LED circuit; do I need a resistor?

[Sunil Mansoor]

First of all, I have 0 electrical knowledge. Got some basics from YouTube
The led I wanna use needs 3 - 3.6v and 350mA.

I am planning to use 3 AAA batteries (1.5v x 3 = 4.5v), because that’s the battery case size that fits into the space.
I have calculated the resistance (hopefully correctly)
R = (4.5v - 3.5v) / 0.35 = 2.85 ohm

Q1. The resistance needed seems very small to all the examples I’ve come across. Do I need a resistor? If so, is there anything else I need to know to pick the correct resistor?

Q2. I’ve noticed different AAAs have different mAh. What does it mean and how does it relate to the led’s 350mA current requirement?

 

[gophert]

The LED may have any value in the specified range. Your calculation method is correct but you should repeat the calculation with the LED forward voltage = 3.0V as well. Then use the largest resistance of the two calculated extremes.

 

[KeepItSimpleStupid]

The AA battery won't last very long: https://www.mouser.com/datasheet/2/490/MN15US11191-1878803.pdf
and it does not appear suitable. The 100 mA constant discharge line is really quick.

 

[audioguru]

AAA batteries are much smaller than the AA battery shown so they will show the LED dimming for an hour until the the voltage is too low to light them.
Also, mAh is usually used for rechargeable batteries and when the voltage has dropped to only 0.8V per cell which is less than the LED needs.

 

[alec_t]

It is not good practice to run components at their maximum rated current if you want them to have a long and happy life. I'd suggest 300mA (or less) for that LED. The brightness difference won't be really noticeable by eye.

 

[Pommie]

Another thing to consider is heatsinking. A 1W LED without a heatsink will get very hot and may burn out. Do you have a link to the actual device?

Mike.