Using a relay to auto-power on HDD and power inverter

**Startingline13** · 02-21-2010, 09:51 AM

I'm sorry, by white or yellow I meant from the relay tails.
I found photos here:

http://www.cadvision.com/blanchas/54pontiac/relay.html

Specifically this part:

"Automotive relay pins are labelled with numbers which indicate what their purpose is and the relay pigtail has a standard color code as follow:

Coil

85: Ground - Black wire
86: +12V - White wire

NOTE: I found that in half of my pigtails, the black and white wires were reversed! It shouldn't make a difference as the coil is not polarized.

Contacts

30: Common - Blue wire
87: Normally Open (NO) - Yellow wire
87a: Normally Closed (NC) - Red wire"

I'm going to skip the switch for now and just concentrate on getting this to work correctly without it first, then I'll add the switch at some point in the near future. So if I have no switch, the blue tail does not get used, correct?

**Curiosity** · 02-21-2010, 10:27 AM

OK, let's see.
Black to ground is correct.
White to 12V switched source (ACC). That's the + side of the coil.

Blue is common.
Yellow is normally open. Those are the contacts that close when the coil is active.

87a/red wire. Don't need it. That's connected to blue only when the coil is inactive.

**Startingline13** · 02-21-2010, 10:38 AM

Gotcha. Red wire is no good.

I'll let you know how it goes in a few, thanks again for everything.

**Startingline13** · 02-21-2010, 11:16 AM

Ok, now I have the:

Black grounded
Yellow to IGN/ACC

and Red and Blue are taped off and tucked away.

All that's left is white. When I popped open the inverter, at the on/off toggle switch on the inverter there are two red wires, one to the top of the switch, another to the bottom. Does it matter which one of these the white is connected to?

**Curiosity** · 02-21-2010, 03:59 PM

Oh wow. I am not responsible for anything that happens.

**Startingline13** · 02-21-2010, 07:14 PM

Sorry didn't mean to sound like a noob there.

I wound up just taking the easy way out and wiring up a carnetix that I had lying around. That took care of the 5v I needed for the USB hub, and the 12v needed for the HDD.

I'm still stuck with that final part regarding the power inverter.

**Curiosity** · 02-21-2010, 07:44 PM

Well, spoonfeeding can only get you so far in life. That page you linked to explains the basic concept of relays. Read it and think about it. It's just a switch and electromagnetic coil.

**Startingline13** · 02-28-2010, 11:21 AM

I'm sorry if it came off that way but I wasn't trying to be spoon fed with everything.

At the moment my connection looks like this:

- yellow wire is connected to the IGN from my car.
-red wire is capped off
-blue wire is capped off
-black wire is grounded

This leaves me with only the white wire. When I opened up the power inverter, I found that if I touch both ends of the power on/off toggle switch on the inverter that I can turn the inverter on/off, but It does nothing when I turn the ignition off. The power will just remain on.

Obviously the wires are not tucked away or soldered at the moment, this was just to display for the forums.

What am I missing here?

**Startingline13** · 02-28-2010, 11:45 AM

photos for the previous post

**Curiosity** · 02-28-2010, 11:46 AM

When you touch the 2 wires on the switch together, it should turn the inverter on. That's basically what a switch does. It's connecting those 2 wires together.

Now understanding that, the yellow wire is wrong. Yellow (Common/30) and Blue (NO/87) are like a switch. So where do those go?

Black and White are connected to the coil. When the coil has current passing through it, it closes the switch. So where do those go?