power LED

[aragorn723]

how hard would it be to add an LED on the quickie next to the power switch so you can see when it is on?  Also, would it affect the sound?

[Paul Joppa]

Put it in the plate circuit (as I've said before) - actually, between any of the 9-v batteries. It will drop the battery voltage a bit, but should not really affect their life significantly.

[aragorn723]

Put it in the plate circuit (as I've said before) - actually, between any of the 9-v batteries. It will drop the battery voltage a bit, but should not really affect their life significantly.

Sorry for the repeat question, couldn't find anything in the search on the forum for this topic.  I searched an electronic supplier, and found a bunch of different blue ones, but wasn't sure of what voltage rating to pick?  There weren't any with a 36 volt rating, and a few of the choices mentioned voltage-dropping resistors that come with it, so i'm assuming there need to be some resistors hooked up to the LED so that its voltage spec isn't exceeded?  How does this work? 

[galyons]

There are calculators for current limiting resistor values.  Here is an easy one to use:
http://led.linear1.org/led.wiz.  Look for an LED that has minimal current requirements, (low mA).

Cheers,
Geary

[aragorn723]

There are calculators for current limiting resistor values.  Here is an easy one to use:
http://led.linear1.org/led.wiz.  Look for an LED that has minimal current requirements, (low mA).

Cheers,
Geary

Thanks.. If I enter 3.4v as the forward voltage, and 20ma as the forward current, then 36 v (quickie plate voltage).  That generated a power dissipation concern in the calculator..  Looks like they use a 60% rule for the dissipation, so based on that, they recommend a value of around 1.3 watts (total dissipation of 788MW / 1000 = .788 Watts / .6=1.3Watts.  How about putting the LED after 1 9 volt battery?  It probably wouldn't be as bright, but it looks like a 1/4 watt resistor would do it (so there is only one resistor after the LED?? no diode?  Any thoughts?  Thanks,

Dave

[Paul Joppa]

Use a red one - they have the lowest voltage drop - and put it in series with the 36v supply.

[aragorn723]

Use a red one - they have the lowest voltage drop - and put it in series with the 36v supply.

What voltage would I use to calculate the current limiting resistor value based on hooking up the LED like that?

[Paul Birkeland]

No current limiting resistor is necessary, the tubes themselves will determine the current.

[adamct]

Which of the below is a better choice? I assume Option #2?

Option 1: http://www.mouser.com/ProductDetail/Everlight/MV7044/?qs=sGAEpiMZZMtmwHDZQCdlqfcjWz0UiOrXSSCAAaamEYM%3d

I note that the absolute maximum ratings are as follows (according to the data sheet):

DC forward current: 30 mA
Peak forward current: 160 mA
Power dissipation: 85 mW
Reversed voltage: 5V
Forward voltage: 2.1V typical, 2.8V maximum
Typical luminosity: 375 mcd

Option 2: http://www.mouser.com/ProductDetail/Kingbright/WP7113SRD14V/?qs=sGAEpiMZZMtmwHDZQCdlqS%252b42B3%252blPHXEzLnpxnIXBI%3d

Absolute maximum ratings according to data sheet:

Forward current:  13.5 mA
Power dissipation:  160 mW
Reversed voltage: 5V
Forward voltage: 16V maximum
Typical luminosity: 100/300 mcd (unclear which value is correct)

Would option #2 also be suitable for use in a S.E.X., as described here? http://www.bottlehead.com/smf/index.php/topic,3877.0.html

[Doc B.]

I would also consider how bright you want that power indicator to be. I like a really soft light, and I tend to choose LEDs with a very low light output. Some of those high output blue ones give me a headache from across the room.

[adamct]

Agree. But I can't figure out which values I need to pay attention to in terms of selecting an LED for this application (or in the S.E.X.)...

I know a lot of people use the LED in Option 1 for various things, but I note that it has 2.8V maximum "forward" voltage. Is that too low for use here? Or for use in the S.E.X.?

[Paul Birkeland]

Agree. But I can't figure out which values I need to pay attention to in terms of selecting an LED for this application (or in the S.E.X.)...

I know a lot of people use the LED in Option 1 for various things, but I note that it has 2.8V maximum "forward" voltage. Is that too low for use here? Or for use in the S.E.X.?

The SEX and the Quickie have very different considerations.

In the Quickie, the current drawn by the circuit is to be drawn through the LED, with the forward voltage drop being lost from the B+ in the process.  Under these conditions, your first LED looks much better, though I'd be looking for something 2V or less with maybe 5% of the brightness of that particular LED.

In the SEX amp, you can use a dropping resistor and the 6.3V DC supply that heats the tubes.  Take your LED's forward voltage, then subtract that from 6.3.  Next, divide this remaining voltage by the current you want to run through your LED (in Amps) to find your dropping resistor.  Generally, 10mA is a good starting point for most LED's. 

-PB

[adamct]

Awesome. Thanks, Paul!

[pushbroom]

hope this doesn't constitute hijacking the thread, but would it be possible to incorporate this product as an on/off indicator?

http://www.oznium.com/led-ribbon
http://www.oznium.com/led-ribbon/tech (for data sheet)

i would assume they would need their own dedicated power source, would the switch have to be replaced to incorporate the additional power supply? or could the existing circuitry support such an addition (with minor modification) without negatively affecting the sound quality?  i apologize if my noob is showing...i intend on stringing the inside of my backbox with these so the entire unit illuminates through the acrylic chassis when turned on

[Paul Birkeland]

i would assume they would need their own dedicated power source, would the switch have to be replaced to incorporate the additional power supply?

Yes, you will need to go with a 5P3T rotary switch, which is very uncommon.  A Goldpoint 4P-3T-2D will get the job done, but it's a $107 switch.

This might work too, but I have no experience with that particular switch.

-PB