Converting VU meter design to single power supply

[Tom Corker]

I'm looking inot building a VU meter based on the design at
http://www.4qdtec.com/avu.html. This design specifies a +18v-0v-18v
split power supply. However, I need to run it from a 12v single power
rail.
Can I just tie the bottom of the LED set to ground, instead if -18v
via the 2 transistors?
Also, would BC109 transistors be suitable?

I am something of a beginner in electronics.
Thanks.

 

[Martin Griffith]

I'm looking inot building a VU meter based on the design at
http://www.4qdtec.com/avu.html. This design specifies a +18v-0v-18v
split power supply. However, I need to run it from a 12v single power
rail.
Can I just tie the bottom of the LED set to ground, instead if -18v
via the 2 transistors?
Also, would BC109 transistors be suitable?

I am something of a beginner in electronics.
Thanks.

All the leds are in series, and yoy will drop over a volt on each one,
so that is the minimum rail that you can get away with, plus a bit
more for safety.
Look at the LM3914/3915/3916 from national, far more friendly, and
will work from 12V and will be more stable


martin

 

[ehsjr]

I'm looking inot building a VU meter based on the design at
http://www.4qdtec.com/avu.html. This design specifies a +18v-0v-18v
split power supply. However, I need to run it from a 12v single power
rail.
Can I just tie the bottom of the LED set to ground, instead if -18v
via the 2 transistors?
Also, would BC109 transistors be suitable?

I am something of a beginner in electronics.
Thanks.

You need a different circuit to use a single 12 volt supply
and light up 10 LEDs.

Ed

 

[Eeyore]

I'm looking inot building a VU meter based on the design at
http://www.4qdtec.com/avu.html. This design specifies a +18v-0v-18v
split power supply. However, I need to run it from a 12v single power
rail.

You can't, there won't be enough volts to illuminate all the series
leds..

Graham

 

[Eeyore]

All the leds are in series, and yoy will drop over a volt on each one

Rather more than a volt. At a few mA I use 1.6V as Vf.

Graham

 

[[email protected]]

I'm looking inot building a VU meter based on the design athttp://www.4qdtec.com/avu.html. This design specifies a  +18v-0v-18v
split power supply. However, I need to run it from a 12v single power
rail.
Can I just tie the bottom of the LED set to ground, instead if -18v
via the 2 transistors?
Also, would BC109 transistors be suitable?

I am something of a beginner in electronics.
Thanks.

Yoicks, try something that's from this decade. That design is
ridiculous overkill and needlessly complex.

 

[Jim Thompson]

Yoicks, try something that's from this decade. That design is
ridiculous overkill and needlessly complex.

Surf on "bargraph"... IIRC National makes a chip ideally suited for
this purpose.

...Jim Thompson

 

[Martin Griffith]

Rather more than a volt. At a few mA I use 1.6V as Vf.

Graham

1+1=3 for greater values of 1


martin

 

[Tom Corker]

Yoicks, try something that's from this decade. That design is
ridiculous overkill and needlessly complex.

That was the main reason I wanted to build it. I know the purpose
specific ICs will do a better job, be cheaper, less complex etc, but I
really wanted to have a go at building something more than just an IC
and a bunch of LEDs. I'm building it more for the fun of it than any
actual practical use.
I've found a more suitable design at
http://www.talkingelectronics.com/projects/StereoVUmeter/StereoVU.html
Thanks for everyone's advice.

 

[[email protected]]

On 5 Feb, 19:52, [email protected] wrote:> Yoicks, try something that's from this decade. That design is

That was the main reason I wanted to build it. I know the purpose
specific ICs will do a better job, be cheaper, less complex etc, but I
really wanted to have a go at building something more than just an IC

I actually understand that, being a tube geek at times.

and a bunch of LEDs. I'm building it more for the fun of it than any
actual practical use.

And the first thing you wanted to do was find out which parts you
could change or throw away!?????

I've found a more suitable design athttp://www.talkingelectronics.com/projects/StereoVUmeter/StereoVU.html
Thanks for everyone's advice.

The LM3914 has been in production for *decades* and is still
available.
http://www.national.com/mpf/LM/LM3914.html
"Full production"

http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2556426;keywords=lm3914

 

[Spajky]

I'm looking inot building a VU meter ..., I need to run it from a 12v single power
rail.

I am something of a beginner in electronics.

check my site (down) under electronics for another schematic (LED
logaritmic Peak audio meter 4 PC) ...

 

[neon]

that will become an indicator not a VU meter ever