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Looking for a particular relay for a project and don't know what the actual trade name or descriptive words it is called. Must be 12 volt of course. Most relays have 2 outputs to power 2 lights or accessories when activated. I need a relay that will alternately power the outputs when activated. One output would always be powering a lite or accessory and triggering the relay would send the output power out the other output connector to a different lite or accessory.
Knowing the real name of this relay would make it easier to find /inquire about. I do know they are available somewhere and would like to acquire one if possible. Thanks in advance for the multitude of replies and questions about my project. If it works, the nite riders out there will likely love it.
 

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One output would always be powering a lite or accessory and triggering the relay would send the output power out the other output connector
Does that mean the first is off when the second is on and vice-versa? If so, an automotive Bosch relay might be what you're looking for.
 

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You can probably pick up what you need at a Radio Shack. Relays come in two general variations; normally open and normally closed. A normally open relay breaks the circuit (opens the switch, however you want to look at it) when no voltage is applied and closes the circuit when voltage is applied. Conversely, a normally closed relay closes the circuit when no voltage is applied and opens it when voltage is applied.

They will typically have four connections. Two of them are the coil and two are the contacts. The load is connected to the contact connections and they act just exactly like a switch. The coil connections are connected in series with whatever you want to use to trip the relay. The coil is really an electromagnet and when energized it pulls a plate on the contactor to it. This can either make or break the circuit depending on the relay design (normally closed or normally open, respectively).

If you need to use two of them you can wire the coil connections in series. One side of one coil to whatever you trip the relays with, the other side of the same coil to one side of the coil of the second relay. The second coil connection of the second relay goes to ground. When you close the switch to trip the relay it will trip both of them. One can be normally open and one normally closed if desired.

The only catch is to insure that the contact rating (in amperes) is higher than the amp draw of your load. Amps can be calculated by dividing Watts by volts (for example when using relays with lights). If you have two 50 watt lamps at 12 volts, that is 100 total Watts divided by 12 volts yields a load of 8.33 amps. For a load like that I'd use a 15 or 30 amp relay. I like at least a 50% safety factor so 15 would handle everything fine.

If you really want to be safe you could also wire a fuse in series with the load. Again, just make sure the fuse rating is slightly above the load and lower than the contact rating of your relays. For the example 8.33 amp load I'd probably use a 10 amp fuse and 15 amp contacts in the relay or a 15 amp fuse and 30 amp contacts on the relay.
 

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Discussion Starter #5
Thank you, looks like I want an alternating relay but will investigate all the choices so I know what is out there for the capturing in the future.
 

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You need a Bosch 5 pin relay. It has 2 outputs, one is normally closed and it switches to the other one when powered. They are usually rated at 30amps, which is usually enough to power two lights. When you go to find it just say you need a "Bosch 5 pin relay".
 

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spongebob218's reply made me realize that I forgot to mention that there are also double-throw relays where one side of the contacts is normally open and the other side is normally closed.

You can also get double-pole (or triple-pole) relays that have multiple "circuits" (or channels or paths) in them. These are good if you want to wire two completely separate circuits with one relay.
 

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Not sure if this is the same as what you are trying to do but take a look at this link...
http://www.canyonchasers.net/shop/generic/relay.php

I did this little project last week, hooking up my com system and gps and it works great! 8)
I couldn't find the "distribution block" he talks about and it's the one thing he doesn't have a pic of, so I used two "distribution bridges" from radio shack (one side of each).
 

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I found some stuff that might work for you:





The first is a 5 pin relay (Ford Part# FOAZ-14N089-A $7.38)

Sorry for the photo quality,

Pin 30 - Switched power
Pin 87a - First load
Pin 87 - Second load
Pin 86 - Ground
Pin 85 - Trigger

The second picture is the pigtail the relay plugs into but it's kind of high (Ford Part# 3u2z-14s411-asaa $33.37). You can probably get one at a junk yard cheaper. There's more than one on every Ford made over the last 15 years.

Hope this helps.

kevin
 

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Discussion Starter #10
Vstromper

That could be a good solution to my project without high cost. I will check the auto wreckers here and cross my fingers. Thanks everyone for the ideas and info.
 
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