n00b needs help with ohm question.

[handsomeryan]

I want to build an LED scanner like the 'classic' led scanner @ http://www.bit-tech.net/modding/2002/06 ... ht_rider/2

I am trying to source the parts via Mouser.

the parts list calls for a 4.7K and a 220K potentiometer but the closest i could find were 5K and 250K. I don't have a good enough understanding of electronics to know if i can make these substitutions? if i can substitute- am i supposed to go low or high on the ohm rating?

Any help would be appreciated.

[adafruit]

those values are totally OK substitutions

[handsomeryan]

Okay, i did a little more research...

to quote Howstuffworks.com:

A neat analogy to help understand these terms [voltage, current, and resistance] is a system of plumbing pipes. The voltage is equivalent to the water pressure, the current is equivalent to the flow rate, and the resistance is like the pipe size.

I also found a fancy diagram of Ohm's law @
http://www.the12volt.com/ohm/ohmslaw.asp

including the passage: A very high resistance allows a small amount of current to flow. A very low resistance allows a large amount of current to flow.

and using the calculators @ http://www.the12volt.com/ohm/page2.asp I determined for the 220K Potentiometer:

if the incoming voltage is 12V and the resistance-
is lower @ 2K ohms the power is 0.00072 watts
follows the instructions @ 2.2K ohms the power is 0.00065 watts
is higher @ 2.5K ohms the power is 0.00058 watts

so my 2 options are almost evenly split @ 12% underpowered or 11% overpowered. (assuming my math is correct)


I am still not really sure if this difference is critical, or which way to go, overpowered or underpowered?

EDIT: Thanks ladyada!