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Old 08-06-2015, 11:27   #1
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Need 12V stable power supply for WIFI router

Hi,

I have setup a D-link 921 4g Wifi router to pass-on information from my Victron CGCX to the Internet and to provide WIFI on board.

It is now supplied directly through a 230V to 12V/1A adapter but I would like to supply it directly from my 12V service bank to get rid of the power adapter and to avoid running the inverter.

Any ideas on how to get a stable 12V supply without spikes from alternator etc.?

Thanks
Steen
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Old 08-06-2015, 12:22   #2
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Re: Need 12V stable power supply for WIFI router

You can use one of these devices..

LM2596S Power Module DC TO DC Buck Converter Step Down Module | eBay

I doubt you need it though. I suspect your router will have a very similar circuit built in and will be quite tolerant to voltage spikes.
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Old 08-06-2015, 13:56   #3
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Re: Need 12V stable power supply for WIFI router

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Originally Posted by travellerw View Post
You can use one of these devices..

LM2596S Power Module DC TO DC Buck Converter Step Down Module | eBay

I doubt you need it though. I suspect your router will have a very similar circuit built in and will be quite tolerant to voltage spikes.
Thanks. Will give it a try and see if the router can handle it

/Steen
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Old 08-06-2015, 14:26   #4
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Re: Need 12V stable power supply for WIFI router

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Originally Posted by travellerw View Post
That's not going to work for him. I have several of those and have used them in various electronics projects. They work great for what they are, but they just pass through voltage, and you lose a bit in the process. That is, if you need 12.0 volts coming out, you are probably going to have to supply very close to 13 volts going in. In addition, if the input voltage fluctuates then the output voltage will fluctuate also. They work wonderfully when, for example, you have a 5 volt wall wart and need 3.5 volts for your latest project (which is how I just used one).

For his needs, I think this is what he is looking for...
https://www.pololu.com/product/2577
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Old 08-06-2015, 14:59   #5
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Re: Need 12V stable power supply for WIFI router

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That's not going to work for him. I have several of those and have used them in various electronics projects. They work great for what they are, but they just pass through voltage, and you lose a bit in the process. That is, if you need 12.0 volts coming out, you are probably going to have to supply very close to 13 volts going in. In addition, if the input voltage fluctuates then the output voltage will fluctuate also. They work wonderfully when, for example, you have a 5 volt wall wart and need 3.5 volts for your latest project (which is how I just used one).

For his needs, I think this is what he is looking for...
https://www.pololu.com/product/2577
You are incorrect. They only fluctuate voltage when the voltage drops, not when it spikes. They will block spikes up to 40V! I have used them for many 12v devices as most 12v devices are voltage tolerant between 9v-16v. Since a charged 12V battery voltage (LA) is 13.2V-13.4v they will supply 12V most of the time. The voltage will drop to about 11V once the battery is completely depleted (which it should never be). Those boards will reliably supply 1A @ 12V and barely get warm.
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Old 08-06-2015, 15:52   #6
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Re: Need 12V stable power supply for WIFI router

A "spike" is not the same as normal voltage fluctuation during charging cycle.

In fact boat electrical systems are usually very free from spikes, as the battery bank absorbs those. Check the router's power supply rating -- does it need straight 12v? Or is it 10v -- 15v or something like that? It will need to be at least 12v -- 14.5v to deal with normal fluctuations of voltage.

Otherwise, use a DC-DC converter. Victron make good ones. They make a 100 watt one which can take anything from 9 volts to 140 volts DC and turn it into stable 12.5 volts output. http://www.victronenergy.com/upload/...verters-EN.pdf There are others like that on the market too.
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Old 08-06-2015, 15:56   #7
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Re: Need 12V stable power supply for WIFI router

Thanks Dockhead

I was actually looking for a Victron DC-DC converter initially. Found it on page 2

12.5V should be safe I guess

Thanks
Steen
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Old 08-06-2015, 16:14   #8
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Re: Need 12V stable power supply for WIFI router

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Originally Posted by SFH View Post
Hi,

I have setup a D-link 921 4g Wifi router to pass-on information from my Victron CGCX to the Internet and to provide WIFI on board.

It is now supplied directly through a 230V to 12V/1A adapter but I would like to supply it directly from my 12V service bank to get rid of the power adapter and to avoid running the inverter.

Any ideas on how to get a stable 12V supply without spikes from alternator etc.?
When selecting a power 'pick-up' point, the closer you are to the batteries, the fewer spikes and disruptions there should be.

