It can be used a light bulb + LDR in DOD 280 compressor?

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gigelmargel
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Post by gigelmargel »

Hello all!
I've finished a DOD 280 compressor clone using this layout: http://tagboardeffects.blogspot.com/201 ... essor.html.
I tried a couple of VTLs and LED+LDR combinations and I like almost all due to their different flavors :D
After that, I tried to use a 1.5V/50mA light bulb with a LDR, but it didn't work: the light bulb didn't light at all (but it's working - I've tested before and after).
Maybe the current it's too low for it? I used 2n4401 transistors and LM358.

Maybe I need to use a higher voltage? Looking at the schematic, it's seems to be OK to increase the voltage to 18V, but I think I must increase the limiting resistor in series with the VTL/LED.

As far as I know, EHX White Finger has a switch between LED and light bulb, so it's possible :hmmm:

Thank you all!
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plush
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Post by plush »

gigelmargel wrote: Maybe I need to use a higher voltage?
You should experiment with decreasing current limiting resistor value.

Refer to Ohm's law.
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gigelmargel
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Post by gigelmargel »

plush wrote:
gigelmargel wrote: Maybe I need to use a higher voltage?
You should experiment with decreasing current limiting resistor value.

Refer to Ohm's law.
Good ideea...thx!
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gigelmargel
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Post by gigelmargel »

gigelmargel wrote:
plush wrote:
gigelmargel wrote: Maybe I need to use a higher voltage?
You should experiment with decreasing current limiting resistor value.

Refer to Ohm's law.
Good idea...thx!
I've put a 10K linear pot in place of the limiting resistor value, but light bulb don't want to light at all :cry:
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plush
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Post by plush »

gigelmargel wrote:
gigelmargel wrote:
plush wrote:
gigelmargel wrote: Maybe I need to use a higher voltage?
You should experiment with decreasing current limiting resistor value.

Refer to Ohm's law.
Good idea...thx!
I've put a 10K linear pot in place of the limiting resistor value, but light bulb don't want to light at all :cry:
Maybe it simply has no time to light up. Compressors are usually pretty fast, while it may take ut to couple hundred milliseconds for a classic filament lightbulb to light up.
Also 10k pot is too large to dial. Actual resistance needed can be somewhere in between 100-300 Ohms.
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lolbou
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Post by lolbou »

Check a Univibe schem and add a driver transistor to handle much current... Don't think it can handle high frequencies because the filament glow has some kind of inertia (escpecially if the rise/fall time of LDRs is long)...
- Are you a mod or a rocker?
- Uh, no, I'm a mocker.
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gigelmargel
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Post by gigelmargel »

plush wrote:
gigelmargel wrote:
gigelmargel wrote:
plush wrote:
gigelmargel wrote: Maybe I need to use a higher voltage?
You should experiment with decreasing current limiting resistor value.

Refer to Ohm's law.
Good idea...thx!
I've put a 10K linear pot in place of the limiting resistor value, but light bulb don't want to light at all :cry:
Maybe it simply has no time to light up. Compressors are usually pretty fast, while it may take ut to couple hundred milliseconds for a classic filament lightbulb to light up.
Also 10k pot is too large to dial. Actual resistance needed can be somewhere in between 100-300 Ohms.
Thank you, plush! Even with the resistance at 0, the lightbulb don't want to light up :)
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gigelmargel
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Post by gigelmargel »

lolbou wrote:Check a Univibe schem and add a driver transistor to handle much current... Don't think it can handle high frequencies because the filament glow has some kind of inertia (escpecially if the rise/fall time of LDRs is long)...
Thank you, lolbou! I thought about that, but I don't have enough knowledges...I will read much about it :D
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bridgettekarishma
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Post by bridgettekarishma »

If you put a 10K linear pot in place of the limiting resistor value, the light bulb will never light, there is nothing to be surprised about. You can replace them with wifi light bulbs or similar, but you need to check the output current and install a current-limiting resistor if you plan to use LEDs. If you suddenly do not know the three laws (rules) of Kirchhoff for electric circuits use Ohm's law I = U/R, then calculate the resistance and already proceed from the desired parameters. The output characteristics of the current and voltage at the point of connection may also be different, note them down when replacing the lamp later
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Post by andregarcia57 »

I built this pedal and I really liked the result

LDR 5528 + green diffused LED 5mm.

http://dirtboxlayouts.blogspot.com/2023 ... r-280.html
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