my echo hatch photoshoot

[taKuto]

Originally Posted by PK198105

yeah thats what i was thinking , however i hope your resistors are 1Watt , you're pulling about 720mW in each branch. Also the fist LEDs to go will be the ones right after you resistor which will disconnect all the other ones.

how did you calculate that? Assuming resistor is 18 ohms (most likely higher),
P = I^2 * R
P = 0.06A * 0.06A * 18 = 0.0648 W = 64.8mW
64.8mW is burned through the resistor itself.

Don't worry about checking my work, i'm not studying electrical engineering for nothing. Everything electrical i've got no problems with, it's when it comes to the mechanical stuff I'm no good with

[HTM Yaris]

All this means crap to me . Just tell me what the photon output is ...........

[taKuto]

Originally Posted by PK198105

well , you want to have a constant 60mA right? Remember Ohms law V=IR right? then 12V divided by 60mA equals 200Ohms. Now for the power you can use like you said I^2R or V X I. 60mA^2 X 200Ohms = 0.72Watt

If you use an 18ohm resistor you only dropping 1.08V

200ohms is calculated for a fixed resistor burning all that current (so no LED's in that circuit, just a resistor alone). The way you can factor in LED's is that you need to subtract all the forward voltage drops and resistor handles the leftover voltage. If you want to look at it that way, assume the LED's were dropping 3.5V at 60mA (these specific ones are not dropping that exact value, but let's assume anyways).

V = 12 - 3.5 - 3.5 - 3.5 = 1.5V. This is the leftover voltage you will use a resistor to deal with. So V/I = R, 1.5V / 0.06A = 25 ohms. So 3 LED's + 25 ohms for that circuit.

Since LED's are a function of current, I usually will use an ammeter and potentiometer to dial in the desired current. China LED's don't have nice and pretty voltage to current charts to work with, and their bins are always different, so it's always a guess and check.

[taKuto]

The voltage drops are still pretty average for a white LED (3.4-3.8V typical), it's current that usually varies. I got the LED's off some random china supplier from ebay. 10mm 5 chip white LED's i think.

[taKuto]

yup, but china stuff is still much cheaper :)
only things i've been browsing on digikey are the offerings from cree. I might pickup some P4's to play with. The higher powered offerings from cree are far too expensive off digikey, i'd rather get them from china suppliers such as dealextreme.

[taKuto]

I was going for digital/analog hardware but changed focus to power systems

[taKuto]

university of toronto

[yaris-me]

Originally Posted by taKuto

university of toronto

[Doc Zaius]

Hahhaha... j/k. Whatever. Nice pics, taKuto. Nice cutoff too... *is* it a kit? Or a retro?

[red_rims]

sick

[taKuto]

TL projectors with philips ultinons running off hella gen 3 ballasts. OEM purple power!

mastaofdisasta, just basic circuit theory, time for you to brush up! :)