Author Options:

How to UV-modify the "USB fading star" instructable? Answered

I have built sooraj619's "USB fading star"  circuit (https://www.instructables.com/id/USB-fading-star/), but with UV LED's instead of red. I hadn't thought about the fact that red LED's have a quite low voltage need (about 1,8-2 volts) compared to UV LED's (3.2v – 3.8v). But it is a problem. The UV LED's (24 pcs) aren't even close to full light intensity. They do, on the other hand, pulse in the right slow way.

Does anyone know in which way the circuit could be changed to make the LED's light up properly without the LED pulsing being all disturbed? The circuit input voltage should remain 9 volts though.


Can't you just remove the variable resistor? Or place a low OHM resistor in its place?

Thanks for the answer Awesome-aniac.

I have just tried replacing the var. resistor with wire, but the result isn't so good. When the input voltage is at 9 volts, the LED's just light up constantly - no pulsing. Not at the highest intensity either.
It is actually the same happening when you turn the var. resistor to the lowest Ohm level; the LED's light up constantly. I think perhaps the 100uf 16v electrolytic capacitor gets charged to quickly. Perhaps replacing the 33K resistor connected to pin 3 with another would change it? I'm pretty lost.

It lights up more than the individual LED's when they are all connected. But it still isn't at full intensity + i need all 24 LED's.
Is there another way?