Best/easiest way to do the following:

[GCAdidas13 10+ year member]

So you have something like this...

A KnuKoncepts distro with the volt meter, and it has a ground wire that needs grounded to read voltage.

A 15" green neon tube for glowage, has + and - 12v.

A four-prong relay.

Now, What is the best or easiest way to have the neon and the distro volt meter come on only when the amps are on?

Thanks,

Brian

P.s.: those of you that say hook the relay up so that the trigger is the amp turn-on lead and the swich is the neon/volt meter's grounds... it doesn't work. the relay will only allow a positive charge through the switch.

Click to read more...

 

[Pete 10+ year member]

So... grounding everything normally and then putting a relay inline with the positive 12v for all the devices doesn't work?

To do it properly you need to have a constant 12v wire (preferable coming off the battery through a fuse) and a 12v remote wire coming from your HU.

Terminal 85 = Ground

Terminal 86 = Remote trigger from HU

Terminal 30 = 12v feed from battery

Terminal 87 = the 12v inputs for the DVM and Light

Terminal 87a = No Connection

That should work.

Terminal numbers are assuming you are using a standard SPDT relay where terms 85 and 86 are the coil and 30 (common), 87 (N/O), and 87a (N/C) are the contacts.

I am a little confused as to your comment about the light needing +12v and -12v... -12v does not exist in a car. If you are reading the light connections correctly you have a 12vAC light that you are trying to put into a 12vDC car... If that is the case let me know and I can still help out, but it is going to be alot more involved.

 

[GCAdidas13 10+ year member]

So... grounding everything normally and then putting a relay inline with the positive 12v for all the devices doesn't work?

Well, I would do that, but the volt meter that I have is hardwired directly into the fuse (see http://knukonceptz.com/productDetail.cfm?prodID=FB-1024D)

I am a little confused as to your comment about the light needing +12v and -12v... -12v does not exist in a car.

How stupid of me, I meant just +12v and ground. Basically it was a cigarrette lighter plug, and I cut the plug off.

So basically, I have just the grounds to work with. I tried to kill two birds with one relay, but a relay needs a positive charge across the 30/87 terminals. When I put a negative (ground) charge across them, it didn't close the switch, it opened it. (Information aquired at http://www.bcae1.com/relays.htm)

Thank you very much,

Brian

 

[Pete 10+ year member]

So... did you get it working?

If not try this:

Terminal 85 = Ground

Terminal 86 = Remote trigger from HU

Terminal 30 = Ground

Terminal 87 = The ground connections to the light and DVM, but not for the amps.

Terminal 87a = No Connection

This will cut the ground when the remote trigger is not energized and complete the circuit when it is energized.

You are a little confused with how relays work.

When there is NOT a complete circuit through the coil (85 and 86) then 30 is directly connected to terminal 87a.

When there IS a complete circuit through the coil then 30 is directly connected to terminal 87.

It makes no difference what is connected to terminal 30 at all as far as how the relay will react. This is why relays are so useful for so many different things and why they are so flexible.

If for some reason it all isn't working after you try this method, then let me know and give me specifics on how the equipment is hooked up.

Pete

 

[JimJ 5,000+ posts]

-12v does not exist in a car

in his car.

//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[Pete 10+ year member]

and I suppose you're running a 400v plate voltage to the cathodes in your amps front end just to sweet up the sound?

Adding a high B+ will really clear up the sound too //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[JimJ 5,000+ posts]

nah, i'm all solid-state in the van //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

for now //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif but actually, i half-said that jokingly, there are 12V positive ground systems in vehicles, but they're pretty rare.

 

[Pete 10+ year member]

I have heard of a few trucks from around the 50's or 60's where the chassis was energized with 12v and ground was carried through the wiring. So I guess anything is possible.