Hi everyone,

I want to build a gadget to flash 3 different groups of ten LEDs - to
be controlled by a microcontroller. I want these flashes to be
determined by the level of an audio signal (peak 5v.) So, in short, I
am looking for an easy-to-program microcontroller device with a built
on A/D converter that will accept a max 5v AC signal.

Any suggestions?
Thanks.

"Johnno" <cppj...@hotmail.com> wrote in message

news:1172036800.193498.138070@p10g2000cwp.googlegroups.com...

Hi everyone,

I want to build a gadget to flash 3 different groups of ten LEDs - to
be controlled by a microcontroller. I want these flashes to be
determined by the level of an audio signal (peak 5v.) So, in short, I
am looking for an easy-to-program microcontroller device with a built
on A/D converter that will accept a max 5v AC signal.

Any suggestions?
Thanks.

PIC and AVR both have A/D converters, and there are free programming tools
for both. My preference is for AVR because there is a free C compiler -- I
hate working in BASIC !!

Even the smallest versions of these processors have more than adequate I/O,
and most have internal oscilators so you dont have to mess with crystals.
Speed is limited without the xtal -- usually 1mhz -- but these are RISC
chips, so 1 million instructions per second -- which is more than adequate
for A/D stuff and and integer version of the FFT to detect the bass beats..
if it turns out you need a little more UMPH !! -- add the crystal and take
it up to 8mhz or better depending on the specific chip. All have on board
timers which makes clocking the A/D sample rate easy, and while most all
have PWM outputs, there are some with THREE pwm outputs, which would be
interesting if you wanted to modulate the intensity of the LEDs rather than
just flashing them.

Pretty much all these features and variations are available either the PIC
or AVR, so its really more a question of what languages you are comfortable
with, and what development tools are available, as both chips are about
equally easy to program for.

No matter which you choose, I strongly suggest getting the hardware
developers kit for the one you choose -- saves you the trouble of having to
debug both hardware and software at the same time.

On Feb 21, 2:52 pm, "John Barrett" <ke5c...@verizon.net> wrote:
"Johnno" <cppj...@hotmail.com> wrote in message

news:1172036800.193498.138070@p10g2000cwp.googlegroups.com...

Hi everyone,

I want to build a gadget to flash 3 different groups of ten LEDs - to
be controlled by a microcontroller. I want these flashes to be
determined by the level of an audio signal (peak 5v.) So, in short, I
am looking for an easy-to-program microcontroller device with a built
on A/D converter that will accept a max 5v AC signal.

Any suggestions?
Thanks.

PIC and AVR both have A/D converters, and there are free programming
tools
for both. My preference is for AVR because there is a free C compiler --
I
hate working in BASIC !!

Even the smallest versions of these processors have more than adequate
I/O,
and most have internal oscilators so you dont have to mess with crystals.
Speed is limited without the xtal -- usually 1mhz -- but these are RISC
chips, so 1 million instructions per second -- which is more than
adequate
for A/D stuff and and integer version of the FFT to detect the bass
beats..
if it turns out you need a little more UMPH !! -- add the crystal and
take
it up to 8mhz or better depending on the specific chip. All have on board
timers which makes clocking the A/D sample rate easy, and while most all
have PWM outputs, there are some with THREE pwm outputs, which would be
interesting if you wanted to modulate the intensity of the LEDs rather
than
just flashing them.

Pretty much all these features and variations are available either the
PIC
or AVR, so its really more a question of what languages you are
comfortable
with, and what development tools are available, as both chips are about
equally easy to program for.

No matter which you choose, I strongly suggest getting the hardware
developers kit for the one you choose -- saves you the trouble of having
to
debug both hardware and software at the same time.

Great! I am familiar with C so I'll check out the AVRs.

Seeing as I am planning on having three banks of colours, with 10 LEDs
for each colour, that makes up a total of 30 LEDs which I need the
controller to be able to switch on or off. Any ideas on what hardware
would be suitable for an application like this?

Perhaps something like the following: Microcontroller >----
(serial output, perhaps)------>Serial to bit decoder-->LED Drivers

Thanks very much for your involvement,
John.

