Driver for 2 led's

Other Hardware Motors, Mechanics, Power and CNC
1

Hey ya'll!

I have been hesitating to post because I have found some similar posts but I believe my situation may be a little different.

I am trying to power two separate LED's, both similar to THIS LED. In short, it's a 3V 150mA LED.

Only one of the LED's will be on at a time (because they're two different colors), but I want to power it with my little 3V arduino trinket running off two 18650 batteries (seen below).

Can I solely use a 74HC595 to do this?

I am trying to make a small flashlight for some research project.

How can I drive the LED's properly without burning up my board or the diodes?

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3

Drive LEDs with transistors, use the 18650 4.5V with series resistor as supply.

4

larryd:
Drive LEDs with transistors, use the 18650 4.5V with series resistor as supply.

Wouldn't that cause issues with current after the diode has been running a while? Wouldn't it also heat up quite a bit?

5

You would be responsible for heat sinking the LED.

3V X .150A = 450mW

6

larryd:
You would be responsible for heat sinking the LED.

3V X .150A = 450mW

Wow -- OK, much easier than I thought. Like the Tip 120 or BC547? I just don't know what to expect for <0.5W in terms of thermal discharge

7

TIP120 has a VCE(sat) of ~2v so it would be a poor choice.
BC547 does not have the power capacity.

You need a MOSFET that turns on with 3v.
IRLZ44 should fit this requirement.

Is your Trinket 3v or 5v?

8

Thank you! That really gave me a boost on this project.