Relays, what are they and when are they needed?

[jonsamson]

I have recently installed running lights. I didn't want them to come on when I changed to high or when the key is turned on until the starter is hit. I wired one of the wires off the wire that goes direclty to the head light and another to the extra ground in the housing. I works as I wanted it to. But am I asking for trouble eventually?

I assume relays can be bought at Radio Shack, but how do we know what to buy for the application?

Can a relay be changed when changing blinkers to LED's without buying the extra electronics that draw as much as regular bulb thus defeating the purpose of the the lower draws for LED's

What is the basic's of how these little things work?

Why is the sky blue?

Why is it still cold that we can't ride comfortabley,

Opps sorry, got carried away with questions, I was on a role and didn't want to stop. :)

Thanks,
-Jon

[oldbikers]

I am sure that others will jump in and explain it a lot better than I can but a relay is added so that your running lights will pull 12 volts straight from the battery and not through the bikes small wiring to prevent burning up the wiring.

drawing by Cactusjack need to add a fuse in main 12 volt wire

[caddman11]

I'd buy from an auto parts store. Driving lights along with air horns can draw some serious current and the small wiring that's in the headlight bucket or under the tank is just not large enough to handle the current draw. LED's don't draw much current, whole different animal.

See drawing above---The relay acts as a trigger (use line 86) and when the relay see low current there, it completes the current so your accessories can be run basically direct from the battery (lines 30 & 87). You can use anything you want for the trigger, ignition switch, running lights, high or low beam, etc.

Right now I have two on my bike, one to fire my Stebiel horn and one to handle my driving lights.

[radco]

Like stated it breaks up te load.The switchs are light duty on the bikes,, so the extra draw will shorten their life,,, Auto zone has relays and you can make your own harness or buy 1 from Kuryakyn for 26$ all wired to the relay,, and color coded.. you just connect the dots...I have this one.. nice and neat,,,
http://store.valueaccessories.net/un...arylights.aspx

[ells]

Jon,

If you have 35W driving lights and the stock headlamp, you are probably going to be okay but you are close to the fused limit for that circuit. Using a relay as described above would give you some breathing room and the option to go to higher wattage bulbs.

[rlfaubion]

Originally Posted by Ells

Jon,

If you have 35W driving lights and the stock headlamp, you are probably going to be okay but you are close to the fused limit for that circuit. Using a relay as described above would give you some breathing room and the option to go to higher wattage bulbs.

+1 - Ells nailed it right on.... 35W running lights max without a relay.

[Top Cat]

Originally Posted by radco

Like stated it breaks up te load.The switchs are light duty on the bikes,, so the extra draw will shorten their life,,, Auto zone has relays and you can make your own harness or buy 1 from Kuryakyn for 26$ all wired to the relay,, and color coded.. you just connect the dots...I have this one.. nice and neat,,,
http://store.valueaccessories.net/un...arylights.aspx

Rich, I went to your link, when you say color coded you don't mean Color coded to each individual bike correct?
I mean Green to Green on the Nomad or red to red etc.

[cactusjack]

A relay is simply a remote-controlled switch.

The advantage to using a relay is you can use a low-current power source to operate a higher-current circuit. In motorcycles, the accessory and lighting wiring is usually very small gauge and is designed to handle only the power requirements of the basic motorcycle. Once you start adding devices that require a large amount of current, such as high-powered horns, driving lights, amplifiers, etc., the load these devices draw is way too much for the existing circuits.

So how do I safely power these devices on my Nomad, CJ?

Again, thinking of a relay as a switch - how does a switch work? It opens and closes contacts to either allow or prevent electricity from passing through it. A standard 30 or 40 amp automotive grade relay has 4 or 5 terminals, numbered 30, 85, 86, 87 (5 terminal relays have an 87a. Terminal 30 is connected to the battery using a large gauge (10/12ga) fused wire. Terminal 87 is connected to the (+) terminal or connector on the device you wish to power.

