"Ring main" of 5v USB sockets for the boat

sarabande

sarabande

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Many comms devices and small LED lights seem to work off 5v USB sockets, and prompted by offspring's comment that I have only 1 USB charger socket on board (from a cigarette lighter socket at the chart table) I was wondering about having, say, 6 USB sockets distributed round the boat.
The alternative of a cigarette lighter socket is bulkier, and requires an adapter at each one.

Is it best to use a small "buck" (?) transformer from the normal 12v supply, at each point, or to go for a decent 12v - 5v transformer near the electrics centre, and run 5v cables in a ring main ? Voltage drop is a more of a question perhaps at lower voltages ?

Trying to reduce points of possible failure, for reliability's sake, whilst providing a flexible source of power for visitors.
 
For many devices you need to also set up refrence voltages on the other USB pins as well as the 5v that acts as the main power supply. This can be done, but it not as simple as just providing the 5v.

Many comercial 12v USB chargers (which have the correct refrence voltages) are the same size as cig socket, so often it is a simple matter to change, but the better units (high power and low consumption ) are not cheap.
 
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Very tricksey question.
From a stable 5V side then regulation at each socket wins hands down. But (There's always a but) cheap buck converters are notoriously noisy in an rfi way and most USB devices aren't all that fussy.
If you wanted to install a Rolls Royce of 5V distribution then a central power supply with a r emulated output for each socket with wiring to include a no-current sense wire back from the sockets so the supply can counter the effects of volt drop.
 
sarabande said:
Many comms devices and small LED lights seem to work off 5v USB sockets, and prompted by offspring's comment that I have only 1 USB charger socket on board (from a cigarette lighter socket at the chart table) I was wondering about having, say, 6 USB sockets distributed round the boat.
The alternative of a cigarette lighter socket is bulkier, and requires an adapter at each one.

Is it best to use a small "buck" (?) transformer from the normal 12v supply, at each point, or to go for a decent 12v - 5v transformer near the electrics centre, and run 5v cables in a ring main ? Voltage drop is a more of a question perhaps at lower voltages ?

Trying to reduce points of possible failure, for reliability's sake, whilst providing a flexible source of power for visitors.
Click to expand...

You can build your own outlets using DC-DC converters, i have a couple i made myself that will charge up to 3a, but it's a bit of extra work to make them and install everything. For simplicity i'd suggest some good quality, off the shelf sockets, these work well :

https://www.asap-supplies.com/double-usb-cigarette-lighter-socket-715661

Don't buy cheap ones from Ebay, Amazon etc, they are not reliable. I bought three from Ebay for my own boat a while back and one was putting out 12v, one was nothing and the other one less than an amp, the 12v one fried a brand new tablet. No need for a ring, fit them on a radial circuit, with a separate fuse for each one, if need be fit a small blade fuse box.
 
I would use individual USB converters (not generic 5v DC-DCs) at each location -

  • I suspect volt-drop might be an issue with only 5 volts to start with
  • There's a whole mess of ad-hoc standards for telling different kinds of devices how much power they're allowed to draw, by putting different resistances on the data pins etc. Easier not to have to research and implement that yourself. This is why you want USB supplies not generic converters.
  • If you just add up say 2.5a per socket and multiply by number of sockets, you have a reasonably beefy supply and the ability for all of it to be drawn through any one socket. This would worry me a little especially with some very cheap and shoddy USB devices about.
  • The argument about "reducing points of possible failure" is moot because the multiple converters aren't depending on each other like links in a chain. Instead the situation is one of redundancy vs all eggs in one basket.

Incidentally the idea of wiring it in a ring is weird and unnecessary.

Pete
 
prv said:
I would use individual USB converters (not generic 5v DC-DCs) at each location -

  • I suspect volt-drop might be an issue with only 5 volts to start with
  • There's a whole mess of ad-hoc standards for telling different kinds of devices how much power they're allowed to draw, by putting different resistances on the data pins etc. Easier not to have to research and implement that yourself. This is why you want USB supplies not generic converters.
  • If you just add up say 2.5a per socket and multiply by number of sockets, you have a reasonably beefy supply and the ability for all of it to be drawn through any one socket. This would worry me a little especially with some very cheap and shoddy USB devices about.
  • The argument about "reducing points of possible failure" is moot because the multiple converters aren't depending on each other like links in a chain. Instead the situation is one of redundancy vs all eggs in one basket.

