Well yet again I feel dumb as heck... how to light an LED for crying out loud !??
So let's start with the LED, a Luxeon Rebel Star.
Typical Forward voltage is 3.2v.
I intend to run it at 2 current levels, 350ma & 700ma.
Proposed power source will be 3*AAA rechageable cells = 3.6v.
Here's my calcs for the resistor when running at 350ma:
(3.6v-3.2v)=.4v
0.4v / .350 = 1.1 Ohm
and 0.6Ohm to produce 700mA
Can someone firstly tell me if that's right ?
tbh I feel silly putting such a small resistor.... but I'm inexperienced and easily paranoid !
Next problem....erm 'challenge'
I want to then control the brightness of this LED with PWM from an ATTiny.
Now that will involve a transistor.
I am completely lost as to how to choose the best transistor for this.
Mosfets, as I understand, would be overkill and possibly need a driver ??
So I'm sticking on the line of transistors.....
I found this one : TIP31C
From what I can tell, it will handle the current/voltages that I need, but I'd really be grateful of a second opinion !
http://www.hobbytronics.co.uk/tip31c
Thank you for any advice
So let's start with the LED, a Luxeon Rebel Star.
Typical Forward voltage is 3.2v.
I intend to run it at 2 current levels, 350ma & 700ma.
Proposed power source will be 3*AAA rechageable cells = 3.6v.
Here's my calcs for the resistor when running at 350ma:
(3.6v-3.2v)=.4v
0.4v / .350 = 1.1 Ohm
and 0.6Ohm to produce 700mA
Can someone firstly tell me if that's right ?
tbh I feel silly putting such a small resistor.... but I'm inexperienced and easily paranoid !
Next problem....erm 'challenge'
I want to then control the brightness of this LED with PWM from an ATTiny.
Now that will involve a transistor.
I am completely lost as to how to choose the best transistor for this.
Mosfets, as I understand, would be overkill and possibly need a driver ??
So I'm sticking on the line of transistors.....
I found this one : TIP31C
From what I can tell, it will handle the current/voltages that I need, but I'd really be grateful of a second opinion !
http://www.hobbytronics.co.uk/tip31c
Thank you for any advice