When the contacts close, +12v flows from the battery through the relay to the device. Unlike a toggle switch, there is no manual lever or button to control the flow. There is an internal coil that is operated by a second power source which does the work. Terminal 86 can be connected to an external switch to provide manual control, or it can be connected to a switched +12v circuit that is powered on/off by the ignition switch. So if you wanted your device to be on whenever the ignition is on, like the taillight, this is how you do it. The coil requires very little current to operate, so it can be safely connected to the existing wiring. If you want to have the device powered on with the key, but still want to have manual control, you simply add a switch between terminal 30 and it's power source. Terminal 85 is connected to either ground or the (-) battery post.

By using a relay, you are protecting your electrical wiring and components from the effects of high-current devices.

Edit: it just occurred to me I didn't mention the difference between terminals 87 and 87a on a 5-terminal relay. 87 is for a normally open circuit (the switch contacts are normally open until the desired
event happens to close them) This is the one you will almost always use. 87a is just the opposite, a normally-closed circuit. Sorry for leaving it out of my explanation.

[jonsamson]

Thanks guys, great explaination everyone and the details CJ.

So I have 2 - 55 watt running lights, with both wires spliced off in side my bucket and one on the same relay for the head light the other to ground. And a 15amp fuse at the fuse panel for the head light and the running lights. I don't have a separate switch nor do I want one. Umm, seems I am asking for trouble eventually of a complete light failure and most likely it will be at 2 am on a Saturday leaving a pool hall.

I have a project for Saturday.

What I want to do is have the head lights off and the running lights off when the ignition is turned on. After I hit the starter both the running lights and the head lights come on. I understand than One wire 10/12 would run from the battery + to #30 on the relay. The Negative to #85 relay. The wire to turn on the lights to terminal #87.

What wire would I connect to #86 so the running lights stayed off until I hit the starter? ??? (Diagram is a big help Oldbikers, thanks I am very visual learner)
-Jon

[rlfaubion]

CJ, I'm not a critic by any means, but I found your dissertation of "how it works", as right informative and a good read.

I just wanted to add to the definition of "close", as in close the circuit, which is what you're discussing, and what it really means.

The first and hardest part I had to understand about circuits wat that "close" was not close as in close out a current or stop it. "Close" is actually open, as open the flow - Well if you think like me anyway.....

So "closing" a circuit is to keep it "open" or flowing....

Like if you had current running through your garage door opening, but when you opened the door the current was broken or stopped and only until you "close" the door will you have the continuity.... whew.... I hope this helps novices like me....

Thanks CJ

[radco]

Originally Posted by Top Cat (TC)

Rich, I went to your link, when you say color coded you don't mean Color coded to each individual bike correct?
I mean Green to Green on the Nomad or red to red etc.

when I said color code, i ment coded for lights,power, switch...not to each bike,,, the set up is nice and clean,, and the relay is already wired in,,, you just hook your trigger wirer up to where ever, the hot to the battery, and 1 wire to each light,, (white wire if I remember right...Thats what I like,, hard to make a mistake,SIMPLE like me :)... I mounted the relay in the headlight bucket,, stays nice and dry and no condesation,like you get sometime in the side covers,,, .....Rich

[bobhamlin]

Originally Posted by Valdez (lone Juan)

The first and hardest part I had to understand about circuits wat that "close" was not close as in close out a current or stop it. "Close" is actually open, as open the flow - Well if you think like me anyway.....

You're not the only one who has trouble matching a visual with the term. Why is it called a "relay" in the first place? My visual of a relay is something that hands an object off to something else.

This device is an electric drawbridge, an electric set of heavy duty jumpers, -- something along those lines.

[watchman]

Hook #86 to your low beam headlight wire. The lights will only work with the low beam headlight and they will not come on until the engine is started.

[Cajunrider]

I've never had electricians at the plant explain relays as good as you guys just did. I need to print these out and use them in training guides. Thanks.

[cactusjack]

Originally Posted by watchman

Hook #86 to your low beam headlight wire. The lights will only work with the low beam headlight and they will not come on until the engine is started.

Maybe you can help me understand why you would always want your driving lights on with the low beam only, or why you wouldn't want them on with the high beam (which is how I ride during daylight hours)?

I would suggest using the running lights wire as the relay trigger (to terminal #86) and placing a switch inline to permit manual control of the driving lights. There may be times when you don't want them on.