I have the following setup:
simulate this circuit – Schematic created using CircuitLab
(The LEDs are actually some generic UV leds without a known part number, so I didn't edit the default number in the schematic.)
When applying 5 to 10 Volts at V1 I always only get D1 to glow, how can that be and what can I do to fix this?
Already checked the board for shorts and also supplied 5V directly to some other LEDs by crocodile clip cable, then they work correctly.
Oh and sometimes when using crocodile clip cable to jump over R1 some other LEDs randomly flash on, and then instantly off, and D1 remains the only one glowing.
Best Answer
If the LEDs are fully within the UV spectrum, you won't see any visible light emitted from them, except for cases where the LED is being overdriven with too much current, etc.
If these are "blacklight" LEDs then they're a deep purple with some UV, and you should be able to see visible light from them.
Assuming that these are typical 20mA If LEDs with a Vf of ~3.2 volts, you could try connecting just one of them in series with a 90Ω resistor (100Ω is the closest common value). Do this for all of your LEDs to ensure that they work.
Once you've established that they are all functional, you can go back to your series-parallel circuit. However three LEDs in series will require 3 \$\cdot\$ 3.2V = 9.6V. This means you'll need to provide at least 9.6V prior to selecting current-limiting resistors for each branch.
If you want to use 5V, consider connecting the LEDs in parallel such that they each have a 90-100Ω current-limiting resistor.
Remove R1, the 150Ω resistor from the battery to ground; it serves no purpose.