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Dual Power Socket for Honda CB500s

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engi57

New Member
Hello,

This is my first post on this forum so if anything needs changing just let me know. I am looking to install a Dual Cigarette style power socket on my Honda CB500s. I have had it fitted and working on there before, directly powered from the battery, but I am looking for a neater/safer solution with a fuse holder, power indication light etc. I have drawn a very basic schematic to illustrate what I am aiming to achieve. I have a couple of questions regarding my diagram;

- How many watts are provided through a motorcycle "hot" wire? I know that W=VxI but I don't know the amperage either!

- Are all "hot" wires equal to each other? do they all carry the same voltage/amperage? Just so I know if I can tap into any supply on the wiring loom.

- Since vehicle wiring (on most motorcycles) is designed in a way that assumes electrons flow from positive to negative, is my schematic possible? Or do I need to run my components the other way round? Surely if a fuse holder was the first thing after the positive feed it would negate the effect of having one in the first place because it would be the last thing to be reached by a surge?

I have included a picture of my schematic (apologies for amateur drawings) and a schematic of my bikes wiring loom. I know that I will probably need higher than a 1/2 watt resistor for the LED but as I don't know how to calculate the amps going through the live wires I'm not sure which one to use. I have linked the "BBcode" to the image since this is what is recommended by imgur for forums, so please let me know if you can't see them. Feel free to offer any suggestions and I will appreciate any help/advice.

Thanks.

VRAI7jr.jpg [/IMG] yq3XwV3.jpg [/IMG]
 
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KeepItSimpleStupid

Well-Known Member
Most Helpful Member
A fuse really protects the wiring. It's a controlled point where the element melts and doesn't cause damage.
Automobile cigarette lighters are either wired to be on all the time or on with the ignition. You may want both.
Typical ratings are around 15 Amps.

So, you can use a fuse per socket and wire direct to the battery to get the most amount of power on all the time. Alternatively, there should be power routed from the ACC section of the ignition switch that supplies power when in the ACC position. There is another bus that supplies power to the ignition circuits only. At least based on car wiring. In a car, the ACC bus is disconnected while the car is actually trying to start. This has the effect of say, turning your heater/radio off, but not the lights.

You could supply the cigarette lighter via a relay, like the automotive BOSCH style if your doing high loads and wish to have it on when in the accessory position.

In my opinion, your best to use a DIN socket rather than a lighter plug. See http://www.amazon.com/BikeMaster-European-Cigarette-Lighter-Adapter/dp/B003A3GUEO for an example.

Here: http://jhau.maliwi.de/misc/fs.en.html is a Combo Plug. This usually has an internal fuse. This is what I would recommend to put on your devices, Use an adapter to the US cigarette light if you have to and cannot change the end. That might happen with some GPS's.

I'll point you to this document: http://www.google.com/url?sa=t&rct=...=MgvlO7Z7UXxqTNV_oK2RpQ&bvm=bv.59568121,d.cWc

The biggest problem I have had is that a lot of the cigarette plugs fit poorly in a lot of sockets. In a motorcycle, they would likely fall out. The combo plugs allow the US type of cigarette lighter and the DIN power plug of European origin to be used.
 

heydonms

Member
- How many watts are provided through a motorcycle "hot" wire? I know that W=VxI but I don't know the amperage either!
Current is a function of resistance and voltage so, for a fixed V, I varies depending on what is plugged in. When you are building something that supplies power the wattage specified is the maximum rating not a fixed value that it always supplies.

- Are all "hot" wires equal to each other? do they all carry the same voltage/amperage? Just so I know if I can tap into any supply on the wiring loom.
As a general rule all power wires will be at 12V (there will be some special ones that you don't want to mess with, anything related to the ECU, sensor, ignition, etc. but being a bike it is more likely to be carby than EFI and you probably don't have too many of those sorts of things to worry about). Not all wires have the same current rating, pull 10amps from your instrument cluster lighting wire and things will melt. Thick wires can carry more current than thin, if in doubt run a heavy wire from your alternator/battery and use a relay.

- Since vehicle wiring (on most motorcycles) is designed in a way that assumes electrons flow from positive to negative, is my schematic possible? Or do I need to run my components the other way round? Surely if a fuse holder was the first thing after the positive feed it would negate the effect of having one in the first place because it would be the last thing to be reached by a surge?
Electrons always flow from negative to positive. Current can be thought of as either a flow of negative or positive charge (and in fact in some cases it is a flow of positive charge). Current flowing from +ve to -ve is called conventional current and it works exactly the same as electron flow, the only time it matters which one you use is when you are doing maths and even then you only have to be consistent. Both are equally correct and as long as you don't try to work with both at the same time you are fine.

The current flowing in a circuit is the same at every point in that circuit at any given time, it doesn't flow through one lightbulb, then the next, then the fuse, it flows through everything at once. This might be easier if you stop thinking of electricity as a flow of electrons, think of it as a field which forms between two things of different potential allowing them to equalise. The field forms instantaneously when the conductors are connected along the entire length of the circuit and in that moment charged particles throughout the circuit begin moving to equalise the charge. It isn't electrons leaving one end of the battery and flying through the circuit to the other end, it is electrons (or plasma or ions or any mobile charge carrier) from everywhere moving due to the influence of the electric field. In fact individual electrons typically move at a speed of several cm/minute so the electrons leaving the -ve end of the battery could easily take many minutes to reach the +ve side.

The fuse should be located close to the +ve of the battery because the rest of the bike is connected to the -ve. Imagine the insulation on a wire is damaged and it touches part of the bike, if the wire is connected to -ve then nothing happens because the two things are at the same potential, now imagine the wire is connected to +ve, you have just created a short and you want a fuse in the circuit. You can't put a fuse between the bike and the -ve so you have to put a fuse between the +ve and every wire that will carry a voltage.

I have included a picture of my schematic (apologies for amateur drawings) and a schematic of my bikes wiring loom. I know that I will probably need higher than a 1/2 watt resistor for the LED but as I don't know how to calculate the amps going through the live wires I'm not sure which one to use.
I can't see the images, but the important value is the current rating of the LED. Find what current the LED wants (I) and the voltage of your bike (V, if your bike is 12V then use V=15 or so, the charging voltage for a 12V lead acid battery is 13.8V and you will get the occasional surge), calculate the resistance using R=V/I (EDIT: this is wrong, see below) and the power using P=VI. I doubt you will need more than a 1/2W resistor if you are just trying to light up a status LED.
 
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heydonms

Member
Of course, sorry, my instructions for calculating the resistor value are wrong, you need to subtract the forward voltage drop of the LED from the supply voltage. Use the calculator thingy unless you are particularly interested in the details.
 

4pyros

Well-Known Member
Most Helpful Member
Are all "hot" wires equal to each other?
No it depends on the wire gage and what it is fused at as well what else it powers. Run your own fuse off the battery.
Since vehicle wiring (on most motorcycles) is designed in a way that assumes electrons flow from positive to negative, is my schematic possible? Or do I need to run my components the other way round? Surely if a fuse holder was the first thing after the positive feed it would negate the effect of having one in the first place because it would be the last thing to be reached by a surge?
Electrons flow from negative to positive.
The fuse is to protect the wire from over heating if there is a short.
 

heydonms

Member
Up the resistor to at least 680 Ohm and put the fuse on the +ve side and you should be all set.

Your schematics look much better than most of my hand drawn ones so I wouldn't apologize, the only minor point I would make is that LEDs have arrows coming off them, you have drawn a normal diode.
 
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