronics or car audio, so I've forgotten just about everything I used to know!

While not strictly a car audio question, what brought me to this forum is a wiring question on relays.

I'm trying to wire in a "kill switch" for a radar detector, and I'd like it to function as follows:

- Radar detector is "always on" (wired to ignition switch).

- When I want to "kill" the radar detector, I push the "adjust driver side mirror" button.

- Radar detector remains "killed" until I push a 2nd hidden button under the dash.

Note: The radar detector should never reset itself. i.e. if I turn off the ignition and turn it back on, or push the kill button multiple times, it should still remain OFF. The ONLY way to turn the radar detector back on is to use the (momentary) reset switch under the dash.

Presumably the "adjust driver side mirror" button would need to be turned off as well, but that's not an issue. It's a rarely used button and is only turned on when adjusting the mirror (or to kill the radar detector).

Is a DPDT relay what I'm looking for? Or some kind of latching relay?

Thanks!
 

mwdf

Member
2010-10-24 6:39 pm
No Brian, no it's not. But I did see many threads on this forum that talked about relays and similar types of goals to mine, that did not even state what the purpose of the project was. For all people knew, they wanted to create a momentary switch that had a robotic barbie doll take her dress off - but since the posters never stated the purpose, somehow the questions got answered anyway.

If you like, I can edit my thread to remove the word "radar detector" so that it is a generic question just like the other threads I've read on this forum regarding relays, and then we can pretend it's for car audio.

The members of this forum are welcome to ignore my question, and I promise I won't be sad or have my feelings hurt. I promise I will have questions related to car audio at some point, but right now this is the project I'm working on.
 
Use a latching relay for the simplest solution. Sure you could rig up something with logic gates or whatever, but the latching relay will 'remember' its state over a power failure too. There are two basic types (as far as control goes). One has a single pair of leads for the coil, you switch the relay by controlling the polarity. The other kind has two sets of leads, one to switch one way, the other set to switch the other way. That's the kind you want. Connect the kill switch to one coil, connect the reset switch to the other. Hit reset, it stays on until you hit kill. Hit kill, it stays off until you hit reset. Simple. I'd mount the relay sideways so that a bumpy road is less likely to bounce the relay into the other position, though that is probably overkill. Don't forget about the protection diodes across the coils.
Try searching digi-key for "relay latching dual coil 12vdc"
 
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