But anyway, I think you'll find that there are already regulators and such inside the D-Link router, because most digital logic runs at 5v or 3.3v, so the router should already have some immunity to spikes on the 12v DC power.

For even more regulation and protection, one of these would be a better option than a 2596-type regulator, because the 2596 ones are only step-down, while the linked ones can also boost... meaning they can deliver 12.0 v out even if the input ranges from 10 to 16v.
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Old 08-06-2015, 16:46   #9
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Re: Need 12V stable power supply for WIFI router

Many, by now possibly most or all, "12 volt" routers are taking 12v and dropping it to 5v internally. Once an external power supply goes out for UL testing, it costs $50,000 to submit for testing, pass or not. I expect CE and EU testing may cost the same. So, the external power brick and voltage level are 'set' and it becomes often cheaper to simply stick to the standard that has already been paid for. (That's also why the adapter is external, not a "new" one requiring new certification fees on each new device.)


I'd simply add in five bucks worth of spike protection to a direct 12v line to the batteries. A couple of "transzorbs" or other spike protectors, maybe a 15v zener diode (since the ships' supply should never exceed 14.4 normally), there are a number of cheap components, like $1 a piece, available for this purpose from electronics suppliers. Radio Shack, Mouser, Digi-Key, Newark Electronics all here in the US.


They will do the job as thoroughly as anything you can buy in a fancy box, you just solder or crimp positive and negative to the corresponding sides of your router supply line.


While you are at it...there is major disagreement as to whether spikes (from the starter and alternator during engine startup and shutdown) are or aren't normal and dangerous.


It isn't that much harder to put a little more capacity into a spike protection device(s) across the power line that feeds "all" the nav system, or all the electronics, as well as any radios you have on board.


A number of major vendors say the spike problem is real, and that they don't put spike protection in their equipment because 1)It adds costs, and 2)It eventually can fail anyway, so 3)It would just make their products less competitive. And it is SO easy to add to any system, externally.
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Old 08-06-2015, 18:51   #10
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Re: Need 12V stable power supply for WIFI router

Also consider going to a router that takes nominal 5V from a USB style power connection. I have a multiport USB power supply (nominal 12V input) which runs my router (TPLINK mini router) and has ports left over for charging all those other personal electronics that take 5V these days.

Though its DC to DC, I assume there is some loss but nothing like going thru an inverter/power supply combination.
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Old 09-06-2015, 03:51   #11
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Re: Need 12V stable power supply for WIFI router

I have previously hard wired a TPLink & now a Dovado Pro (both 12v nominal) into our system. It's own power line from the main panel & have never had any problems leaving them on 24/7.

Maybe I'm lucky.



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Old 09-06-2015, 09:32   #12
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Re: Need 12V stable power supply for WIFI router

Not the cheapest solution by a long shot, but a very solid one (in terms of its input tolerating all of the usual engine-start transients, voltage drops and surges, and providing a nice stable 12V output) can be had from Carnetix.com:

carnetix

I've used their product and it does all it's supposed to, and more. That said, I never quite got around to wiring it for my 12V TV/DVD, which was the original intent, but since the TV breaker is seldom on with the engine, it's been a non-issue thus far.

I did use the 5V output to run a small linux server (which is currently on a 5V USB iPad lighter-plug adapter, only because the Carnetix shuts down somewhere around -20C).

My Linksys WRT54G has been happy running directly on ship's 12V for a couple of years now.
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Old 09-06-2015, 09:36   #13
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Re: Need 12V stable power supply for WIFI router

I installed a Ubiquity Bulllet and a run of the mill Netgear AP several years ago.
I tossed the ac brick and used the DC output cable to wire it to the boat.
Both of them are on a single breaker/switch directly to the DC buss.
No problem ever.
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Old 09-06-2015, 09:52   #14
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Re: Need 12V stable power supply for WIFI router

+1 on hellosailor's 15v zener... make it at least 1 watt and put one on the load end of any 12v circuit that has sensitive electronics on it. Kills spikes... keep spares to use after lightning storms.
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Old 09-06-2015, 15:25   #15
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Re: Need 12V stable power supply for WIFI router

I use an LM317 voltage regulator for many low amperage circuits. I've included a picture of the circuit which is both very simple to build and is very inexpensive. I use this circuit to power a wifi router from my instruments server. It'll accept input voltages between 10v and 36v and output 12v.

Also, if you make R2 a variable resistor you can change the output voltage to almost anything under the input voltage. So if you need, say, 5v or 9v somewhere use the same circuit and just change the value of R2.

Regards,

Brian
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