Incidentally the idea of wiring it in a ring is weird and unnecessary.

Pete
Click to expand...

^This.
 
prv said:
I would use individual USB converters (not generic 5v DC-DCs) at each location -

  • I suspect volt-drop might be an issue with only 5 volts to start with
  • There's a whole mess of ad-hoc standards for telling different kinds of devices how much power they're allowed to draw, by putting different resistances on the data pins etc. Easier not to have to research and implement that yourself. This is why you want USB supplies not generic converters.
  • If you just add up say 2.5a per socket and multiply by number of sockets, you have a reasonably beefy supply and the ability for all of it to be drawn through any one socket. This would worry me a little especially with some very cheap and shoddy USB devices about.
  • The argument about "reducing points of possible failure" is moot because the multiple converters aren't depending on each other like links in a chain. Instead the situation is one of redundancy vs all eggs in one basket.

Incidentally the idea of wiring it in a ring is weird and unnecessary.

Pete
Click to expand...
I have just put in 12 v wiring to ciggie lighter sockets and use separate plug in chargers
 
ctva said:
And a lot of the cheap USB sockets kill VHF and FM radio signals. I tried and dumped them..
Click to expand...


Can you remember which ones? Would be handy to know who the culprits are.

I just had an RF look at the generic amazon dual 2.1A/1A ones I have installed, hard to detect any noise even with an antenna touching, this using a Funcube pro plus usb receiver.
They do pull 18mA just powered up with nothing plugged in though.


JLFbewG.png


More than can be said of the fridge - noisy as !@#$ all over the place (not up to FM or VHF though!

oPFLqfk.png
 
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thanks MacD, those look the business. 2 USB, cigar socket ([posh !) from a 12v source with built-in down transformer, what's not to be missed !

Oh yes, any interference to other electronics from them please ?

And that Amazon voltage data gadget looks very neat too.


PRV - thanks for analysing the issues more eloquently than I did,. And also to all the other contributors for rummaging around the problem and providing such useful info and answers.
 
sarabande said:
Oh yes, any interference to other electronics from them please ?

And that Amazon voltage data gadget looks very neat too.
Click to expand...

Afraid I can't say for the 12V Planet ones: they were just an example of type. Mine were sourced from elsewhere and give no evident interference. Unfortunately I can't recall where that 'elsewhere' was. Sorry.

The USB meter is reassuring. One might have saved Paul from frying his tablet. (Sorry, PR: sympathy rather than a dig.)
 
lw395 said:
^This.
Click to expand...

^That.

A proper USB power supply is a lot more complicated than two pins with 5V across them. As far as I can see, many devices will only draw 0.5A from a dumb supply of that sort - for 2.1A (or whatever) they need to be able to talk to the supply to make sure it's up to it.
 
JumbleDuck said:
^That.

A proper USB power supply is a lot more complicated than two pins with 5V across them. As far as I can see, many devices will only draw 0.5A from a dumb supply of that sort - for 2.1A (or whatever) they need to be able to talk to the supply to make sure it's up to it.
Click to expand...

This is why the reference voltages are needed on the other pins.

While they make the wiring more complicated they are simple fixed voltages rather than an active two way communication system.

However, it does mean if you only supply 5v to the charging pins many devices will not charge, or will only accept a low charge level even if the power supply is capable of delivering high current.
 
macd said:
Afraid I can't say for the 12V Planet ones: they were just an example of type. Mine were sourced from elsewhere and give no evident interference. Unfortunately I can't recall where that 'elsewhere' was. Sorry.

The USB meter is reassuring. One might have saved Paul from frying his tablet. (Sorry, PR: sympathy rather than a dig.)
Click to expand...

No problem Mac, i did buy one after the tablet died :)
 
I think if OP tries to produce his own 5v ring system for his boat that the actual USB sockets are difficult to get difficult to connect to and as said there are tricks to the wiring. All this will force him to go for the cheap and available 12v cigar lighter socket type converter with USB socket. olewill
 
You'll be wanting Qualcomm's Quick Charge or USB-C soon enough - they can charge newer phones at twice the rate, and I can even run my Macbook off USB-C.

Stick to good quality 12v lighter sockets and appropriate USB adaptors.
 
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