How to wire in an electrical device using a relay.

[stinkwheel]

This is assuming the electronic device you want to run:
1) Is to be turned on and off with the ignition.
2) Runs on battery voltage.
3) Doesn't draw so much power it overloads your motorcycle.
4) Is being attached to a motorcycle with a 12v, negative earth system. ie pretty much any Japanese road bikes over 125cc made after 1980.

So something like heated grips, a GPS or a cigarette lighter socket for an airbed pump or a mobile phone recharger.

This method of attaching devices has a few advantages:
1) It does not interfere with any of the other systems on the bike. If this device fails, it will not make anything else fail along with it.
2) The fuse and wiring are appropriate to the current load of the device.
3) It is neat and tidy. In electronics, a neat and tidy solution is almost always the correct one.
4) It can be set up to allow for other devices to be attached in future.
5) Your device will turn off when the bike is turned off preventing the battery from being run flat if you forget to turn it off manually.

This is not the only way of doing the job, it is certainly not the quickest or easiest way, but it is the best way.

Choosing your components

First a small amount of maths. You need to work out how much power draw to allow for which will determine what thickness of wire you use and what size fuse to fit.

You normally need to know the current draw in Amps. Some devices give this, more often they give the power consumption in Watts on a label on the back and you have to work it out. Luckily it's simple. Current (Amps) = Power (Watts) divided by Voltage (Volts).

So say I wanted to attach a device that draws 40 Watts. 40W / 12V = 3.34 Amps. So that is the absolute minimum I need to allow for.

CABLE

In reality. Cable usually comes in thickness's suitable for 3, 8, 17, 23 and 35 Amps. So in this case I'd want to go for 8 Amp cable. However, using heavier cable than needed is often a good idea, it is less likely to melt or catch fire if overloaded.

There is also the choice of colour. Try to be logical, it helps with fault finding later. Different manufacturers will use different colours to represent a particular function. In my example, a Honda, they use red for wires that are live all the time, black (with or without tracer colours) for wires that are live only when the ignition is on and green wires for earth. As such, I have bought black, green and red wires. (On a Kawasaki, a black and white wire would be an earth so choose accordingly.)
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/DSCN0628.png
FUSE

There will also be a fuse. This will blow, cutting the power if the current drawn by the circuit exceeds the fuses rating. It should be slightly higher than the current draw of the device but lower than the rating of the cable. This means it won't blow during normal usage but will blow before the cable is damaged. Fuses usually come in 1, 5, 10, 15, 20, 25 and 30A ratings. In this case I'd want a 5A fuse.

I have chosen to use a "mini blade" type fuse and holder in this case. This is because replacement fuses are commonly available at fuel stations.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/DSCN0590.png

All of that said. In the actual example I'm using, I have fitted 17A cable for a device that draws just over 3A. This is because I may want to use the same wiring for additional devices in future. 17A cable should allow me to run pretty much anything I want, doesn't cost much more than 8A cable and is no harder to fit. I have chosen to fit a 5A fuse for the time being.

RELAY
Simple. I am using a 4 terminal, normally open automotive relay. They cost around £2.50.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/DSCN0594.png

CONNECTORS
You have two main choices. Either non-insulated crimp connectors or pre-insulated crimp connectors.

I personally prefer the non-insulated connectors for a variety of reasons but they are not as commonly available. In either case, it is imperative that you use the correct crimping tool for the connector type and apply TWO crimps per connector. One trapping the bared ends of the wires, the other trapping and sealing the insulation.

I have used spade connectors to attach to the relay because this is all that will fit. I've used bullet connectors elsewhere because I find them less prone to coming loose. It would be perfectly fine to use spade connectors throughout.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/terminals.png
Pliers are NOT a suitable substitute for crimps.

The "scotchblock" tap connectors or "Chocolate block" screw in connectors are NOT suitable for motorcycle wiring. Use them at your peril, they WILL fail and cause intermittent electrical faults.

