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I have 3 WRT54G routers (12V), 1 voip gw (9V), 1 cable modem (9v) and a gbit ethernet switch (12v) which are all operating from their own adapters.

I planning to build a low power (probably 12V UPS) later on not just to power these but to power some computers through X3-ATX-300 300 Watt High Power 24pin DC-DC ATX.

As I understand transformators are all lossy especially these cheap power adaptors which these devices come with from China.

What I really care about is that the Watt consumption at the end. I realize it's not possible to calculate this in advance how much would I won with the switchover since that wattage shown in the devices datasheet is the possible maximum or not even an accurate data. The only way to see how much will I save with this is to use a powermeter plug all the adaptors into one electric switch which is connected to the meter then do the same thing with my all-in-one adapter.

How should I go with calculating how many amps max will my all-in-one transformator needs to provide?

Looking at these big brick power adapters for the WRTGs:

http://www.abrahamarama.com/wp-content/uploads/2007/08/linksys-ac-adapter.jpg

One can do 1Amp, I think it could easily power all 3 routers for example but I want to go for sure. How to calculate what powersupply will I need and which one should I buy which is the most efficient?

Thanks!

Defiler
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1 Answers1

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Your common power supply will need two outputs - 9VDC and 12VDC. You cannot expect the devices that use a 9V supply to work if you inject 12V into them. They may give the appearance of working for a while but finally meet an early end.

Alternatively you could simply use two power supplies, one with a 9V output and one with a 12V output.

Michael Karas
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