The newguy11
New Member
Hello,
I'm trying to make an efficient LED grid backlight using x16 (5mm) white leds. The leds are rated with Vf of 3.2-3.6v and a max forward current of 25 mA. I have to use 3 AA batteries (4.5v) to power the grid.
To test the brightness I wired them up in parallel without resistors. It worked fine and the light output was very good. An online calculator said I should use a resistor (39 ohms) in front of every LED. I would also like the grid to have a high low setting, possibly mid level setting. My current plan is to use a two or three way switch to control light output...My questions are...
1) can I get away (reliable use) without using resistors to get the full brightness?
2) Can I use one resistor for the whole grid? instead of one in front of each LED. how do you calculate that resistance?
3) And if #2 is possible...Is using different resistors the simple/best way to control the light level via a 2 or 3 way switch?
4) I'm I missing another simple way hooking these LED's up? I would like to use the least amounts of parts, keep it simple but reliable, and keep costs very low.
5) What kind of life can I expect, or how is the calculated. I want the low setting to last a while but I know that will depend on the resistance and mAh of the batteries. What can I expect ballpark High/Low?
thanks
I'm trying to make an efficient LED grid backlight using x16 (5mm) white leds. The leds are rated with Vf of 3.2-3.6v and a max forward current of 25 mA. I have to use 3 AA batteries (4.5v) to power the grid.
To test the brightness I wired them up in parallel without resistors. It worked fine and the light output was very good. An online calculator said I should use a resistor (39 ohms) in front of every LED. I would also like the grid to have a high low setting, possibly mid level setting. My current plan is to use a two or three way switch to control light output...My questions are...
1) can I get away (reliable use) without using resistors to get the full brightness?
2) Can I use one resistor for the whole grid? instead of one in front of each LED. how do you calculate that resistance?
3) And if #2 is possible...Is using different resistors the simple/best way to control the light level via a 2 or 3 way switch?
4) I'm I missing another simple way hooking these LED's up? I would like to use the least amounts of parts, keep it simple but reliable, and keep costs very low.
5) What kind of life can I expect, or how is the calculated. I want the low setting to last a while but I know that will depend on the resistance and mAh of the batteries. What can I expect ballpark High/Low?
thanks