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Thread: Calculating Watts.

12242010, 02:38 PM #1
 Join Date
 Oct 2009
 Location
 Toronto
 Posts
 82
Calculating Watts.
Can someone explain to me how to calculate the watts for my connections so that I don't overload my circuit.
Some devices have the watts written on them and some don't.
For example, my ac adaptors say
input: 100120vac 50/60hz 1.0A max
output: 3.036vdc 3.0  0.41A
The above adaptor is comnnected to my O/C Master card.
How many watts is this adaptor pulling.
next.
USB Hub.
input: 100240 50/60hz 0.35A
output: 5v  2A
next
TQ.
input: 100240vac 50/60hz 2A
output: 12v  2A  5v  2A
Can someone tell me the watts these above things are pulling.
I'm in Canada, so the voltage here is 110.
thanks.
O' forgot to mention... also how to calculate the watts the computer is pulling.
My rig:
Asus P6T M/B
6GB Tri DDR3
Intel 1366 I7 920 D0
DVD Burner
2 Sata 7200 1TB Hard Drives
1 Gforce GTX 9800+
650 Watts Powersupply
Corsair H50 cooler
2 Chassie fans (120mm I think)
I don't know how much my computer is pulling.
I do have 2 more computers running for the PFD/ND and ECIAS but I would be abale to calculate those if I know how to calculate the above computer...
thanks.

12242010, 03:40 PM #2
 Join Date
 Jul 2013
 Posts
 948
Re: Calculating Watts.
If you have a multi meter with a good range then the best way is to measure the power (amps) being actually drawn by the appliance  this will not necessarily be the maximum output of the unit. Else you will have to use the maximum rating or make a judgement. You can then calculate the watts by using this link
http://www.csgnetwork.com/ohmslaw2.html
David

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12242010, 06:37 PM #3
Re: Calculating Watts.
Watt is the energy used. Watts is about the same on both sides of a power supply. Watt calculated like this:
volts x amps (also called VA)
Adaptor 110 x 1 = 110 watt
But why the output is written: 3.036vdc 3.0  0.41A i can't explain, but i belive that the greatest power in the whole area is 3 amp ( 3 x 36 = 108 watts, and 2 watts i power loss)
USB hub 5 X 2 = 10 watts
TQ Here is a large gap between indput and output.
110 x 2 = 220 wats
12 x 2 = 24 watts and 5 x 2 = 10 watts total: 34 watts.
The 2 amps could easily be a safety margin.
But if the only power consumption is only the 12 and 5 volts I belive that that max consumption is about 40 watts.
Abaut the computer power consumption I think the best solution is to buy this unit:http://www.gadgetgrid.com/2009/04/01...awattmeter/
Or you can read on the powersupply it's power consumption, then you have the maximum wattage
But remember that you always have approxematly the same wattage on input and output side (a little more on indput side). If not then is eternity machine is inventedLast edited by verticallimit; 12242010 at 06:38 PM. Reason: Ad some tekst
Sincerely,
Claus

12272010, 02:24 AM #4
 Join Date
 Oct 2009
 Location
 Toronto
 Posts
 82
Re: Calculating Watts.
hi and happy holidays guys.. thanks for the replies .. I still didn't quiet understand the above but I did order the above multimeter from amazon... should arrive in about 2 days.. Till I can learn how to do the above.. but thank you all for your replies.. appreciate it...
A/C

12272010, 09:16 AM #5
Re: Calculating Watts.
If you replace the mains with water pipes then it may be easier to understand.
The waterworks supplying water at a pressure of eg. 110, this corresponds to the voltage we get from the socket, in this case 110 volts.
We have a limit in consumption, a maximum number of volumes we can get out of the pipes, this water flow equivalent to amperes.
If we say that we max can consume 10 liters, then consumption = consumption x pressure = 10 x 110 = 1,100 liters. This corresponds to the max we can use from the socket 10 amps at 110 volts 10 x 110 = 1100 watt (watt can also be called VA)
Now we attach a device that can get water pressure to drop from 110 to 5 (transformer/powersupply), but we still want to use the 1100 liters.
Before we had a high pressure and fast flow of 110, now we have a low pressure of 5. To get the same out of the system at low pressure we must now cope with a Capacity of 110 / 5 = 22 times more, a large slow flow. Or we can say we transform from a thin pipe and over to a big pipe. When the voltage decreases then the Ampers get greater when we use the same wattage.
We consume the same 1100 liters (1100 watts), the pressure has cut emissions of 110 to 5 (volts), but Capacity (amps) is grown on lowpressure side.
So liters consumption is always the same, it will also say that Watts is always the same at high and low side.
Either it helped with the understanding, otherwise you even more confusedSincerely,
Claus

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12272010, 01:13 PM #6
 Join Date
 Jan 2007
 Location
 NEW ZEALAND
 Posts
 875
Re: Calculating Watts.
Hi A/C,
Claus is exactly right with what he said. To take a lot of confusion out and assuming your electronics is limited just follow what i have written;
1. Most if not all electronic equipment has a label stating the Votlage(V) and the Current(I) taken from the Power socket.
In your case Multiply V(Yours mains voltage in your case 110v) x I(Current listed on the product) = P(Power in Watts used)
Now you can add up all the watts you have connected to your mains socket.
In new Zealand here our Mais outlet sockets list the MAX CURRENT that one can safely take out and not Watts.
So now we say I(Current) = P(Watts)/V(volts (110) is the total safe Current you can take from this socket without overloading it.
In New Zealand we have 240v and a max per output of 10amps which = 2400 watts.
Hope this helps.
les
.

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01032011, 12:27 AM #7
 Join Date
 Oct 2009
 Location
 Toronto
 Posts
 82
Re: Calculating Watts.
Thanks Claus for the explaination... that really helped alot.. I have printed out your msg and will use it as reference whenever needed.. Excellent post..
Even though my meter arrived before the new year but didn't get a chance to play with it becuase of the holidays and family gatherings.. But learning how to calculate should always be in our minds incase our meters are playing mind games on us.. hehehe!!!
but thanks all for taking the time to explain me this..
Happy New Year and enjoy flying..

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