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Mechanics and Construction => Mechanics and Construction => Topic started by: rahulpwns on November 19, 2011, 08:07:53 PM

Title: Ohm's Law
Post by: rahulpwns on November 19, 2011, 08:07:53 PM

hey,
i need help with calculating the amount of ohms my resistors need to be with ohm's law.
i have a sensor that has an Operating voltage of 5v and a max current of 25mA.
would i do 5v/.025A?

-rahulpwns

Title: Re: Ohm's Law
Post by: Soeren on November 19, 2011, 08:51:05 PM

Quote from: rahulpwns on November 19, 2011, 08:07:53 PM

hey,
i need help with calculating the amount of ohms my resistors need to be with ohm's law.
i have a sensor that has an Operating voltage of 5v and a max current of 25mA.
would i do 5v/.025A?

-rahulpwns

Since you don't like using Google to get your answers, let us do your footwork and direct you towards this calculator (http://www.crownaudio.com/apps_htm/designtools/ohms-law.htm) combining Ohms Law and Watts Law ;)

Title: Re: Ohm's Law
Post by: Gertlex on November 19, 2011, 08:51:39 PM

That would indeed give you a value of Ohms, but the rest of us have no idea what sensor you're using, and therefor whether what you're doing makes sense...

Title: Re: Ohm's Law
Post by: rahulpwns on November 19, 2011, 11:53:13 PM

sorry if i came across as too vague.
@soren i have been researching the formula, but i have not come across a site which has helped me understand what values of current to use.
here is the link to the sensor:
http://www.pololu.com/catalog/product/959 (http://www.pololu.com/catalog/product/959)

Title: Re: Ohm's Law
Post by: bens on November 20, 2011, 12:02:58 AM

Hello.

That sensor already has a current-limiting resistor for the IR LED built-in.  You do not need an external resistor to use it.

- Ben