Wiener group buy #2 - Stereo and PBTL editions available!

[jean-paul]

With 2 mA normal 3 mm green/amber/red LEDs glow dimmed which is nice. Many of us don't want a flashlight lighting up the whole room.

Normal LEDs have a Uforward of around 1.6V. Blue and white LEDs often have 2.5 to 4V.

 

[Hypertext]

The LED's voltage needs to be less than or equal to your power supply voltage. This is called the "turn on" voltage of the LED. If the LED's turn on voltage is greater than your power supply voltage, then the LED won't turn on. But, a reasonable assumption is that your power supply will be greater than 12V (I think the TPA3118 supports voltage down to 5V or so, but I don't recall seeing anyone going below 12V). The most common voltages I've seen people use for these amps are 12, 13.8, 18-21, and 24.

Of course LEDs are available in just about any voltage you can imagine, but at least when I've shopped Mouser/DigiKey, most LEDs tend to be in the 2V range.

The other thing to look at with the LEDs are the max current. If you run more current through them than that, you'll likely blow them (or at least dramatically lower their life).

I too am mostly just a guy who likes to bust out the soldering iron on the weekends, but specifying an LED is something I feel comfortable doing! Here's the "cheat sheet" formula:

(power supply voltage - LED voltage) / resistor value = LED current

Note: voltages are expressed in Volts, resistor values are specified in Ohms (or kOhms which is equal to 1000 Ohms), and current is specified in Amps (or likely milliamps = 0.001 Amps).

You should know the voltage of the power supply you'll be using (like I said, I'm guessing somewhere between 12 and 24 volts).

The LED voltage you can easily see on the LED's datasheet, usually it's a search parameter on places like Mouser or DigiKey.

The resistor is on the board, that's 2.2 kohms (which is the same as 2200 ohms).

Plug in the numbers and you'll get the LED current. Make sure that is below the LED's rated current (which will also be quite plain in the datasheet and/or seller's listing).

In my limited experience, I've found that most LEDs are obscenely bright, and in practice you'll probably want the LED current to be significantly less than the LED's rated current. If you find the LED is too bright, you can always add more resistance to lower the current. Lowered current will not only dim the LED, but lengthen it's life as well.

OK that helps. You are still way ahead of me in the understanding. I don't get this, "The other thing to look at with the LEDs are the max current. If you run more current through them than that, you'll likely blow them (or at least dramatically lower their life)"

EDIT. OK, I found an explanation of why a resistor is needed for a LED, it draws amps until it dies.

damn, all this just for the power LED, and I still have to find out what the other parts do

 

[jean-paul]

It's a start. Many things to discover !

 

[cogitech]

damn, all this just for the power LED, and I still have to find out what the other parts do

Part of it is knowing what matters and what doesn't.

When I chose the LED for this board, I literally poked my finger around in a bunch of random components in my bin and grabbed the first LED that I found. No thoughts of voltage or amperage, or anything of the sort. Just "ummm, I need an LED... hmmmm... oh, there's one."

 

[Hypertext]

Part of it is knowing what matters and what doesn't.

When I chose the LED for this board, I literally poked my finger around in a bunch of random components in my bin and grabbed the first LED that I found. No thoughts of voltage or amperage, or anything of the sort. Just "ummm, I need an LED... hmmmm... oh, there's one."

well, I have no parts bins, and I did not want to burn up a circuit with the wrong LED.
the easy way to answer my initial question would be to ask what power supply I'm using, in my case 19.5V, then suggest a LED

 

[cogitech]

well, I have no parts bins, and I did not want to burn up a circuit with the wrong LED.
the easy way to answer my initial question would be to ask what power supply I'm using, in my case 19.5V, then suggest a LED

Certainly good to be cautious.

I guess I am having trouble imagining a scenario with an LED that would end in tragedy (other than a dead LED).

Anyway, you got your question answered (and the some!) so it's "all good".

 

[matt_garman]

well, I have no parts bins, and I did not want to burn up a circuit with the wrong LED.
the easy way to answer my initial question would be to ask what power supply I'm using, in my case 19.5V, then suggest a LED

In this particular situation, I believe the worst-case scenario is you either burn up the LED, or the LED doesn't turn on. So the risk to the Wiener board is virtually nil.

