UPS for a wifi router - Page 1
Forum section: electronics / projects

author: justin66
author_rank: Regular Contributor
timestamp: April 05, 2015, 03:38:39 am
content: well i was wondering how to make what the title says wifi router UPS its i want it to be 5v dc i guess 1 amp of max load will be more than enough i would like it to be abble to handle 5 minutes of work witch two 9v batteries can easily do it shouldnt necesseraly be a 9v it could be other batteries maby lead acid but im not sure its ok for this project. how do i do it? also mabyi could power it from one 4.5v but tham i would need dc to dc converter please guys help me out

author: BradC
author_rank: Super Contributor
timestamp: April 05, 2015, 03:56:13 am
content: Why not grab a 12V lead acid battery and a cheap USB adapter for a car.12V to 5V @ 2.1A and available cheaply _everywhere_. You could not make one for near the cost of those little buggers.I have one powering an ASUS WL-330g WAP.You could just put a 13.8v power supply on the battery to keep it floated. The only issue you will have is limiting the initial charge current when the battery is being charged from flat.

author: RobertHolcombe
author_rank: Frequent Contributor
timestamp: April 05, 2015, 05:18:23 am
content: Quote from: BradC on April 05, 2015, 03:56:13 amUse a UVLO to stop the battery being completely drained

author: justin66
author_rank: Regular Contributor
timestamp: April 05, 2015, 07:21:34 am
content: thanks

author: cosmicray
author_rank: Frequent Contributor
timestamp: April 05, 2015, 12:31:32 pm
content: Quote from: BradC on April 05, 2015, 03:56:13 amFor that matter, get a 6V golf cart battery. Put 1 or 2 rectifiers in series to act as 0.7V drops. Much longer discharge curve than a car battery.

author: BradC
author_rank: Super Contributor
timestamp: April 05, 2015, 02:46:49 pm
content: Quote from: cosmicray on April 05, 2015, 12:31:32 pmAgreed, but who said anything about a car battery?

author: DanielS
author_rank: Frequent Contributor
timestamp: April 05, 2015, 03:24:59 pm
content: Routers usually have their own internal DC-DC converters to step down 5-12V input to the 3.3/2.5/1.8/1.5V they need internally. I suspect most of them will be fine with any input voltage over 4V as long as the adapter can provide the increased current at lower voltages.I have three Linksys routers and all three of them have an input that appears to be designed to take 12V input regardless of whether the stickers say 5V or 12V. They also work fine with either input voltage.

author: richard.cs
author_rank: Super Contributor
timestamp: April 05, 2015, 06:07:08 pm
content: Quote from: DanielS on April 05, 2015, 03:24:59 pmSeconded.All of my network gear is 10V or 12V input but on cracking it open and checking everything had a switcher with at least 20V input rating and generally worked down to about 5V. Most of mine have a switcher to 3.3V and a linear regulator for any lower supplies. They work wonderfully from a float-charged lead-acid. :-) I wouldn't go very far out of spec without opening them and checking what parts are used though.For my stuff I effectively diode-OR an 18V laptop brick and a 12V lead-acid that's charged from a linear regulator off the 18V supply. In practice I chose a PFET LDO that saturates hard when it drops out of regulation, it then conducts perfectly the wrong way.