Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: mdmedlin on March 29, 2009, 07:45:12 AM

Title: resistors for the $50 robot
Post by: mdmedlin on March 29, 2009, 07:45:12 AM

I have a quick question, or actually a few quick questions.  I am making the photoresistors for the 50 robot and I have a question.  Do I use 1/4 w or 1/2 w resistors?  Does it matter which ones I use.  I have noticed that for the LED, I need a 1/4 and for the board, I use a 1/2.  I used the 1/4 because they seemed to be the same size as the ones in the picture.  Also, does it matter what color the resistor is?  I have seen blue and yellow resistors.  Does that make a difference?  Thanks

Title: Re: resistors for the $50 robot
Post by: Razor Concepts on March 29, 2009, 09:04:08 AM

1/4 is fine for the photoresistors.

There is basically no difference in functionality between the blue and yellow, the blue resistors are just metal-film resistors and the yellow are carbon resistors.

Title: Re: resistors for the $50 robot
Post by: GearMotion on March 29, 2009, 09:54:50 AM

Quote from: mdmedlin on March 29, 2009, 07:45:12 AM

I have a quick question, or actually a few quick questions.  I am making the photoresistors for the 50 robot and I have a question.  Do I use 1/4 w or 1/2 w resistors? 

Resistor in series with a photoresistor? (right?) There is very little current flowing through that, so 1/4 (even 1/8) is fine with such low currents.

Title: Re: resistors for the $50 robot
Post by: Admin on April 08, 2009, 12:50:04 AM

remember:

power (watts) = voltage * current

voltage = current * resistance

so:

power = V^2/R

plug in the numbers, and you'll determine the power that goes into that resister is incredibly small.