Led indicaror resistor in fuzz face

DocBrown · February 11, 2020, 11:46:33 AM

Hello gentlemen.

My fuzz face sounds great after a few tweaks. I'm still a noob, but I've build my first sucessfull pedal and this is great. I plan to make a few improvement and first of all, add a led indicator.

I have a super bright 5mm aqua blue led that I plan to use, solder between the +9V on the PCB and the ground on the switch. I know I must add a resistor to avoid to blow the led, but what resistor value should I use ?

Thanks a lot !

italianguy63 · February 11, 2020, 11:58:14 AM

I usually use a 2K2. But, with a super-bright prolly a 4K7

MC

intripped · February 11, 2020, 12:10:56 PM

Don't be afraid to increase the value, I've used also10k with superbright LEDs. They could be blinding in darkness.
best thing to do is trying different values on breadboard.

davent · February 11, 2020, 12:15:06 PM

I've gone all the way to 47k with 9v and a super bright. Breadboard a bunch of values with the led before soldering up the best value for your particular LED.
dave

DocBrown · February 11, 2020, 12:32:25 PM

Thanks. I'll experiment but I'd like to know the minimum value to avoid blowing the led...

davent · February 11, 2020, 12:53:58 PM

You may find a super bright is bright enough running on 1mA (.001A) or less, i think max rating is often around 20mA (?). The resistor will drop 6-7.2, 7.3v or so with a 9v source. Ohms law, V=IR says 350r would give you 20ma with a 7v drop across the resistor. 20mA & a super bright is blinding and probably the largest power usage in the pedal.

I've been away for awhile i think, i've got that right.
dave

DocBrown · February 11, 2020, 01:06:50 PM

OK thanks a lot. I'll try to preserve my eyes!

DocBrown · February 11, 2020, 01:45:27 PM

I just ordered 10k, to 100k resistors with 10k steps to experiment. I should find the correct value in there. Thanks a lot.

PRR · February 11, 2020, 05:17:10 PM

330 Ohms is "safe for the LED" but probably not for your eyes.

"SuperBrite" on a dark stage, you might go 100X higher. (There's no real point paying more for SuperBrite in this work, but use what you have.)

DocBrown · February 11, 2020, 05:43:31 PM

Thanks, I'll stay on standard led next time.

bamslam69 · February 11, 2020, 05:48:17 PM

Those LED's are hilariously bright. You can almost turn the lights off in the room. Lately, I run over them with some steel wool or sandpaper to diffuse them a bit.

I just grab a resistor which I have heaps of around the 2k mark, without giving much thought.

GibsonGM · February 11, 2020, 05:52:39 PM

I've used 1k on those supa-brights, no testing. 9mA then. WAY WAY too bright, ha ha ha! My band mates made me put tape over it on stage til I could up the value. I still have a bunch of stuff from the 80s, 90s, where you would really try to limit how much power it's using, you might make it to 1k with them, but these things are INSANELY bright.

Point being, if you wanna play, go ahead and grab 1k, and go up from there, totally safe, as is 330R previously mentioned (but wear shades!). 3.3k has been a good one, 4.7k too.

DocBrown · February 11, 2020, 06:12:15 PM

Yes! I've found in my stock a standard blue. I've read that 1k should be fine and it will save my eyes.

Anyway I've learned a lot tonight so thank you all.

willienillie · February 11, 2020, 07:59:40 PM

I've got one of those clear-off/green-on uber-brights that is still too bright IMO with a 100k CLR. I usually use these diffused reds with a 47k though:

https://www.taydaelectronics.com/leds/round-leds/5mm-leds/led-5mm-red.html

Obviously I don't like very bright LEDs. And a fraction of a mA is good for battery life, where applicable.

amptramp · February 12, 2020, 09:19:26 AM

There is another way to get the brightness you need for every ambient lighting environment: Use a CdS or CdSe photoresistive cell to set the brightness. You may need a resistor in series to limit brightness and you may need one in parallel to get a usable minimum brightness setting but once you have done this, you are set for all ambients whether it is an outdoor stadium in daylight or a black nightclub room at night.

You might want something other than CdS or CdSe if ROHS is important to you. ROHS (Reduction of Hazardous Substances) restricts the use of lead, cadmium and mercury among other things and is a requirement if you intend to sell your units in certain parts of the world.

DocBrown · February 12, 2020, 10:59:20 AM

I'll keep that excellent idea, thank you !

dennism · February 12, 2020, 03:46:11 PM

Since you're Doc Brown, shouldn't you at least be considering using a flux capacitor for this job? Asking for a friend.

DocBrown · February 12, 2020, 04:14:34 PM

Well I'm pleased you ask this question. It could be a possibility but I can't get 2.21 gigowatts from a 9v battery. Plus, 88mph is way too fast for a Fuzz face. Maybe on next build?

Rob Strand · February 12, 2020, 04:36:34 PM

QuoteThere is another way to get the brightness you need for every ambient lighting environment: Use a CdS or CdSe photoresistive cell to set the brightness. You may need a resistor in series to limit brightness and you may need one in parallel to get a usable minimum brightness setting but once you have done this, you are set for all ambients whether it is an outdoor stadium in daylight or a black nightclub room at night.

You might want something other than CdS or CdSe if ROHS is important to you. ROHS (Reduction of Hazardous Substances) restricts the use of lead, cadmium and mercury among other things and is a requirement if you intend to sell your units in certain parts of the world.

You can use the LED itself as a light sensor but the circuit might be more complicated than the pedal

.

I prefer the LED current to be low as possible. It is hard to find a balance like some Routers light-up the room at night but are hard to see in bright light. My last Modem has very bright LEDs but has a door to cover them over - seems extreme but in practice it's a very good idea.

amptramp · February 12, 2020, 06:35:42 PM

Quote from: Rob Strand on February 12, 2020, 04:36:34 PM
QuoteThere is another way to get the brightness you need for every ambient lighting environment: Use a CdS or CdSe photoresistive cell to set the brightness. You may need a resistor in series to limit brightness and you may need one in parallel to get a usable minimum brightness setting but once you have done this, you are set for all ambients whether it is an outdoor stadium in daylight or a black nightclub room at night.

You might want something other than CdS or CdSe if ROHS is important to you. ROHS (Reduction of Hazardous Substances) restricts the use of lead, cadmium and mercury among other things and is a requirement if you intend to sell your units in certain parts of the world.

You can use the LED itself as a light sensor but the circuit might be more complicated than the pedal .

I prefer the LED current to be low as possible. It is hard to find a balance like some Routers light-up the room at night but are hard to see in bright light. My last Modem has very bright LEDs but has a door to cover them over - seems extreme but in practice it's a very good idea.

You could use a phototransistor to set the LED current and it wouldn't be all that much more of a problem than a CdS or CdSe photocell. You don't need base drive but you will still need the series resistor to set the maximum light and a shunt resistor to set the minimum light and not much more circuitry than that.

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Led indicaror resistor in fuzz face