Simple, chaotic, slow LFO based on weird LEDs
Aug 8, 2023 12:00:50 GMT
pol, rockysmalls, and 5 more like this
Post by keurslagerkurt on Aug 8, 2023 12:00:50 GMT
Hey all!
Been experimenting with some 'auto colorchanging LEDs' from AliExpress, these ones: www.aliexpress.com/item/32950189409.html
I can't seem to find them from a 'legit' brand/dealer, so there is basically no information nor datasheet on them. But, from my testing, they seem to have a small IC incorporated in the package. This IC changes the LED color by sending different current through it, and fades between different colors by quickly toggling (PWM style) between the colors.
So if we convert this fluctuating/changing current into a voltage, we basically have a CV source. However, when using only one LED, this is a pretty 'boring' CV source. Sure it is a weird LFO, but you cannot change the rate or shape. However, when we add a second LED in parallel, the current starts to fluctuate in a very chaotic way! It depends on when exactly you add the LED, and each LED is a little different as well, delivering completely different CV depending on these small differences.
A small demo using 1 -> 3 LEDs in parallel, controlling the WASP filter cutoff (Solina is sound source):
So in the demo I use two different types of LEDs, two slowly fading LEDs, and in the end one quicker LED. Pretty neat imo! And the best news is that the circuit is quite easy. You can find it below. Basically, R1 is used to convert the current into a voltage. In fact, you could already stop the circuit here and experiment with using this signal! However, you will notice that it needs some extra amplification, and maybe some filtering to filter out the PWM signal of the IC inside the LED. So this is added in the stages afterwards: buffering, a gain/amp stage, and a simple filter.
For those interested, I have some scope images as well. Yellow trace is the output of the complete circuit, blue trace is the signal at the top of R1 (so not amplified, not filtered).
for three slow LEDs in parallel:
For one slow and one fast LED in parallel:
Had great fun playing with this, hopefully it is of use to someone!
Cheers
Zeno/Kurt
Been experimenting with some 'auto colorchanging LEDs' from AliExpress, these ones: www.aliexpress.com/item/32950189409.html
I can't seem to find them from a 'legit' brand/dealer, so there is basically no information nor datasheet on them. But, from my testing, they seem to have a small IC incorporated in the package. This IC changes the LED color by sending different current through it, and fades between different colors by quickly toggling (PWM style) between the colors.
So if we convert this fluctuating/changing current into a voltage, we basically have a CV source. However, when using only one LED, this is a pretty 'boring' CV source. Sure it is a weird LFO, but you cannot change the rate or shape. However, when we add a second LED in parallel, the current starts to fluctuate in a very chaotic way! It depends on when exactly you add the LED, and each LED is a little different as well, delivering completely different CV depending on these small differences.
A small demo using 1 -> 3 LEDs in parallel, controlling the WASP filter cutoff (Solina is sound source):
So in the demo I use two different types of LEDs, two slowly fading LEDs, and in the end one quicker LED. Pretty neat imo! And the best news is that the circuit is quite easy. You can find it below. Basically, R1 is used to convert the current into a voltage. In fact, you could already stop the circuit here and experiment with using this signal! However, you will notice that it needs some extra amplification, and maybe some filtering to filter out the PWM signal of the IC inside the LED. So this is added in the stages afterwards: buffering, a gain/amp stage, and a simple filter.
For those interested, I have some scope images as well. Yellow trace is the output of the complete circuit, blue trace is the signal at the top of R1 (so not amplified, not filtered).
for three slow LEDs in parallel:
For one slow and one fast LED in parallel:
Had great fun playing with this, hopefully it is of use to someone!
Cheers
Zeno/Kurt
