LED Spectrum Analyzer

[audioguru]

I see your supply voltage is 9V. The circuit I use has a 12V supply. I am assuming that since the MC33172 can go to 44V that the op amp will be fine, but will that change any of the other component values in the circuit?

The LM3915 might melt if all the LEDs are lighted (bar mode) with 27mA each (bright setting). Then the total current in the LM3915 is 270mA. The 10 ohm resistor drops 2.7V and the LEDs drop 3.4V so with a 12.0V supply the LM3915 dissipates 1.6W. Its max allowed dissipation is 1.365W at room temperature and is less when it is enclosed.
Calculate a suitable current-limiting resistor (mine is 10 ohms) and a suitable max current for the LEDs. Of course your LEDs have a different forward voltage than mine.

You use an electret microphone for your source. I will be using the output of the line level jacks of a car stereo. What design problems do you forsee using this higher input source?

The first opamp can have its gain reduced then the electret mic and R1 can be replaced with a 10k volume control.

 

[d3dreaper]

Alright now i realize i have another problem....
What is the power voltage in the velleman k4300?? I see it has Va Vb and Gnd and on Va and Vb it has 1000v diodes on it. would that tell me its going to be 120V AC power input??

 

[audioguru]

The Velleman k4300 is not on their website anymore so we cannot see the schematic.
They use 1000V diodes becuse they are inexpensive and then they stock only one diode instead of a few.

 

[saturn1bguy]

would that tell me its going to be 120V AC power input??

No.

It requires 12-15VDC, or a transformer with a secondary in the range of 18-25.2VCT...

 

[d3dreaper]

So for that beginning voltage is just 12-18 volt roughly? Confusin people labeling the first section a power supply...

 

[don.3007]

ronsimpson Thnx Man

 

[saturn1bguy]

So for that beginning voltage is just 12-18 volt roughly? Confusin people labeling the first section a power supply...

I have no idea what you just said...

Either:
1) Apply a DC voltage of 12V to 15V at VA or VB, referenced to GND, or

2) Slap on a transformer with a center-tapped secondary of 18VAC to 25.2VAC, outside legs to VA and VB, with the center tap tied to GND.

 

[Mikebits]

I have no idea what you just said...

You can't handle what he just said... This forum is out of order.

Oops, wrong movie scene...

 

[MrDEB]

Same project I was/am working on

Have a completed schematic.
Looked at doing the multi plexing thing -way to involved.
attached if I can locate pics of schematic.
As for software for testing designs I found TINA very good and easy to use.
Its FREE for the limited version.
Will get back to you when I locate the right schematic

 

[MrDEB]

Found schematic BUT!!

it is in 7 pages in a schematic/pcb program called expresspcb
very good program and its free as well.
would be happy to send file if you want.Includes an almost complete pcboard as well.
I also did a pocket VU meter as well.
I used 10 - LM 3916 I found real cheap??

 

[audioguru]

I have a completed schematic.
Looked at doing the multiplexing thing -way too involved.

I remember that you worked on your Audio Spectrum Analyser months ago using multiplexing.
Does it work alright without multiplexing?
Is it nice and bright?

 

[MrDEB]

no multi plexing for me

I recall we conversed about multi plexing and found it to complicated as far as number of parts and the low current feeding the leds.
Went with ten LM3916's.
came out cheaper than multi plexing.
as far as completig the project -- hav'nt completed it as the boy scout I am working with on project has been busy with school etc. as well as me being busy helping my brother remodel his house.
this past summer I consider LOST
planning on resuming the electronic project as well as my building a "mood light" for my wife's entertainment unit I finally built after 5 years.
see cabinet lighting post.
I am wondering about the connection of pin 2 to pin 1 of a 4029.

 

[d3dreaper]

alright the power supply and input section of the k4300
**broken link removed** i was tryin to figure out what the starting voltage is on Va and Vb

 

[audioguru]

The power supply for the K4300 kit is 12VDC to 15VDC. A or B is positive.
The lousy old LM324 quad opamp is much too noisy and is much too slow.
The input opamp is connected as a low input impedance inverting type for an old dynamic microphone. It should be connected as a non-inverting type that has a high input impedance for a modern electret mic.

EDIT: The power supply inputs a and B are from a 9V-0V-9V center-tapped to ground mains transformer.

 

[d3dreaper]

So that would've been genuis for a fireworks show in your living room to connect it to 120vac haha thanks a lot I've been tryin to figure that out and even my teacher had agreed with th 120vac connection there. Guess I gotta tell him about it too

 

[audioguru]

Tell your teacher that he (she or it) is a dumbo.

 

[Mikebits]

Tell your teacher that he (she or it) is a dumbo.

Perhaps you may want to wait until grades are posted before doing such a thing.

 

[audioguru]

Please give me the e-mail address of the dumbo teacher and I will tell him, her or it.

 

[lasvegasmale31]

Have a completed schematic.

Care to Email a copy of your schematics??

 

[d3dreaper]

I don't think he'd be to happy about that lol. He is about the same in knowledge in electronics as me but I'm a little more ambitious on taking on bigger and bigger projects. He said the biggest project he has worked on was a phototheremin that we made in class using a 555timer