Thanks again, although I need to be able to independently control 30
different LEDs. Either I didn't explain this clearly .. or.. do AVRs
really support 30 seperate outputs? (By bank I simply mean a group of
partiular coloured LEDs, I did not mean for this to cause confusion :P

Cheers
John

Thanks again, although I need to be able to independently control 30
different LEDs. Either I didn't explain this clearly .. or.. do AVRs
really support 30 seperate outputs? (By bank I simply mean a group of
partiular coloured LEDs, I did not mean for this to cause confusion :P

Cheers
John

Thanks again, although I need to be able to independently control 30
different LEDs. Either I didn't explain this clearly .. or.. do AVRs
really support 30 seperate outputs? (By bank I simply mean a group of
partiular coloured LEDs, I did not mean for this to cause confusion

On Feb 21, 1:13 am, "Johnno" <cppj...@hotmail.com> wrote:
Thanks again, although I need to be able to independently control 30
different LEDs. Either I didn't explain this clearly .. or.. do AVRs
really support 30 seperate outputs? (By bank I simply mean a group of
partiular coloured LEDs, I did not mean for this to cause confusion :P

Cheers
John

Total driving power would be a problem. You can probably drive a few
high power LED directly from each AVR. You can do as we do:

Running an ARM master micro, which can crunch FFT like peanuts
(perhaps 20 to 30 per second). Using Jtag to control slave AVRs.

In this setup: http://linnix.com/boards.jpg

4 I/O pins from the ARM (lower left) jtag control 20 pins of the AVR
(upper right, showing back side only). The plan is to have
additional chains and additional AVR per chain. Namely

ARM -> AVR -> AVR -> AVR
\> AVR -> AVR -> AVR

By the way, the AVRs are unprogrammed, just jtag enabled.
The ARM is programmed with USB Jtag.

Johnno wrote:
Thanks again, although I need to be able to independently control 30
different LEDs. Either I didn't explain this clearly .. or.. do AVRs
really support 30 seperate outputs? (By bank I simply mean a group of
partiular coloured LEDs, I did not mean for this to cause confusion :P

Even the smallest micro should be able to handle this by using external
shift registers (like the 74hc595 for example). You clock the bits out
serially (only takes a few pins (1 for clock, 1 for data, 1 for latching).
By chaining the shift-registers together, you could drive scores of LEDs
like this and update them many, many times per second (like thousands .
If you use a micro that has built in SPI, you can really go fast.

This should be helpful:
http://www.windmeadow.com/node/20

"Anthony Fremont" <spam-not@nowhere.com> wrote in message
news:12tomqdpm5a5jdf@news.supernews.com...
Johnno wrote:
Thanks again, although I need to be able to independently control 30
different LEDs. Either I didn't explain this clearly .. or.. do AVRs
really support 30 seperate outputs? (By bank I simply mean a group
of partiular coloured LEDs, I did not mean for this to cause
confusion :P

Even the smallest micro should be able to handle this by using
external shift registers (like the 74hc595 for example). You clock
the bits out serially (only takes a few pins (1 for clock, 1 for
data, 1 for latching). By chaining the shift-registers together, you
could drive scores of LEDs like this and update them many, many
times per second (like thousands . If you use a micro that has
built in SPI, you can really go fast. This should be helpful:
http://www.windmeadow.com/node/20


But the problem isnt controlling lots of LEDs -- he only has 3 banks
(10 leds each) .. so he only needs one output per bank -- besides ---
using a 3 to 8 decoder and 8 bit latches will get you 64 bits of
output using only 12 bits of microcontroller I/O.. or you could use
I2C i/o chips (256 per I2C bus, 8 bits per chip) and get 2048 bits of
control.. either solution is much simpler to deal with than shift
registers, and the shift register setup would have the pattern
shifting across the banks as you moved the bits along to their proper
position .. or were you going to add a blanking circuit to keep the
LEDs turned off while you shifted the data ??

The problem is detecting the beats so the lights sync to the
music..... Once you got that under control, controlling LEDs is a
no-brainer (even with neet little tricks like PWM brightness
control and such that would make this really cool)

John Barrett wrote:
"Anthony Fremont" <spam-not@nowhere.com> wrote in message
news:12tomqdpm5a5jdf@news.supernews.com...
Johnno wrote:
Thanks again, although I need to be able to independently control 30
different LEDs. Either I didn't explain this clearly .. or.. do AVRs
really support 30 seperate outputs? (By bank I simply mean a group
of partiular coloured LEDs, I did not mean for this to cause
confusion :P

Even the smallest micro should be able to handle this by using
external shift registers (like the 74hc595 for example). You clock
the bits out serially (only takes a few pins (1 for clock, 1 for
data, 1 for latching). By chaining the shift-registers together, you
could drive scores of LEDs like this and update them many, many
times per second (like thousands . If you use a micro that has
built in SPI, you can really go fast. This should be helpful:
http://www.windmeadow.com/node/20


