hooking up relay?
Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=82287
Printed Date: July 06, 2025 at 5:05 AM
Topic: hooking up relay?
Posted By: oxygen65
Subject: hooking up relay?
Date Posted: August 30, 2006 at 10:23 PM
i read the section about relays on the 12 volt and i dont understand it really so i was wondering if somone could explain it to me a little better or draw me some kind of diagram. im trying to hook up video monitors in my car and i want to do 6 or 7 of them and everyone is telling me that i can not just run all of them off of the acc wire, and that i need to add a relay. well i dont understand how to hook it up. i think what eveeyone means by using the relay is that the acc wire is hooked up to one side of the relay and then a constant 12 volt is hooked up on the other side and when the acc wire gets power it lets the constant 12 volt wire go threw. i think that might be it but im not sure, anyways if someone could draw me a pic of how im suposed to do that i would really appriciate it. thanx
Replies:
Posted By: swamprat323
Date Posted: August 31, 2006 at 12:57 AM
im not sure how much power the moniters draws, may need 2 relays or a bigger relay. soem one here shold coem along and give soem info onhow much they draw.
but lets say 1 SPDT 30 amp realy can handel the job.
85 ground
86 form ACC
87 12 volt
30 to power the moniters
Posted By: mrjc480
Date Posted: August 31, 2006 at 3:07 AM
A common relay has (5) post. 87a is connected to 30 normally. When 85 and 86 receive 12+ and 12-, the pin pivots from 87a to 87 thus breaking the 87a/30 circuit and connecting 87/30. Connect 85 to gnd, 30 to your monitors, 87 to a fused wire directly to your battery, and 86 to your accessory wire. Be sure to cap off 87A cuz it will show 12+. When the key is turned to activate the accy wire, it will energize the relay, thus passing current from the battery to the monitors.
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Im moving to MEXICO and Im not speaking spanish!
Posted By: oxygen65
Date Posted: August 31, 2006 at 1:33 PM
when you say to make sure i cap off 87a becuse it will show 12+ what do you mean by that? do you mean just hook up a conecter onto it that has no wire?
Posted By: oxygen65
Date Posted: August 31, 2006 at 1:42 PM
another question i have is what size wire can a use to hook up 87? if i used something like a 10 or 8 ga wire will i blow the relay? becuse im tring to run 6 to 7 monitors off of that one relay. somone mentioned how much they draw. the only info i can come up with on that is they draw like 7 watts so i dont know how you can figure if a 30 amp relay is can handle all that, but i did find a 13 inch flip down tv and it said that power draw was like 3 amps. but anyways im just wondering what size wire i can run from my battery to 87 on the relay.
Posted By: oxygen65
Date Posted: August 31, 2006 at 1:47 PM
or would just buying relays with the relay sockets work best and do the same thing?
Posted By: bsd1
Date Posted: August 31, 2006 at 4:04 PM
oxygen65 wrote:
<FONT color=#0000cc size=2>when you say to make sure i cap off 87a becuse it will show 12+ what do you mean by that? do you mean just hook up a conecter onto it that has no wire?
pin87a connects to pin30 when your relay is idling. When it's idling, pin30 gets no 12V+, therefore, pin87a does not need to be cap off. Leave the 5 pin relay as is is fine.
For caution, yes, you can plug a connector and cover up pin87a since it's not in use. And you don't want pin87a to touch any metal in your car while the relay is energizing to cause a short.
Posted By: oxygen65
Date Posted: September 01, 2006 at 12:38 AM
what about the size of the wire i use to run 87 from my battery? what size should that be? or does it not really matter? becuse im using it to run 6 or 7 monitors.
Posted By: mrjc480
Date Posted: September 01, 2006 at 4:10 AM
Add up the amp draw of ALL monitors. If the total is less than 30 amps, then you can use one relay with a 30 amp fuse on a 16 ga or bigger wire. The easiest thing to do is to buy a video amplifier with built in power leads and relays.
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Im moving to MEXICO and Im not speaking spanish!
Posted By: oxygen65
Date Posted: September 01, 2006 at 2:03 PM
and were can i find a video amplifer like that becuse i have never seen one?
Posted By: mrjc480
Date Posted: September 01, 2006 at 3:52 PM
a custom shop should have them or check online. a popular brand is farienheit (or something). retail is probably $50. you will need a video amp regardless because of the number of monitors.
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Im moving to MEXICO and Im not speaking spanish!
Posted By: oxygen65
Date Posted: September 01, 2006 at 5:52 PM
i looked at farenhiet video amps and they dont have that do you know of any other companies that would make them? the closest thing i found was a phoenix gold tantrum DD5 and i can only find pictures i cant find anywere to buy it.
Posted By: oxygen65
Date Posted: September 01, 2006 at 6:00 PM
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