To my disgust, the device I was fitting came with a tap connector and instructions to use it to tap into the headlamp wiring. All this will lead to is both your device and the headlights intermittently turning on and off in about 18 months time.

Choosing where to fit your relay

You need to find three wiring points on your bike:
1) Battery live: This could be either the battery positive itself or where the battery positive connects to the starter solenoid.

2) Frame Earth: This could be anywhere there is a bit of exposed, bare metal on the main frame or engine with a bolt attaching to it or the battery negative itself. Look for somewhere the manufacturer choose as a frame earth as being a good bet.

3) A switched live: Any wire which is only live when the ignition is switched on. The wires supplying power to either of the brake light switches or the flasher relay are a good bet as they are also non-essential.

You will also need somewhere reasonably protected where you can fit your relay.

On most bikes the bulk of the wiring is behind one of the side panels or under the saddle. On the CB500 I'm using, all the required parts are within a few inches of one another behind the right hand side panel along with enough space to attach a relay below the starter solenoid.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/DSCN0586.png
I drilled a small hole in the plastic storage box that forms the back of this area to attach the relay to with a nut and bolt once it's all connected up. It's easiest to leave it unattached until it's all connected up.
Relay attached to storage box below the solenoid.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/DSCN0596.png

Fitting the wires

FIRST DISCONNECT YOUR BATTERY Negative first, then positive.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/DSCN0589.png


Getting the wiring neat takes a bit of practice. I'd suggest attaching one end of the wire and running it along the desired route to the relay then cutting it off a bit long. Once all the wires are in place, wrap them up together with PVC tape, cut them to length and attach the other connectors.

This is what you need connected to your relay
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/relay.png

BATTERY LIVE
This is the wire that will be carrying the power from the battery to your device. It will also incorporate the fuse.

In this case the fuse holder comes with enough red wire attached to run from my chosen attachment (the solenoid) to the relay. So a ring terminal on one end to attach to the solenoid and a female spade connector on the other end to attach to the relay at terminal number 30.

I'm checking which of the two terminals is the battery live before I disconnected the battery. The reading was positive so the one with the red probe is the live. If it was negative, the one with the black probe would be the live
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/DSCN0588.png
Wire and fuse holder attached using a ring terminal.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/DSCN0592.png

EARTH
Mr Honda chose to attach his frame earths under the left hand side panel, on the reg/rec mounting bolt. Who am I to argue?

I've attached a green wire to the same point with a ring terminal. I've looped the wire across to the right side following the existing wiring route and attached a piggy-back spade connector to the other end. This is because I want to use this earth wire to earth both the relay and my device. This connector attaches to terminal 86 on the relay.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/DSCN0606.png

SWITCHED LIVE
I've chosen to use the power supply to the rear brake switch.

Unfortunately, it attaches using a connector block. I've had to cut the wire either side of the connector block. I left the other wire (that takes power from the brake light switch to the bulb) in the connector block for simplicity.

To the "bike" end of the wire, I've attached a TWIN female bullet connector. To the "switch" end of the wire I've attached a male bullet connector and plugged it in, restoring normal brake light function.

You will notice the wire landed up too short to connect so I had to splice in an extra bit of wire to the end of the switch. To do this I used a double butt crimp connector then applied shrinktube over the top of it.

I also attached a male bullet connector to a piece of black wire and plugged it into the twin connector. I attached the other end of this to terminal 85 of the relay.

"Switch" side of connector block
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/DSCN0598.png

"Bike" side of connector block
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/DSCN0599.png

Male bullet attached to switch (note shrinktubes splice)
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/DSCN0602.png

Twin female bullet attached to bike
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/DSCN0601.png

Brake switch reattached, Relay connector also attached via twin connector
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/DSCN0603.png


DEVICE CONNECTORS
Now we need the two wires that supply power to your device. I've chosen to run the earth wire right back to the main frame earth. You could substitute a shorter earth wire to a frame earth nearer the device.

Now I'm fitting this to a faired bike. I've decided I want the power supply to run to the right side of the fairing, I'll attach my device to its power supply here and in the future, I may fit a power socket inside the storage compartment that is located here.

