Hi all,
I recently bought some neat little LED pinspots that use 3 AG10 (3 X 1.5VDC) button cell batteries to power a single LED. The AG10's aren't going to last very long so I decided to mod the lights to use 9 volt batteries; longer-lasting and easier to change. Using an online LED resistor calculator, I installed 220 ohm resistors in the lights. I used the following values:
Source voltage = 9VDC
FV = 3.4VDC
FC = 30mA
These are nominal values - I don't have actual specs for the LEDs.
However, I notice that the LEDs are now running ~75% of the brightness that I get from using the AG10 batteries. Reducing the value of the resistor (150 ohm) doesn't change this, not surprisingly. There is no resistor used in the lights. If I use a straight 4.5VDC power source, such as 3AAA batteries, I get the full brightness again. I'd like to get the full brightness using the 9 volt battery. What am I missing here?
I recently bought some neat little LED pinspots that use 3 AG10 (3 X 1.5VDC) button cell batteries to power a single LED. The AG10's aren't going to last very long so I decided to mod the lights to use 9 volt batteries; longer-lasting and easier to change. Using an online LED resistor calculator, I installed 220 ohm resistors in the lights. I used the following values:
Source voltage = 9VDC
FV = 3.4VDC
FC = 30mA
These are nominal values - I don't have actual specs for the LEDs.
However, I notice that the LEDs are now running ~75% of the brightness that I get from using the AG10 batteries. Reducing the value of the resistor (150 ohm) doesn't change this, not surprisingly. There is no resistor used in the lights. If I use a straight 4.5VDC power source, such as 3AAA batteries, I get the full brightness again. I'd like to get the full brightness using the 9 volt battery. What am I missing here?