### Author Topic: resistors for the \$50 robot  (Read 1109 times)

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#### mdmedlin

• Full Member
• Posts: 73
##### resistors for the \$50 robot
« 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
Do or do not, there is no try yes I changed my picture, it is of my daughter.

#### Razor Concepts

• Supreme Robot
• Posts: 1,856
##### Re: resistors for the \$50 robot
« Reply #1 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.

#### GearMotion

• Supreme Robot
• Posts: 489
• Two decades+ of Embedded Design
##### Re: resistors for the \$50 robot
« Reply #2 on: March 29, 2009, 09:54:50 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.

• Supreme Robot
• Posts: 11,632
##### Re: resistors for the \$50 robot
« Reply #3 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.