Hello everyone, happy new Year!
I was thinking about bringing every LED from my amp (F4) to the front-panel.
That is, 2 from the universal PSU, 2 from the amp-channels, and (?) 2 from the speaker protection (if they light up at all) - so 2 or 3 different sources.
Brightness will be adjusted through resistors.
Will their respective brightness be the same (with the same resistors), or will they vary depending the source (PSU/OS), and I'll have to experiment until it's right?
The resistors can be with the led on the frontplate, right?
TIA
david
I was thinking about bringing every LED from my amp (F4) to the front-panel.
That is, 2 from the universal PSU, 2 from the amp-channels, and (?) 2 from the speaker protection (if they light up at all) - so 2 or 3 different sources.
Brightness will be adjusted through resistors.
Will their respective brightness be the same (with the same resistors), or will they vary depending the source (PSU/OS), and I'll have to experiment until it's right?
The resistors can be with the led on the frontplate, right?
TIA
david
Do these appliances use the same type of LED? If not get the same type of LED.
Brightness varies with current. Measure the voltage between the nodes the current set resistor and the LED are connected to. Choose resistors that set the same current through the LEDs in the appliances.
Check if the LED in the amplifier has also a biasing function or is purely a status LED that shows if the unit receives power and check/reset bias after change to another type.
The resistors can be anywhere within the current loop, before or after the LED.
Brightness varies with current. Measure the voltage between the nodes the current set resistor and the LED are connected to. Choose resistors that set the same current through the LEDs in the appliances.
Check if the LED in the amplifier has also a biasing function or is purely a status LED that shows if the unit receives power and check/reset bias after change to another type.
The resistors can be anywhere within the current loop, before or after the LED.
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The LEDs may be used in the amplifier circuits wherever a voltage reference of about 1.2Vdc or so is needed. The LEDs are likely to glow at different brightness, depending upon the circuit they are in.
And different coloured LEDs may have different brightness (I think this can be determined from the forward voltage value of the LED, but I defer to more knowledgeable members to clarify this).
If each LED is the same (ie, colour), it gets the same voltage and has the same value resistor, they should have the same brightness.
I always err on having a slightly larger resistor than calculated, there is less chance of the LEDs failing (they will be slightly duller, but I find the brightness very adequate).
If each LED is the same (ie, colour), it gets the same voltage and has the same value resistor, they should have the same brightness.
I always err on having a slightly larger resistor than calculated, there is less chance of the LEDs failing (they will be slightly duller, but I find the brightness very adequate).
Hi David,
Just make sure the LED isn't used as a voltage reference. If it goes open, that circuit will conduct maximum current and destroy itself in the process. Those LEDs really ought to remain on the PCB. If you look, you will probably see them in the base circuit of a BJT. They are also run at a specific current, so don't change it as that will possibly change the current that circuit is set to.
If the LED is only an indicator, then the brightness depends on the current it is running at and the efficiency of that LED. Also, LEDs in colours your eyes are more sensitive to will appear brighter. Your best bet might be to line the different LEDs up and run them at the same current as a starting point. Then, adjust the current to make them appear to be the same brightness. Once that is done you can simply select resistances in the circuits to run the same currents you found in your test.
It is a little work, but worth it for you. Just be absolutely certain you do not move an LED used as a voltage reference in a current source to the front panel. Those must stay on the PCB!
-Chris
Just make sure the LED isn't used as a voltage reference. If it goes open, that circuit will conduct maximum current and destroy itself in the process. Those LEDs really ought to remain on the PCB. If you look, you will probably see them in the base circuit of a BJT. They are also run at a specific current, so don't change it as that will possibly change the current that circuit is set to.
If the LED is only an indicator, then the brightness depends on the current it is running at and the efficiency of that LED. Also, LEDs in colours your eyes are more sensitive to will appear brighter. Your best bet might be to line the different LEDs up and run them at the same current as a starting point. Then, adjust the current to make them appear to be the same brightness. Once that is done you can simply select resistances in the circuits to run the same currents you found in your test.
It is a little work, but worth it for you. Just be absolutely certain you do not move an LED used as a voltage reference in a current source to the front panel. Those must stay on the PCB!
-Chris
How would you be able to determine this?
(I don't have in-depth electronics knowledge).
F4 First Watt this one ??
https://www.firstwatt.com/pdf/prod_f4_man.pdf
According to the schematic the leds are indicators, no problem bringing them to front.
Brightness of LEDs depends on their detailed construction, most modern LEDS are multilayer heterojunction types (aka quantum well), and manufacturers strive to improve efficiency so they've been getting brighter over the years.
Basically if you need the same brightness, you need the exact same type at the same current, or you'll have to look at datasheets for the information and figure it out, including beam angle (the lens has an effect on perceived brightness too).
Basically if you need the same brightness, you need the exact same type at the same current, or you'll have to look at datasheets for the information and figure it out, including beam angle (the lens has an effect on perceived brightness too).
> if you need the same brightness, you need
An alternative to matching LEDs is to match some photo-diodes (or do some switching, electric or optic) to monitor and regulate brightness.
But when I wanted to monitor +12V and +35V using relative brightness as evidence it wasn't partly sick, it only took a minute with a fistful of resistors to make the two different supplies and low-quality LEDs "match" as far as the eye could tell.
An alternative to matching LEDs is to match some photo-diodes (or do some switching, electric or optic) to monitor and regulate brightness.
But when I wanted to monitor +12V and +35V using relative brightness as evidence it wasn't partly sick, it only took a minute with a fistful of resistors to make the two different supplies and low-quality LEDs "match" as far as the eye could tell.