Topic: RELAY'S (Read 2432 times)

wolf · « **on:** September 25, 2008, 02:13:18 pm »

We have them on some newer Bikes as well as your car. here is how to test them.

A relay is nothing more than an electronic switch. Completing a circuit through a coil in the relay causes a reaction that in turn causes a connection between two or more terminals in the relay. In some relays, breaking the connection to the coil causes a connection between two or more different terminals on the same relay. Technical stuff aside, the following will describe how to use a standard Bosch 4 or 5 pin 12 volt relay to accomplish some things you couldn't do (or couldn't do as easily) without a relay.

Here is a basic "Bosch" relay and circuit diagram. These relays are about 1" square, are generally black plastic and sometimes have a mounting tab on them. They are all numbered identically with the exception of pin 87A. Some do not have pin 87A. These relays cost no extra to have that pin so don't worry about that part. If you don't need that pin, you simply do not use it. See the schematics below to determine if your circuit will require that pin for your application.

* Pins 85 and 86 are your control inputs. This is where the magic happens. Applying 12 volts to one side and ground to the other will cause the coil to energize and the relay to activate (actually, these relays will activate with as little as 8 volts, but that's another story for a much more detailed discussion). Polarity is not important here and you can put your switch either in the power side or the ground side, depending on what you're doing. Generally though, you usually apply power to pin 85 and ground to pin 86, but this is not really important (you can reverse the polarity on these 2 pins without any problems, just remember to point your diode band to whichever side has the positive lead going to it. The coil creates a magnetic field which turns back on itself when power is removed, creating a power surge of little current but very high voltage. This can damage electronic devices in the circuit if left without this added safety device).
* Pin 30 is usually your high current input, either directly from the battery (fused, of course) or from an ignition or accessory circuit output from your ignition switch (also fused). In some cases, pin 30 is used for output instead of input, but we won't discuss that here since it doesn't apply to basic wiring.
* Pin 87 is for 12 volt power to the device you want powered up when the relay is activated by the coil being energized (when you press the horn button, for example).
* Pin 87A is only used if you need power to flow through the contacts when the relay is NOT powered up (such as a starter kill in an alarm harness) or if you are diverting power from one place to another by activating the coil (for example, if you are using the relay as a headlight dimmer switch). This is explained in the schematics below. Note that in the following diagrams, a fuse is not shown, but a fuse is always needed. The main input (usually going to pin 30) must be fused with the proper sized fuse for the accessory being connected. This is not an option.

wolf · « **Reply #1 on:** September 25, 2008, 02:29:08 pm »

A little more on them.

Relays serve several purposes. We will explain a few of those purposes, but these are nowhere near all of the reasons to use a relay.

1. Relays can be used to invert a switched input. Basically what this means is if you need something to have power that has a positive input but your switch provides a negative output, you need a relay. A basic example of this is a horn in most cars and trucks. Most vehicles use a ground output to activate a horn, yet most horns are physically grounded to the body or chassis, making a ground switched input useless. This is where a relay comes in. Using this example and the diagram above, we will create a basic wiring schematic to power up your accessory device. For those not familiar with schematics, this symbol represents chassis ground:
Schematic Ground Symbol
In this diagram, our switch is connected on the "ground" or negative side. Grounding the switch will create a positive 12 Volt output at pin 87.

Relays are used to send full power to a particular device while allowing a switch for that device to run significantly smaller wiring. This works extremely well for motorcycles where small wires can be run inside handlebars or other tubing yet can still be used to control high power devices like headlights, for example. In this diagram, our switch is connected on the "hot" or positive side. The wire to the switch and from the switch to the relay can be much thinner than the power wires. *Note that you can connect the switch input and the power for the relay to the same point, after the proper size fuse, of course.

