Maker Pro
Maker Pro

Blue LEDs

J

Jimmie D

Jan 1, 1970
0
I have a few blue LEDs I want to use on a project. The LEDs operate at 5
volts nd my project also operates a 5 volts. Do I need a current limiting
resistor in series with the LED.


Jimmie
 
U

UCLAN

Jan 1, 1970
0
Jimmie said:
I have a few blue LEDs I want to use on a project. The LEDs operate at 5
volts nd my project also operates a 5 volts. Do I need a current limiting
resistor in series with the LED.

Some LEDs have a current limiting resistor built in. Most don't. I would
measure the forward drop with an ohmmeter if I were you. If no current
limiting resistor is built in, add one. Helps to know the part number.
If you are unsure, start with a 1K variable resistor. Decrease it slowly
until the LED reaches your desired brightness. Measure what value of
resistance you had, and use the closest value to that.
 
A

Arfa Daily

Jan 1, 1970
0
UCLAN said:
Some LEDs have a current limiting resistor built in. Most don't. I would
measure the forward drop with an ohmmeter if I were you. If no current
limiting resistor is built in, add one. Helps to know the part number.
If you are unsure, start with a 1K variable resistor. Decrease it slowly
until the LED reaches your desired brightness. Measure what value of
resistance you had, and use the closest value to that.

All valid advice. I would add, measure the current at the same time. For
most blue LEDs, as a general rule of thumb, don't exceed a forward current
of 25 - 30 mA. The lower you can keep the current to get the brightness you
need, the better when you are using DC rather than pulse drive. A lower
forward current can extend the 50% life by several times.

Arfa
 
W

William Sommerwerck

Jan 1, 1970
0
I agree with UCLAN. Stick a 1K resistor in series with the LED and see what
happens when you apply 5V to it.
 

Similar threads

Top