Wiring leds on Rotary selector

[century tek]

Probably something like OCD.

 

[I LIKE MUSIC]

This is a tough crowd, I used the correct letters, now I am expected to have them in the correct order...

Picky, picky picky.

 

[vha]

You will have to experiment. I don't know anything about the efficiency of the particular LEDs you are using, or what brightness you would consider acceptable.

4k7 will give you about 5mA. Even that might be too bright.

You can, of course, calculate the power that will be dissipated in the series resistor: P=V^2/R

So, for a 24V supply, 3V forward voltage and a 4k7 resistor, you'll be dissipating less than 100mW. A 0.5W (or higher) rated resistor will be fine.

So the higher is the resistor the less brightness will get

 

[cpt_paranoia]

Yes. Brightness is determined by current (for a given diode). From Ohm's law, V=IR, we re-arrange to get I=V/R. I being the current...

That's in the series resistor. The diode isn't a resistor, so Ohm's law doesn't work with the forward voltage and current. Semiconductor physics determines the voltage and current for a diode...

 

[vha]

I know this. We said to test several resistors for the brightness of the led

As I suggested above, I would experiment with resistor values. 25mA with a modern blue or white LED is likely to be far too bright for comfort.

I know ..
We said above to test several resistors for the brightness of the led therefore as we test higher resistor the brightness is getting less..

 

[willyrover]

Just throwing this out as another option.

These input boards are available on eBay and aren't expensive. Allows you to keep signal path short and takes care of the input LEDs. (They come mounted to the board but could easily be removed and brought out to the front panel.)



I used one in my DIY preamp and have been very happy with it.

 

[cpt_paranoia]

I know this.

You know what? If you knew that a higher resistance meant lower brightness, why did you ask this question (which is what I was answering)?

So the higher is the resistor the less brightness will get

 

[vha]

Ah ok ...
we need to understand each other I said I know that The diode isn't a resistor,...
My question was on the values of the resistors etc... also because I had to calculate also for the second amp which is supplied by 12V and I went to purchase the resistors..
Thank you

 

[vha]

Just throwing this out as another option.

These input boards are available on eBay and aren't expensive. Allows you to keep signal path short and takes care of the input LEDs. (They come mounted to the board but could easily be removed and brought out to the front panel.)

View attachment 1315775

I used one in my DIY preamp and have been very happy with it.

View attachment 1315776

Yes Thank you
I will probably use these type for next amp