Need 12V stable power supply for WIFI router

[SFH]

Originally Posted by senormechanico

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.

Dr. Phil

The Ubiquity Bullet POE needs 24V and the router 12V. How did you wire that up?

Steen

[jeepbluetj]

Originally Posted by tpkas

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.

Regards,

Brian

Or use a 7812 and save 2 resistors.

Doesn't matter anyway, in all likelihood there's a regulator of some sort from the wall wart socket to the rest of the stuff in the router - it runs at 3.3v or 5v inside. I'd take it apart to look, but that's me.

[hellosailor]

I'd use a 7812 or 7912 instead of an LM317. There's no need for additional parts, no adjusting, and the chip is significantly cheaper. The regulation is the same for all purposes. Makes for real simple building. Filter capacitors really aren't needed for this type of simple stuff, and the chip should handle the same 1.5A if bought in the right package.

[jcapo]

Originally Posted by SFH

Dr. Phil

The Ubiquity Bullet POE needs 24V and the router 12V. How did you wire that up?

Steen

My Bullet works fine on 12 volts from the batteries.

[senormechanico]

Originally Posted by SFH

Dr. Phil

The Ubiquity Bullet POE needs 24V and the router 12V. How did you wire that up?

Steen

I'm not a doctor, but I went to one once...

The Ubiquity Bullet will work on UP TO 24 volts, but does not NEED 24 volts.
It has an internal power supply that increases current draw as voltage drops.
The actual guts of the transceiver probably see a constant voltage as a result.

Before installing mine on the masthead, I hooked it up to a variable DC supply and a volt meter and ammeter, and sure enough, it draws twice as much current at 12 volts than it does at 24. It's still an insignificant amount either way. At 12 volts, the Bullet and the Netgear router draw about a half amp combined total.

[Paul Elliott]

Originally Posted by jeepbluetj

Or use a 7812 and save 2 resistors.

Doesn't matter anyway, in all likelihood there's a regulator of some sort from the wall wart socket to the rest of the stuff in the router - it runs at 3.3v or 5v inside. I'd take it apart to look, but that's me.

If you want 12V out, you can't use a 317 or 7812-type regulator. These are great linear regulators, but they require that the input voltage be at least 2V greater than the regulated output voltage. If you set one up for 12.0V output and feed it with (say) 13V, the output will be somewhere around 10.8V and will not be regulated. Feed it with 10V and the output will be less than 8V.

You need a switcher, not a linear regulator. For the router you can probably get by with a good direct battery connection, and forget the regulator. The battery gives you a pretty clean voltage, but transient protection is good to have. I would be reluctant to use a bare 15V zener for that though, since the transient current will probably fry the diode. A resistor / inductor / capacitor / zener circuit would be safer.