View Full Version : voltage / current / resistor question


TerenceT
08-23-2003, 03:46 AM
voltage equals current time resistance

V = I R

so i am going to get some LEDs for interior lighting that are
1.7vdc to 2.2 vdc

car voltage is 14 vdc to 12 vdc

so

(14vdc - 1.95vdc) / .035 = 344.3 ohms

??

ozbot87
08-23-2003, 11:20 PM
Yup.

BTW, what kind of LEDs are you getting? (Electrical Engineer here, so you can give me detailed info about them. :D )

TerenceT
08-24-2003, 02:23 AM
let's look at my shopping list...

interior dome light, front(2) and back(2), and passanger foot well (2)
10 red LEDs 2200mcd, 5mm, clear, 45 degree, 1.7-2.2 vcd, 20ma

exterior mirrors bottom, going to tap the door light, so they'll come on when i hit the remote
2 yellow, 1200mcd, 5mm, clear, 45 degree, 1.7-2.2 vcd, 20ma

Misc
1/2 watt, flame proof 10 ohm resistors
1/2 watt, flame proof 330 ohm resistors

was going to get diodes but give up finding them

TerenceT
08-24-2003, 02:31 AM
let's look at my shopping list...

interior dome light, front(2) and back(2), and passanger foot well (2)
10 red LEDs 2200mcd, 5mm, clear, 45 degree, 1.7-2.2 vcd, 20ma

exterior mirrors bottom, going to tap the door light, so they'll come on when i hit the remote
2 yellow, 1200mcd, 5mm, clear, 45 degree, 1.7-2.2 vcd, 20ma

Misc
1/2 watt, flame proof 10 ohm resistors
1/2 watt, flame proof 330 ohm resistors

was going to get diodes but give up finding them

ozbot87
08-24-2003, 03:04 AM
Good place to get parts such as diodes are:

Digi-Key.com

Or if you are a student, you can try to get samples from:

fairchildsemi.com
lite-on.com.tw

There are other LED manufacturers out there who might give you samples depending on the field of work you are in.

Hope this helps.

TerenceT
08-24-2003, 03:13 AM
thanks man
i'll keep the links but from partsexpress.com

the bill comes out to be 10 bucks plus shipping

note to others:

LEDs are not as expensive as people might think!

Doctorr
08-24-2003, 03:14 AM
Just bought 50 of the little b*ggers off ebay, for the footwell project......

12,000mcd.......SHOULD be bright enough......

Not very good with the cut&paste stuff, but the item # was 2550748679......also explains why I bought 50, when the lot size was 25......hit the 'buy now' button twice!.....DOH!
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doc

TerenceT
08-24-2003, 03:21 AM
the one you bought are very very bright!!

and focus too, only 6 degree

you'll be able to see if you date shave her legs!!! thru her panty hose!!1

Doctorr
08-24-2003, 03:26 AM
I think your math is fine - 330 Ohms will be perfect.

You should consider bundling a few together, since they are so small, and the mirror is a long way from the ground.....

Keep us posted!
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doc