Hi wonder if any of you lovely people can help ?
I have just put together an audio amplifier . The case has an LED indicator lamp on the front panel which is way to bright at the moment . The led is white and has a operating voltage of 3.2-3.8 V . I measure 2.6v to where it’s connected to. I’m guessing I need a resistor in series and wondered what value and wattage I might need to bring it down to a gentle glow ?
Many thanks in advance ...
I have just put together an audio amplifier . The case has an LED indicator lamp on the front panel which is way to bright at the moment . The led is white and has a operating voltage of 3.2-3.8 V . I measure 2.6v to where it’s connected to. I’m guessing I need a resistor in series and wondered what value and wattage I might need to bring it down to a gentle glow ?
Many thanks in advance ...
Do you have a resistor in-circuit at the moment, across which you measured your 2.6V? You could try a 2k7 resistor in place of what you have right now, this should give a fairly gentle glow. I'm assuming you've a ~6V supply which is powering the LED.
The wattage in the resistor will be so low anything will do the job (even down to an 0402 SMT one).
The wattage in the resistor will be so low anything will do the job (even down to an 0402 SMT one).
The wattage is minimal. 1/4 or 1/2Watt is adequate.
Reducing the current reduces the brightness. It has little to do with the voltage available.
I would, if I had no idea of the supply voltage, use a 22k pot and measure the value of the resistance at the desired brightness. You could of course place an LDR in series with the LED feed resistor, that will make it brighter in the light and darker in the low light of a listening room. Just a thought.
Reducing the current reduces the brightness. It has little to do with the voltage available.
I would, if I had no idea of the supply voltage, use a 22k pot and measure the value of the resistance at the desired brightness. You could of course place an LDR in series with the LED feed resistor, that will make it brighter in the light and darker in the low light of a listening room. Just a thought.
Thanks for your replies . The led is connected to a GV-sub01 LPF circuit ( from China) The circuit is powered by a 12v-0V-12v power supply. I’m a bit rusty on resistor values but it’s 4.7k ( Yellow,Violet,Black,Brown) In series at the moment .
What I mean by a faint glow is that you can see it’s on but not distracting and comfortable for home cinema use.
I like the idea of the LDR but nowhere to mount one now really !
Hope the extra info makes it easier to work out
Thanks
What I mean by a faint glow is that you can see it’s on but not distracting and comfortable for home cinema use.
I like the idea of the LDR but nowhere to mount one now really !
Hope the extra info makes it easier to work out
Thanks
Well not having many components to hand these days I managed to cobble together 2 x 10k and one 47k resistor . Tried each value and the two 10ks together and added the 47k in series too . It’s a big improvement but I’m thinking 100k would be nearer the mark. Seems a lot on top of what you guys recommend?
it's not too much as long as it works.
I routinely run around the same series resistance on LEDs, the modern high brightness types sure can be very bright even at very small currents.
I routinely run around the same series resistance on LEDs, the modern high brightness types sure can be very bright even at very small currents.
Ultrabright blue LEDs I use a 100k dropping resistor from 12V. It's remarkable how bright an LED is even with it's drawing only a few microamperes.
That LED was designed to scream "Look At Me!!" in a bright sunny showroom.
Now that you already seen it, in dim household light you may want 1/10 or even 1/100 as much current. Yeah, just keep upping the resistor.
At "some" point it will just go dead dark. Back in 1980 the leakage was so bad we didn't get much at 1/10th rated current. Modern stuff is much better and the linear range goes much lower. And worst can happen, you back-off from the value that leaves the LED "dark".
Now that you already seen it, in dim household light you may want 1/10 or even 1/100 as much current. Yeah, just keep upping the resistor.
At "some" point it will just go dead dark. Back in 1980 the leakage was so bad we didn't get much at 1/10th rated current. Modern stuff is much better and the linear range goes much lower. And worst can happen, you back-off from the value that leaves the LED "dark".
Some audiophile gear used to have a "lights off" switch that makes it possible listening to the music, not to the light show.
The appearance of LED dimming can be done by flashing, but that can create other problems especially in audio gear. Why flash when a simple resistor will do the job?
Why complicate things with a timer circuit? Kiss principal (keep it simple stupid.) a resistor is cheaper than a 555 isn't it?
On my TV there is an annoying LED right below the screen to tell you if it's in standby (red)....ok....when you turn it on it turns bright blue..effin' fantastic idea! Stuck a bit of black insulation tape over it, perfect, it's just about visible which is handy as I can tell my remote has worked when I turn it on 🙄
In days of old a light meant 'on'. Now it means 'off', but powered.
'Red' used to mean neon - it was about the only colour they could do.
Then 'red' meant something is wrong, you need to stop what you are doing.
Now 'red' means everything is fine, and the device awaits your command.
I am getting old!
'Red' used to mean neon - it was about the only colour they could do.
Then 'red' meant something is wrong, you need to stop what you are doing.
Now 'red' means everything is fine, and the device awaits your command.
I am getting old!
Because sometimes a resistor won't do. That's especially the case with white and blue LEDs.
You can run a 555 timer above the audio range if you're concerned about the switching frequency getting into your sensitive audio circuits. Another possibility is to pay attention to the layout (of the 555 and the audio circuit) to minimize the coupling between the two.
Yeah, you gotta love the ON indicators. A friend of mine had a laptop (Dell, I think) with a bright blue LED in the power button. It was blinding when you tried to use the machine in a normally lit living room at night. I much prefer Apple's approach of turning off the standby indicator when the equipment is in use (and its screen is providing plenty of indication of this).
Tom
Normally on bright leds the front surface is polished, You can try to sand it a bit to diffuse more the light.