Suggestions for right battery sources for Reverse mount LEDs in a small PCB

Thread Starter


Joined Oct 12, 2023

I'm working on the 10mm x 8 mm PCB board to design the above circuit .

Here are the LED specs
Green LED -
Yellow LED -
Blue LED -

Please suggest any right battery source to power up the LEDs with max brightness , as these are reverse mount LEDs. Light needs to penetrate the PCB.


Joined Aug 31, 2022
It would help if you posted the data sheet information as links instead of text. Without checking them, the main thing to know about LEDs is that the knee voltage, and therefore the voltage across them varies according to colour, for example red is around 1.8 volts whilst blue is around twice that. And that voltage drop doesn’t change much with current

You should look at the specifications which will probably tell you the voltage drop and the maximum current and use ohm’s law to select a suitable resistor such that it limits the current to whatever you choose.

For example, suppose you have a 12V power supply, the voltage across your LED is 2V and you want the current to be 20mA then you need the resistor to drop 10V at 20mA so R = V/I = 10/20 x 1000 = 500R. For a 5V supply it would be 3/20 x 1000 so 150R

In other words, the supply voltage is not critical but the series resistor should be selected to limit the current