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dual power socket for honda cb500s

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Member - Posts: 4
Member spacespace
Joined: January 19, 2014
Posted: January 21, 2014 at 3:03 PM / IP Logged  
This is my first post on this forum so if anything needs changing just let me know. Not sure if this forum is still active since there haven't been many recent posts. 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.
dual power socket for honda cb500s - Last Post -- posted image.[/IMG]
dual power socket for honda cb500s - Last Post -- posted image.[/IMG]
Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: January 21, 2014 at 6:22 PM / IP Logged  
For starters, put the fuse & switch on the hot (+12V) side. (Reasons include safety & to stop people pinching your battery power or shorting your battery to GND.)
2V LED from 12V @ 20mA... V=IR => R=V/I = 12/.02 = 600 => a 560 or 670 Ohm resistor. P=VI = 12 x .02 = .24W hence use a 1/2W resistor.
How many Watts? It is the load that determines that else its fuse else wire gauge - whichever is the lesser.
And hopefully the wire gauge is NOT the lesser - that's called a fire or explosion and new bike.
Electricity is NOT the flow if electrons. Forget all that crap and simply refer to the flow of conventional current which is +ve to -ve THU the circuit.
[ FYI - I'm dealing with that in another thread where writers are getting very confused over that same issue. They think a diode will not work because "it let's electrons thru the other way"...
BTW - electrons flow opposite to conventional aka "+ve" current - ie, electrons flow negative to positive thru the circuit (but +ve to -ve thru the supply, battery etc). Confused? Stick to +ve/conventional and + to - THRU THE CIRCUIT. ]
The fuse side has nothing to do with electricity flow direction. Fuses are placed on the "hot" side.
EG - on older +ve chassis/GND vehicles and in traditional telcos they are one the -ve side.    On modern -ve GND vehicles etc they are on the +ve side.
Fuses should NEVER be placed on the GND side of any circuit (unless you know it is the only possible GND path during a fault).
As to hot wire capacity (meaning current), that all depends on what the gauge is, and its fuse.
But as to what you can tap from it you have to know what else it supplies - ie, how much that draws.
They should all take 12V (meaning up to 16V in practice). That's a function of insulation.
I'd suggest your own hot fuse and wire unless perhaps you will only use low current.
And be warned - some cig sockets are not good for currents above a few Amps. (Consider using the smaller and superior Euro sockets aka "Merit" and other names. They are rated to 20A and are fast more secure - especially in a vibrating environment.)
For image URLs, merely use the 'tree' icon in your Reply/edit window, or the "arrow tree" for images off your PC/disk. Image names must be limited to about 10(?) ordinary characters - at least for PC uploads.
Use the "Preview Post" button to confirm before "Post Reply". If only blank squares are shown, it hasn't loaded properly (long name or invalid characters).
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Member - Posts: 4
Member spacespace
Joined: January 19, 2014
Posted: January 22, 2014 at 4:02 PM / IP Logged  
Great, this answers alot of questions, thanks for your time replying. I am going to revise my schematic and post another one (so you can actually see it this time)
Many thanks,
Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: January 23, 2014 at 3:47 AM / IP Logged  
Ah thanks.
What would be handy to know is the load you intend to run.
A phone charger or tablet may be quite or reasonably low - eg 5W - 30W, or ~0.5A to ~3A as opposed to another battery, or a HU (10A?) or hair dryer (20 - 200A) or big amp (400A). Yes - I'm being a bit a lot ridiculous dual power socket for honda cb500s - Last Post -- posted image. dual power socket for honda cb500s - Last Post -- posted image.
But reply when you have your updated schematic etc.
I might have a look at your bike's wiring in the meantime... (That's a MIGHT...)
Member - Posts: 4
Member spacespace
Joined: January 19, 2014
Posted: January 23, 2014 at 3:18 PM / IP Logged
Ok, this should be accessible, although I still need to play around with posting the actual image instead of the link when I have a bit more time. Apologies for sub-par tablet drawing, I did have a neater one until somebody told me it was all wrong.... dual power socket for honda cb500s - Last Post -- posted image.
I will be using satellite navigation unit occasionally, and vehicle usb adapter to charge phone/tablet etc, so not too much draw.
Many thanks,
Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: January 23, 2014 at 10:27 PM / IP Logged  
Your pic but cropped and 1/12th its original filesize....
dual power socket for honda cb500s - Last Post -- posted image.
Reverse the LED direction ie, line end (Cathode) towards GND.
And the resistor could be upped to 680 Ohms (1/2W) to ensure the LED's 20mA is not exceeded if running at 14.4V etc. (It shouldn't make a significant difference to brightness.)
I'd probably reduce the fuse size since many cig sockets are likely to flame at 15A; sometimes even 10A, or less - and since your loads will probably be much lower.
Decide your max current draw and add 20-30% and round off to the next available fuse eg 5A, 10A, or even 7.5A.
And to reinforce what I said earlier (and in diodes ve direction only?) - isn't it great that we only care about conventional current flow and not electrons or anions etc?
That's how I picked your back-to-front LED. Its arrow points the wrong direction for current to flow thru it (from +ve to -ve THRU the circuit).
And since all electronic component symbol arrows show conventional current flow (LEDs, diodes, transistors, FETs, etc) why worry about the flow direction of electricity?   
BTW - wrecking your neat pic - barstard! (Probably the same B that killed Kenny.)
But your latest is IMO beautiful - better than any CAD!
Member - Posts: 4
Member spacespace
Joined: January 19, 2014
Posted: January 25, 2014 at 10:19 AM / IP Logged  

