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### 7.95

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 quantity In stock 39 in stock 7.95 1+ units 7.16 10+ units 6.36 100+ units

### Skills

Description: We all know that you can never get too many LEDs. Don't worry, we've got you covered. This is a pack of 25 LEDs all conveniently packaged in a nice reusable ESD safe bag. Make that next project shine!

Features:

• 25 violet LEDs

• Standard size - T1 3/4 5mm
• 180 mcd brightness
• 3.2V forward drop
• Max current 20mA

Documents:

• It would be really nice if you could list the LED light frequency, in nm, like you have done for the new IR LED bag. Color names can be pretty vague.
If you have trouble getting to the tutorial (http://tiny.cc/r0SEG), make sure the URL is entered exactly as shown (it’s very picky about upper/lower case).

• Agreed… The wavelength would be good to list. Maybe even a datasheet? :-P

• I agree with previous comments,
What is the exact light frequency ? is it just violet or also ultrviolet ?

• How bout a pic of an led shining so we can see the color?

• It’s kind of a blueish red, or reddish blue color. Just kidding. We’ll get a shot of it up. It tends more towards blue. A pale reddish blue is the best description. We should have a picture up by next week.

• One can calculate in the other direction:
I = Vres/Rres = (Vsupply-Vled)/Rres
So for a 150 ohm resistor, at 6 V supply:
I = (6 V - 3.2 V)/150 ohm = 18.7 mA
at 4.8 V supply:
I = (4.8 V - 3.2 V)/150 ohm = 10.7 mA (about half the capability of the LED in this case.
I suggest the current “Resistor Value: 150 ohm” be deleted and “Rres = (Vsupply-Vled)/Iled” be provided, along with an example or two (6 V and 4.8 V come to mind).
On a related note: It would be helpful to have a link to the datasheet for the LEDs.
Eric

• I think the “Resistor Value: 150 ohm” statement is counterproductive.
Firstly, the packaging also states a current of 20 mA, a Vdrop of 3.2 V, and Ohm’s Law. But:
R = V / I = 3.2 V / 0.02 A = 160 ohm
If you assume that the “Resistor Value” was meant to be the resistance of the required current-limiting resistor, then the value given (or any other value) is not generally valid. In the general case:
The voltage to be dropped across the resistor:
By Kirkhoff’s voltage law: Vres = Vsupply - Vled
By Ohm’s Law, Rres = Vres / Ires
By Kirkhoff’s current law: Ires = Iled
Combining these give us:
Rres = Vres/Ires = Vres/Iled = (Vsupply - Vled)/Iled
Although Vled and Iled are specified (3.2 V and 0.02 A, respectively), Vsupply depends on how these LEDs are to be powered. The package insert shows “AA battery four pack”. Nominally, 4 alkaline cells in series provide 6 V, so:
Rres = (Vsupply-Vled)/Iled = (6 V-3.2 V)/0.02 A = 140 ohm
However, nominally 4 NiMH cells in series provide 4.8 V, so:
Rres = (Vsupply-Vled)/Iled = (4.8 V-3.2 V)/0.02 A = 80 ohm
[To be continued…]

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