I'm planning on having a set of blue LEDs connected in series. I'm looking at having about 30-40 LEDs in series. The power supply will be from a USB 2.0 port mounted on my television. Reading up on the specs for USB 2.0 it has a pin for 5v and ground.
If I used this as my power supply, will my LEDs light up as much as they should or would they be really dim.
The specs for the LEDs are:
- Material : Semiconductor; Light Color: Blue
- Head Dia.: 5mm / 0.197"; Forward Voltage: 3.2-3.4V
- Luminous Intensity: 2000-3000MCD; Wave Length: 460-463
- Size: 24 x 3mm / 0.9" x 0.1"(L*W); Package Content: 50 x Light
Emitting Diode
And a link to amazon where I purchased is this
Best Answer
They definitely won't work from USB if connected in series (even two LEDs in series won't work).
If you connect a ~100 ohm resistor in series with each LED, you may be able to run about five LED/resistor sets connected in parallel from a USB port. Without negotiation, a USB port is only guaranteed to supply up to 100 mA (although many USB ports have no current control, and may supply 500 mA or more).
According to the comments on Amazon, there is no recommended maximum current data for these LEDs, so I'm guessing 20 mA per LED would be acceptable.