Ok then, I have reversed the diode direction on my schematic (also read up on conventional current flow), changed the resistor to 680ohm and changed the fuse to a 7.5amp blade type. Although on the box for my dual power socket I am told that it can take 25 amps, which it may, but I doubt my phone/tablet/satellite navigation unit will take that!

The only thing that I am now wondering is where to get the power from, on my bikes schematic, I am assuming that all of the green wires are positive, and that they are all the same voltage/amperage. I am also assuming that I can ground it to the chassis? I will have a look where other things have been grounded. Could you recommend any software that I could use to draw schematics? I am resorting to scanning in hand drawn ones, but that is proving quite annoying when they need a small alteration and I have to re-draw/scan them all again!!

Thanks again, you have been very helpful.

Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: January 26, 2014 at 3:13 AM / IP Logged  
Re the wiring diagram you linked earlier...
It shows the battery goes thru a 30A fuse to the rest of the bike EXCEPT the startermotor heavy cable which is direct to the battery +12V when cranking. (See the starter motor on the top right corner.)
BTW - diagram orientation assumes 'right way up' - ie, landscape mode.
From that startermotor relay 30A fuse it goes (down) to the alternator's voltage regulator; or (left) to the IGN switch.
IGN then switches 30A +121V to Fuse #1 (10A) & direct down to the fan motor whose fan switch connects it to GND;
and to fuses 2, 3, & 4 for +12V to all other circuits(10A, 15A, 10A).
In short, every OEM electric load in that diagram requires the IGN to be on except PERHAPS the fan motor especially if IGN switch does more than simple on-off (eg, off-acc-IGN, Park-off-IGN).
And of course the starter motor heavy +12V terminal which is connected direct to the batt's +12V terminal.
IMO you do want it switched thru IGN hence either power from one of those switched fused circuits 2, 3, or 4 (see below) else similarly switch a 4 or 5 pin aka SPST or SDPT relay coil to connect its Common 30 - the Dual Socket Power +12V...
and NO Normally Open 87 via your added 7.5A fuse with maybe a 10A or 30A distribution rating.
Ideally you'd know the max else typical load on any fuse and decide which has the best spare capacity. (If total fuse amperage is exceeded, it could take seconds or hours to blow.)
Otherwise take a chance and move if necessary,
Or if the fuse holder etc and all the wiring off the 10A fuses is suitable for - and hopefully the same as existing - 15A circuit wiring. If so, it should be acceptable to tap into that +12V feed anywhere and upgrade from a 10A to 15A fuse (and hence have a known 5A available). But it should not be a critical circuit - eg, headlights, brake lights.
A relay solves all the above in that you can guarantee all the raw current you need up - ignoring battery limits, life & safety aspects - to the limit of YOUR added fused-cable's rating direct to the unfused battery +12V terminals yet IGN off should guarantee all loads are off...
Unless like me you also want a manual bypass so you can charge your accessories with the IGN off, either diodes between IGN & the manual switch and the relay;
or grounding control - eg, insert a fuse to bypass the IGN key.
dual power socket for honda cb500s - Last Post -- posted image. As I've been meaning to do to my HU's power relay, but the IGN-on requirement to turn & then stay on independent of the IGN key IMO isn't too bad - unless I'm camping...   And electric windows, but they are already on +12V (I learned from my previous mistake!) but that ain't good security... dual power socket for honda cb500s - Last Post -- posted image.
So, a few considerations or solutions...
I would ignore the claimed "25 amps". How can it be if those sockets are specified to only 15A - and many IMO have failed to meet that - what additional protection is there for sub-25A rated loads many of which will not be fused if rated to carry 15A?
IMHO that's dangerous!.
Hence reduce the single-socket capability to 15A unless it can only handle less. Or try a reasonably safe size (eg 1A or 2A, usually 5A, but above 10A must be checked) and see whilst checking for hotspots (warm wiring or switches or GND connections) a few times and thereafter reasonable intervals.
And oh boy, I don't think my day is one involving good expression...

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