But the problem isnt controlling lots of LEDs -- he only has 3 banks
(10 leds each) .. so he only needs one output per bank -- besides ---
using a 3 to 8 decoder and 8 bit latches will get you 64 bits of
output using only 12 bits of microcontroller I/O.. or you could use
I2C i/o chips (256 per I2C bus, 8 bits per chip) and get 2048 bits of
control.. either solution is much simpler to deal with than shift
registers, and the shift register setup would have the pattern
shifting across the banks as you moved the bits along to their proper
position .. or were you going to add a blanking circuit to keep the
LEDs turned off while you shifted the data ??

I must be dense, but I could swear that the OP keeps telling you that he
needs 30 separate outputs.

"Thanks again, although I need to be able to independently control 30
different LEDs. Either I didn't explain this clearly .. or.. do AVRs
really support 30 seperate outputs? (By bank I simply mean a group of
partiular coloured LEDs, I did not mean for this to cause confusion "

The problem is detecting the beats so the lights sync to the
music..... Once you got that under control, controlling LEDs is a
no-brainer (even with neet little tricks like PWM brightness
control and such that would make this really cool)

:-? He hasn't really mentioned that part yet. I don't mean to be rude
but, for all we know so far, he is making a linear 30 LED audio level
detector using 10 green, 10 yellow and 10 red leds. AFAIK, he hasn't
mentioned anything about frequency detection yet. I could be wrong, but I
think he just wants independant control of 30 LEDs. Hopefully the OP will
tell us more.

"Anthony Fremont" <spam-not@nowhere.com> wrote in message

:-? He hasn't really mentioned that part yet. I don't mean to be
rude but, for all we know so far, he is making a linear 30 LED audio
level detector using 10 green, 10 yellow and 10 red leds. AFAIK, he
hasn't mentioned anything about frequency detection yet. I could be
wrong, but I think he just wants independant control of
30 LEDs. Hopefully the OP will tell us more.

OK -- I admit it -- I'm brain dead -- I'm on the tail end of an
all-nighter that I just had to pull for work

So -- to answer the question.. yes -- using any of the 40 pin AVR
chips, you can easily drive 30 individual LEDs with no external
circuitry except for current limiting resistors... the I/O ports on
the AVR can sink enough current for a single LED easily.

and if all he wants is level detection, thats a breeze too -- somehow
I got the impression he was trying to do a "color organ" from the
initial description.. not a level meter.

John Barrett wrote:
"Anthony Fremont" <spam-...@nowhere.com> wrote in message
He hasn't really mentioned that part yet. I don't mean to be
rude but, for all we know so far, he is making a linear 30 LED audio
level detector using 10 green, 10 yellow and 10 red leds. AFAIK, he
hasn't mentioned anything about frequency detection yet. I could be
wrong, but I think he just wants independant control of
30 LEDs. Hopefully the OP will tell us more.
OK -- I admit it -- I'm brain dead -- I'm on the tail end of an
all-nighter that I just had to pull for work :)

BTDT, no fun.

So -- to answer the question.. yes -- using any of the 40 pin AVR
chips, you can easily drive 30 individual LEDs with no external
circuitry except for current limiting resistors... the I/O ports on
the AVR can sink enough current for a single LED easily.

and if all he wants is level detection, thats a breeze too -- somehow
I got the impression he was trying to do a "color organ" from the
initial description.. not a level meter.

He really hasn't told us what he's building exactly, maybe it's a secret.

Haha hey guys.. this topic has turned into something larger than I
originally anticipated! How wonderful!
Anyway.. back to the task at hand. My intention is to have a red bank
with 10 LEDs.. which act as a level meter, connected to an audio

source which (like was mentioned before) will have any frequencies
above around 150-250 Hz cut off. Once the level reaches a certain

amount (say, to drive the 6th, 7th, or 8th Red LED) the
microcontroller switches to the next colour bank of LEDs.. so that it
is a level meter with 10 level divisions, that changes colour on the
beat (in theory )

I must admit that I have zero experience with microcontrollers, and I
expect the building time of this project to be long, with small pieces
completed at a time. Although, I have patience on my side, and with
the resources and helpful communities available to me on the net I am
confident about getting help.

If the AVR could directly drive 30 LEDs (Keeping in mind that it only
has power up to 10 at any one time) , is there an appropriate AVR that
could drive 10x25mA LEDs? (250mA, hmm.. perhaps?)