On an unfaired bike, you may prefer to run the wires into the back of the headlamp shell. Take care to protect the wires from rubbing or pulling when the handlbars are turned.

Anyway, there are already wires in the loom that run up to this point so I'll follow the same route with mine.

I've attached a female spade connector to a green wire (denoting an earth) and attached it to the earth wire I put in previously using the piggy back connector.

I've attached a female spade connector to a black wire (denoting a switched live) and attached it to terminal 87 of the relay.

I wrapped both wires together in PVC tape and followed the route of the existing loom under the tank, and out along the front subframe. Attaching it with cable ties as appropriate.

I put a twin female bullet connector on the other end ready to attach one or more devices to.

Wires all connected into the relay (note piggy-back connector on the green wire
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/DSCN0604.png

Wrapping the wires in PVC tape makes them less prone to damage and pulling out. As well as looking neater
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/DSCN0605.png

The finished article. Relay bolted in place, wires wrapped. Looks like it came like that from the factory? Good. It's supposed to.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/DSCN0607.png

The wires routed alongside the main loom (yellow dashed line) which should avoid them becoming trapped, rubbed or melted.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/DSCN0609.png

Finally lands up with two, twin bullet connectors energing at the front right part of the fairing, ready to attach whatever device I want.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/DSCN0610.png

Testing your circuit

Reattach your battery.

When you switch the ignition on, you should hear a *click* from the relay as it switches on. When you turn the ignition off, it should *click* again.

Now attach a voltmeter or bulb where you'd attach your device. You should have a voltage (bulb glows) ONLY when the ignition is switched on.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/DSCN0624.png

Make sure the brake light (or whatever you used for your switched live) works as normal.

You're done. It's a good job and you've done it properly. Treat yourself to a cup of tea and a cigarette.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[instigator]

Superb Post.

[stinkwheel]

I used this wiring to fit some Symtec heated grips. HOW I FITTED THEM
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[supZ]

nice work there m8y

i did a similar thing but built myself a little 'box of tricks' to handle it.

mini fuse box with 10amp fuses and a standard automotive relay. one side of the contacts are soldered together with wire going between them to create a 1 to 4 way live (or 8 using piggy back connectors)

https://farm5.static.flickr.com/4066/4356929556_3edba7a3e8.jpg

https://farm5.static.flickr.com/4043/4356930596_1f7ed8d66b.jpg

it now sits strapped onto my bike (well, its in the tool box tray at the moment but i've had to remove my puncture repair kit so i'll probably move it and strap it to the inside of the subframe)

anything new i install just needs one end to the frame/earth and a spade connector on the other side to plug into my accessory box

fink, one of the guys on bikersoracle (cbr600) makes his own plug and play harness that works in the same way for about a tenner.. VERY handy to have something like this if you're connecting devices to your bike
____________________
CBR954RR - Daily toy
CBR600RR - Trackbike

[chris-red]

You can tell this is no SRAD kneedragger post, look at those hands!
____________________
Well, you know what they say. If you want to save the world, you have to push a few old ladies down the stairs.
Skudd:- Perhaps she just thinks you are a window licker and is being nice just in case she becomes another Jill Dando.
WANTED:- Fujinon (Fuji) M42 (Screw on) lenses, let me know if you have anything.

[smegballs]

Nice post, is there such a thing as an AC relay? For use on batteryless off-roaders and the like.

[Tim..]

A very helpful and informative post

[stinkwheel]

[Pete.]

Good post Stinky!
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Fortuna]

Good thread dude.
Can I make a suggestion?

[stinkwheel]

[tahrey]

Bookmarked for GREAT JUSTICE. I followed this guide (mostly) and everything went just peachy.

In the absence of Fortuna saying anything, I'll just add that fuses are actually available in an even more bewildering variety at halfords & the like; so you can actually get a fair bit closer to the rating you need but must also be sure of what size & type you're after...