Here's the LED I've been using in my recent builds: DigiKey 67-1151-ND, Lumex Opto/Components Inc part number SSI-LXR3612ID.

You can see on the product listing the forward voltage is 2V, and the max current is 30 mA (=0.03 Amps).

So, plugging into the formula I posted above:

(19.5V - 2V) / 2200ohm = 0.008 Amps = 8mA. That's well below the max of 30mA. So the LED will be perfectly safe. IIRC, I used around a 2kohm resistor with a 20V power supply, so very similar numbers. The brightness is "just right" (for me), and the LED is plenty safe.

Just to further the example: say you wanted to run that LED at maximum brightness, then you'd want a resistor around 583 ohms. (Note resistors usually have a tolerance, so you'd want to go a little bigger for safety of the LED. But from personal experience, I can assure you, this particular LED is way too bright at max current.)

Hope that helps!

 

[Hypertext]

Certainly good to be cautious.

I guess I am having trouble imagining a scenario with an LED that would end in tragedy (other than a dead LED).

Anyway, you got your question answered (and the some!) so it's "all good".

right, to most DIY guys in here, they know in a worse case scenario the LED goes boom and that's it, whereas I don't know these things, and I wanted to ask when plugging in components on a over $100 amp

 

[Hypertext]

The LED's voltage needs to be less than or equal to your power supply voltage. This is called the "turn on" voltage of the LED. If the LED's turn on voltage is greater than your power supply voltage, then the LED won't turn on. But, a reasonable assumption is that your power supply will be greater than 12V (I think the TPA3118 supports voltage down to 5V or so, but I don't recall seeing anyone going below 12V). The most common voltages I've seen people use for these amps are 12, 13.8, 18-21, and 24.

Of course LEDs are available in just about any voltage you can imagine, but at least when I've shopped Mouser/DigiKey, most LEDs tend to be in the 2V range.

The other thing to look at with the LEDs are the max current. If you run more current through them than that, you'll likely blow them (or at least dramatically lower their life).

I too am mostly just a guy who likes to bust out the soldering iron on the weekends, but specifying an LED is something I feel comfortable doing! Here's the "cheat sheet" formula:

(power supply voltage - LED voltage) / resistor value = LED current

Note: voltages are expressed in Volts, resistor values are specified in Ohms (or kOhms which is equal to 1000 Ohms), and current is specified in Amps (or likely milliamps = 0.001 Amps).

You should know the voltage of the power supply you'll be using (like I said, I'm guessing somewhere between 12 and 24 volts).

The LED voltage you can easily see on the LED's datasheet, usually it's a search parameter on places like Mouser or DigiKey.

The resistor is on the board, that's 2.2 kohms (which is the same as 2200 ohms).

Plug in the numbers and you'll get the LED current. Make sure that is below the LED's rated current (which will also be quite plain in the datasheet and/or seller's listing).

In my limited experience, I've found that most LEDs are obscenely bright, and in practice you'll probably want the LED current to be significantly less than the LED's rated current. If you find the LED is too bright, you can always add more resistance to lower the current. Lowered current will not only dim the LED, but lengthen it's life as well.

so what happens if my neighbor runs his 12 volt LED under cabinet light strips that he just got ( that he was told to use a 12 volt DC 6A power supply) with a 24 volt DC power supply ? I bet it draws more current at 24V, and possibly overloads the rated current of the LED

 

[doctormord]

The Wiener is no slouch. In most average living rooms it will be more than sufficient, even at quite loud SPL. I can easily push my system to SPL in the mid 90dBc range (peaks) and it seems to do so quite effortlessly.

OT:

Well, even the stereo board performs very well at high levels, running a 3132D2 in my bike setup at 122db (129dB peak).

So PBTL is sufficient for alot "ompf" when driving low impedance speakers.

