Author Topic: Did I get my measurements wrong? 6.5 watts doesn't deem right  (Read 2322 times)

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Offline Hawaii00000Topic starter

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Did I get my measurements wrong? 6.5 watts doesn't deem right
« on: December 23, 2009, 01:03:38 AM »
So I'm trying to see what resistor I can use with my arduino. I though I would be able to use a 1/4 watt resistor, but according to my multimeter it puts our about 5v at 1.3 amps. So I put the numbers into a handy power calculator (http://www.crownaudio.com/apps_htm/designtools/ohms-law.htm) and got an output of 6.5 watts. That doesn' seem right. Did I do something wrong?
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Offline SmAsH

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Re: Did I get my measurements wrong? 6.5 watts doesn't deem right
« Reply #1 on: December 23, 2009, 01:34:11 AM »
What puts out 1.3 amps?
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Offline madchimp

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Re: Did I get my measurements wrong? 6.5 watts doesn't deem right
« Reply #2 on: December 23, 2009, 07:29:59 AM »
Well if your arduino is drawing 1.3 amps at 5v then it is using 6.5 watts.  However that 6.5 watts is for the whole circuit and your resistor doesn't need to be able to handle that it only needs to be of a high enough wattage to be able to handle the power it dissipates which would be the voltage drop across the resister multiplied by the current going through the resister. If you explain in more detail what you are doing with the resister I'm sure someone can help you further.
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