Relays can also be used to divert power from one device to another using the same input wire. These can use either of the above type of switched input. We will use a motorcycle headlight circuit as our example. Using your manual, determine which wires in the handlebar housings control the headlight dimmer switch (most states require headlights on a motorcycle to be on at all times so we will use that as a guide, if you do not want your headlight on at all times while the bike is running (or when the ignition key is on), you may alter this diagram for that purpose. If you need help, feel free to ask, a link is provided at the top and bottom of this page for that purpose). In this diagram, pin 87A is used for low beam power (on when the relay is not powered up by the dimmer switch). 87 is used for high beam. (on when the relay is powered up). Run a new 14 gauge wire (fused, of course. A 10 or 15 amp fuse should be fine, dpending on the pwer requirements of your headlight.) from the headlight output of the ignition switch to the headlight bucket and connect that to pin 30 on the relay inside the bucket, making sure all exposed contacts are taped or insulated against shorting out (DO NOT CONNECT TO THE BATTERY or your headlight will stay on constantly, even when the key is off). If possible, mount the relay solidly (either rivet or screw it to the headlight bucket or use a wire tie (or tie strap) to connect it as solidly as possible). If not, insulate it against vibration and possible short circuits with foam rubber. Connect the dimmer switch input (the wire coming from the ignition switch to the handlebar switch) as if the switch were being used normally (if wiring from scratch, this can go to the same place as the wire going to pin 30, but can be much smaller than 14 gauge (18 or 20 gauge is fine for this purpose). The high beam output from the switch will go to pin 85 of the relay instead of to the headlight's high beam lug. The low beam output from the handlebar switch is unused in this case. Cut it back and tape it off to prevent a short circuit (it will still have power when the low beams are on. You can use this as an additional output for fog lights or other running lights that will shut off when the high beams are switched on, but you must use an additional relay for those).

Yep that's all folks

LA_Dave · « **Reply #2 on:** September 27, 2008, 01:27:23 pm »

Who needs a relay?

LOL

wolf · « **Reply #3 on:** September 27, 2008, 01:38:10 pm »

Anyone that does not want to carry a fire extinguisher LMFAO

LA_Dave · « **Reply #4 on:** September 27, 2008, 02:00:14 pm »

Quote from: wolf on September 27, 2008, 01:38:10 pm

Anyone that does not want to carry a fire extinguisher LMFAO

LOL...Over two years now and I haven't had any issues with it.

For the last year its been the only way I've started the bike...

wolf · « **Reply #5 on:** September 27, 2008, 02:09:55 pm »

Good deal Brother if it works hang in there with it. Reminds me of the old foot pedals on the older cars and trucks that did the same thing. One thing for sure you don't need to carry fuses.

LA_Dave · « **Reply #6 on:** September 28, 2008, 12:49:06 pm »

To be completely honest, I had an issue with the start button on my old controls. This was a "back-up" system I put together using a feeler-gage (.050") out of a blade pack. Never used the .050" anyway. Already had a hole in it. When my relay took a dump, bein' the cheap bastard that I am, I just started using this as the main start button...

Kind of a bitch to start if its in gear...LOL

sgaines · « **Reply #7 on:** September 28, 2008, 04:40:10 pm »

good information wolf although on my last build no relays but hardly no wires either

wolf · « **Reply #8 on:** September 28, 2008, 05:53:57 pm »

They are not used by a lot of Bike Builders, but most all cars have them now and it is good to know how to test them. Could save someone a Towing Fee as well as a Shop Charge.

sgaines · « **Reply #9 on:** October 02, 2008, 12:44:40 am »

i do agree........... got what little harness i have fused to battery with one 2 amp fuse so i don`t have a meltdown

Dave · « **Reply #10 on:** October 03, 2008, 03:15:51 am »

the solenoid set up ladave uses is earlier model.. a must have for early electric start models.. most relays are used on later model evo. type starter set ups where a remote button is used.. alot of us use the starter mount buttons now.. it does away with it all.. except the oldies they need the set up like la dave pictured to use an electric starter.. all in all.. most new bikes have them & it never hurts to know what they do exactly. the trick dave did with the feeler guage was always a favorite of mine.. you could even put the rubber boot on & it still works..

xylene61 · « **Reply #11 on:** October 09, 2008, 12:19:59 am »

LA Dave, do ya jam a stick in the spokes for a kill switch?

Dave · « **Reply #12 on:** October 10, 2008, 02:06:17 am »

actually thats the way it is on those type solenoids. a piece of heavy feeler guage is the equivilent to the lil' buttons you buy to put on the end of the late model starters to by pass other buttons & relays.. i used some cards on bicycle spokes when i was a kid.. matter of fact we did use a stick to slow us down on our bicycles ..

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Author Topic: RELAY'S (Read 2432 times)

wolf

RELAY'S

wolf

Re: RELAY'S

LA_Dave

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wolf

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LA_Dave

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wolf

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LA_Dave

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sgaines

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wolf

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sgaines

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Dave

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xylene61

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Dave

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