 

[matt_garman]

so what happens if my neighbor runs his 12 volt LED under cabinet light strips that he just got ( that he was told to use a 12 volt DC 6A power supply) with a 24 volt DC power supply ? I bet it draws more current at 24V, and possibly overloads the rated current of the LED

He voids his warranty

I suppose if his cabinet lights are just a bunch of LEDs direct-connected to the power supply, then yes, the current across the diodes would increase. The lights will get brighter and/or not last as long and/or blow out immediately. Could possibly be a fire hazard in the worst case.

But there's probably some kind of circuit that sits between the lights and the PSU, so it's impossible to say.

It's a completely different question than asking about what LED to use with your amp. I would consider the cabinet lighting an off the shelf consumer electronics product. The right answer there is almost always to do what the manufacturer recommends. Doing otherwise implies you have more than a superficial understanding of the circuit.

 

[Hypertext]

OK thanks everyone. My next question will be on installing electric heaters on my milking machine pulsators, since the cows complain in the wintertime about the cold metal.

I better take this question to Farm Chat

 

[jean-paul]

Part of it is knowing what matters and what doesn't.

When I chose the LED for this board, I literally poked my finger around in a bunch of random components in my bin and grabbed the first LED that I found. No thoughts of voltage or amperage, or anything of the sort. Just "ummm, I need an LED... hmmmm... oh, there's one."

If I would do that there would be a chance that a high efficiency type (bright!), high power or low current type could be found. 3 or 5 mm, square, round, triangular, green, traffic light green, red, amber, pink, blue, white, IR.........

So essentially even a LED sometimes needs some thought

 

[bruce potter]

bk856er: Two bare PBTL PCBs + 2 uC's
snake69fast: Two bare PBTL PCBs + 1 stereo PCB + 3 uC's
lostthumb: Two bare PBTL PCBs + 1 stereo PCB + 3 uC's
eplates: 1x fully assembled stereo card with filter kit
Ginum: 1 bare PBTL PCB + 1 stereo PCB + 2 uC's
rhing: Two bare PBTL PCBs + IC's installed and uC's installed
bchristmas: Two bare PBTL PCBs + IC's installed and uC's installed
iamdarren73: Two bare PBTL PCBs + IC's installed and uC's installed and impedance matching kits for the pair
brucepotter: 1 fully assembled stereo card with filter kit

 

[bk856er]

I count 18 boards so far.

Nearly there!

BK

 

[gmarsh]

Definitely enough interest for me to order the PCB's.

But so far only 6 fully assembled stereo cards (two here, and someone from the previous group buy who wants 4 cards built out). I'll recalculate the parts cost for qty 10 versus 25 and if everyone's cool with fully built cards and filter kits costing $5 or so more, I'll go ahead with the buy.

 

[bk856er]

I'm totally fine with built cards and filter kits going up a measly ~$5.

BK

 

[Alfi]

Hi,
I'm interested in 1 fully assembled stereo card with filter kit.

 

[gmarsh]

OK, I'm going to kick off the group buy order this evening.

I've got 3 remaining sets of 10uH inductors, which will cover the orders so far, and it saves me from having to do another Jotrin order for Sagami inductors. I can take more stereo card orders, but they'll have to be 8 ohm, or 6 ohm using a 15uH inductor. I wish ICE would get their act together and get some 10uH inductors stocked somewhere...

I'll tack $5 onto the pricing for fully built cards, due to the crappy canadian dollar and parts being ordered qty 10 versus qty 25. Bare PCBs are still $8.

 

[lostthumb]

bk856er: Two bare PBTL PCBs + 2 uC's
snake69fast: Two bare PBTL PCBs + 1 stereo PCB + 3 uC's
lostthumb: Two bare PBTL PCBs + 1 stereo PCB + 3 uC's + IC's installed
eplates: 1x fully assembled stereo card with filter kit
Ginum: 1 bare PBTL PCB + 1 stereo PCB + 2 uC's
rhing: Two bare PBTL PCBs + IC's installed and uC's installed
bchristmas: Two bare PBTL PCBs + IC's installed and uC's installed
iamdarren73: Two bare PBTL PCBs + IC's installed and uC's installed and impedance matching kits for the pair
brucepotter: 1 fully assembled stereo card with filter kit[/QUOTE]

Modified order in red.