12V relay question

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Grand_Wag_85
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Joined: Sat Aug 27, 2011 8:46 am

12V relay question

Post by Grand_Wag_85 »

I'm trying to rig something with a pair of 12V relays and I'm a little stumped. I'm trying to set one of the relays up to be normally on and the other relay normally off. There is one trigger wire that will trigger the "normally off" relay and the goal is to have that relay trigger the other relay to shut off until the trigger voltage is cut. In a nutshell one relay will always be on depending on if there is a trigger signal.

I know I've seen a diagram for this online before but I can't seem to remember what they call it, let alone how to wire it up.
82 J10
77 J10 Golden Eagle 401
88 GW

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tgreese
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Re: 12V relay question

Post by tgreese »

If you use the usual Tyco/Bosch relays, each has a normally open (NO) and normally closed (NC) contact. Use which one you want. The coil always switches from the "normal" position to the "active" position when energized. If your relays do not have both NC and NO contacts, you've got the wrong part. You want a SPDT (single pole, double throw) relay.

I would not wire your relays in series (ie the first firing the coil of the second). Instead I'd use the right part, two SPDT relays with the coils in parallel, or one DPDT relay.

Lots on the internet about these parts: https://www.bing.com/search?q=Bosch%2FTyco+relays

Try PartsExpress - cheap there, and they have sockets that will make wiring much easier. https://www.parts-express.com/cat/12v-r ... ockets/399
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
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Grand_Wag_85
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Re: 12V relay question

Post by Grand_Wag_85 »

These are the relays I've got along with the sockets and pigtails

Image
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tgreese
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Re: 12V relay question

Post by tgreese »

No problem. 85 and 86 are the coil connections, not polar. 30 is the input, 87a is NC and 87 is NO. Confirm with your multimeter if needed. Usually the diagram shows the at rest state of the contacts, but this diagram is backwards - the coil pulls the contact toward it, so check that it's not showing you the energized state. Where are you getting 24 VDC to power the relays? This is not a proper relay to run on your Jeep.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.
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Grand_Wag_85
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Joined: Sat Aug 27, 2011 8:46 am

Re: 12V relay question

Post by Grand_Wag_85 »

Got it all figured out, you're the man Tim!

After checking with the multimeter I realized the only way to get it to work it by using 85 as the trigger(negative), 86&30 to positive, 87A for one load and 87 for the other. I'm glad I was able to eliminate one relay altogether! When I had it set up with a positive trigger both 87 and 87A had power.

Good eye on the voltage! This is for a CB base station and it's a safety mechanism for the AMP & preAMP so I don't accidentally key-up with the preAMP engaged.
82 J10
77 J10 Golden Eagle 401
88 GW

You know it's bad when your car is on the EPA's 10 most wanted list!
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