richardabeattie
Active member
I have fitted a 12v twin socket - one side is a cigar lighter and the other a USB. But I cannot see any indication of the polarity. Does it matter? And should I wire them in series or parallel?
Wiring a USB Socket
- Thread starter richardabeattie
- Start date
jwilson
Well-known member
Yes it matters: I fitted similar a few weeks ago and there was + and - moulded in to the back of the sockets though not easy to see. Most plug-in charger-type stuff expects + at the pin of a cig-lighter socket..... And wire them in parallel, preferably with a fuse in the + feed. I used 20A as that was the max rating of the cig-lighter socket.
BERT T
New member
Personally I would not want a 20 amp fuse on a USB socket. I would suggest using 2 separate fuses, one for each probably a 15 amp on the lighter socket and a 2 amp on the USB socket
richardabeattie
Active member
Many thanks - I will peer more closely.
JumbleDuck
Well-known member
Although USB ports are normally only asked for 500mA at most (I'm simplifying a bit), many tablets use USB connectors to draw 2.1A. I'd use a 5A fuse.
JakeMM
New member
Another option would be to use a USB adaptor which plugs into the cigar socket. These can be had quite cheaply from eBay or play.com
William_H
Well-known member
I am a bit confused by this post. I understood all USB sockets provide 5v DC. This means there must be regulator to reduce 12v to 5v in the box. So yes polarity would be critical to the regulator and as said centre contact of the 12v socket always positive. The fuse can be 20 amp as max you could suck out of the 12v socket but the regulator should be able to control max current from USB. Or am I missing something here? good luck olewill
Lon nan Gruagach
Active member
More information will help, maybe a link to the suppliers page?, or part number or photo.
as has been said USB delivers 5V, if your socket does not contain a regulator then you might feed someone's iPhone with 12V, not pretty.
As a rule power outlesrs are nevere wired in series, unpluging one device will cut power to the other (as well as all sorts of jigger [pokery that happens if 2 are plugged in)
lpdsn
New member
He's referring to the USB sockets that the Chinese seem to be manufacturing by the million. Available on eBay and elsewhere for a fiver or so.
An example: http://www.banggood.com/USB-Socket-...o-Accessory-Power-Outlet-5V-21A-p-931962.html
Although that one appears a tad expensive (maybe there's the word marine mentioned somewhere in the description). The OP seems to have a double one with a 12V cigarette lighter socket & the USB charger socket.
They do give the right output. I fitted the first one about 12 months ago. No phones fried yet. Became so popular with crew I went back and fitted one in each cabin just to get their damned phones off the chart table.
Dockhead
Well-known member
Maplin sell good ones. They are 12/24 volts, and fit in flush in the cigar socket, converting it into a USB outlet. You can get them either as single or dual USB outlets. They put out a full 2 amps, so everything your IPlod can suck up. I've used them for a few years both on board and in the car; work great. And cheap as chips.
Rather than installing a dedicated USB port, I would just install (or use an existing) cigar lighter socket, and pop one of these in. In case you need the socket for something else, just pull it out.
Lon nan Gruagach
Active member
He's referring to the USB sockets that the Chinese seem to be manufacturing by the million. Available on eBay and elsewhere for a fiver or so.
An example: http://www.banggood.com/USB-Socket-...o-Accessory-Power-Outlet-5V-21A-p-931962.html
Although that one appears a tad expensive (maybe there's the word marine mentioned somewhere in the description). The OP seems to have a double one with a 12V cigarette lighter socket & the USB charger socket.
They do give the right output. I fitted the first one about 12 months ago. No phones fried yet. Became so popular with crew I went back and fitted one in each cabin just to get their damned phones off the chart table.
Aha, right then, 5V regulator is part of the socket, Wire them in parallel, fuse: max current draw @ 5V =3.1A ~=15W with 90% regulater efficiency gives ~1.25A @ 12V
Tintin
Well-known member
The + is very hard to see if you have bought the same one I did. I couldn't see it so guessed - 50% odds of being right.
I lost.
Burning smell. Bang.
New one needed.
Ho hum.
I lost.
Burning smell. Bang.
New one needed.
Ho hum.
lpdsn
New member
Never had a problem, but if result that bad might be worth trying to smear something white over it to highlight the +. A tiny bit of toothpaste perhaps.
Other thing, from memory, if the right way up, + was on the right looking from the front (I fitted one then went off to get the wires so had to memorise it). Obviously if it goes bang like Comrade Red's it was a left handed one.
Other thing, from memory, if the right way up, + was on the right looking from the front (I fitted one then went off to get the wires so had to memorise it). Obviously if it goes bang like Comrade Red's it was a left handed one.
richardabeattie
Active member
This is what I am trying to install. So I must look for the invisible polarity marks, wire it in parallel, fuse it at 5 Amps and hope the USB side delivers only 5 Volts.
http://www.12voltplanet.co.uk/user/...-cigar-lighter-socket-cars-boats-vehicles.jpg
http://www.12voltplanet.co.uk/user/...-cigar-lighter-socket-cars-boats-vehicles.jpg
prv
Well-known member
I have exactly the same one. Don't remember specifically how the polarity was marked, but I certainly didn't have any problem and I remember thinking it was a well-made piece of kit so the markings would have been obvious. Puzzled that you're apparently struggling - can you post a pic of the back?
Yes, the two halves should be wired in parallel, and the USB side will deliver the correct voltage - the worries upthread were from people who I'm afraid are out of date and had no idea what kind of device you were installing.
5 amps is too small really for the 12v side - lots of things you might want to plug in will use more than that. 15 might be more normal, a lot of sockets are rated to this although some are higher. There's an argument that the USB side should have an additional smaller fuse (haven't calculated it but your 5 amps sounds plausible) but personally I wouldn't (and didn't) bother. I just piggybacked the wires from one pair of crimped spade terminals across to the next.
Pete
richardabeattie
Active member
Thanks prv - it's on the boat so I can't post a photo of the back. I only realised I needed to get the polarity right after I'd installed it (but before I wired it up!). I'll take it out again and look at the back more closely.
prv
Well-known member
You could also just use a multimeter to test it in-situ. The button at the bottom of the 12v socket should be positive, the walls of it negative. Admittedly that's not much help for the USB side.
Pete
Tintin
Well-known member
It's the USB side that goes bang if wired wrong.
nigelmercier
RIP
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And this is the back, complete with + sign
![12V-24V-dual-twin-USB-power-socket-5V-2.1A-and-cigar-lighter-socket-cars-boats-vehicles[1].jpg](/proxy.php?image=http%3A%2F%2Fwww.12voltplanet.co.uk%2Fuser%2Fproducts%2Flarge%2F12V-24V-dual-twin-USB-power-socket-5V-2.1A-and-cigar-lighter-socket-cars-boats-vehicles%5B1%5D.jpg&hash=4144be916a7e0d23a7313cd41d149927)
More info http://www.12voltplanet.co.uk/12v-24v-dual-recessed-power-socket-twin-usb-5v-21a-cigar-lighter.html
As Pete says, no need to fuse the USB side with a smaller fuse.
Could I also suggest that these look much nicer if you discard the mounting plate, or mount it on the back of the panel.
Last edited:
richardabeattie
Active member
Yep that's the back and that's what I've got. Can't see the + in the photo but hope to spot it when I get back to the boat. Thanks everybody.