EG thanks to 'frauds typically rubbish stock-level-maintenance, in order to replace some that I blew I had to get a multi pack ... in which there's a 2A, 3A, 4A, 5A and 7.5A; and just in the common or garden blade-fuse range there's "normal", maxi, mini and micro sizes (most bits of my bike and car take the mini ones, but the high rated "main" fuses - and wierdly the one for my hotgrips - are full size).

At least it's fairly easy to tell which is which even if the writing's worn off - my heated grips came with a 4A one, which under the ineffable colour-coding scheme these things have, is a rather christmassy kind of violet... just match the colours.

A new thing they seem to have, which is probably more useful in a car's crowded fusebox, are LED-lit ones. IE when the thing blows, the power is diverted through a little light so you can see which one it was straight away. Though the 4A one I installed had it (unavoidable - they were the only ones still on the shelf) I'm not particularly keen on the idea to be honest - you have to have the ignition on whilst looking, it trivialises the whole process of what should be a serious "why's this electrical item gone badly enough wrong to blow the fuse?", and... well... *current must still be flowing* in order to light the LED. Even if it's got a pretty heavyweight resistor in-line with it (and it must to drop 12-14v down to a usable level for LEDs), this doesn't strike me as the safest plan ever...

[Raffles]

[Fortuna]

[el_oso]

can a mod please put this in the guides section?
needed to double check what relay pins went where and took me a while to find this
____________________
Duke 390
Previous: '05 XR125L | '96 XJ600S Diversion |'05 Suzuki GSXR1000 | '05 Honda CBR125-R | '97 YZF 600R Thundercat | '11 Honda CBR250
Car: Jeep Wrangler 4.0L

[stinkwheel]

Holy Necro thread.

Just wired up Mrs stinkwheels new bike for accessories. It's a CBR600 FV.

A few refinements this time and I'm very pleased with the result.

I've used a small relay/fuse holder block this time. This cost about £3 from vehicle wiring products. Also the usual 4 pin, normally open relay.

https://lh3.googleusercontent.com/3VBll04SsgVqlODnrLQbQEapamkkMeP28tZcWbGdPShmR6DggMYYHSxW5l3oxok1UHpRXz4gBueGbIdtSme4YmIIbdyeDeRlJuAg92FUw25wlNtYTZDsMsNuYYEl-elHjrB0jilgzg=w1125-h874-no

I took the wires direct from the battery terminals up to the relay housing, attached to the battery with ring terminals. So live into terminal 30, earth into terminal 86. Switched live terminal 85 and output terminal 87.

I spliced into the switched live to the rear brake switch (the white terminal block at the bottom right of the picture) with a soldered splice. This is the only place I've cut into the bikes wiring and I made sure to do it on the switch side of the terminal block so the main loom hasn't been tampered with.

I "daisy chained" the output from terminal 87 into one side of each of the three fuse holders.

I then got a piece of 5 core wire. (Really only needed 4 cores but I had a spare bit). I attached one core to the earth. Another three cores were attached to the other side of the fuse holder.

Stuck the holder to the inside of the mudguard using a piece of VHB adhesive pad. Then ran the 5 core cable alongside the main loom up to the handlebars.

I now have three, relay controlled and seperately fused accessory sockets plus a common earth return at the front of the bike. I'll be putting heated grips on one. A heated vest on the other and there's a spare.

If you buy a bit too much 5 core cable, you can split the remaining bit to give you various coloured bits of wire to work with making the other connections.

My fusebox is the bottom left one.

https://lh3.googleusercontent.com/xj9Ro_TfcvN71wplnaW9NjkcFBHJsrork2pDc03UkvLo-wkcmy-YDxjbsWxbJvpxOmaJgkSCw5hfDUDaXiULNw0HWjFk4iqNYRvBklR3R8xMWfplNGdUbqlv39hiuLNBXUZM5B_xxQ=w1164-h873-no
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Haydl3]

Hey stinky

I’ve put a 5a in line fuse from the battery to the relay do I still need one on the usb accessory

[stinkwheel]