How to build 3 output sine wave generator...

[Impmon]

For an RGB LED? I wanted something that can make the LED cycle from
red to orange to yellow, green, blue, purple and back to red.

It would be a matter of building a generator with 33% duty cycle, and
each output are 120 degree off set from each other. Red is typical
2v, max 2.4v, both green and blue are typical 3, max 3.8. 4 leds,
common cathode and 3 anodes (one each color)

Since it'd be built into my PC, the source volt can be 5 or 12v.
Probably 12v since the PS has 40A max output. 2 HD's, 1 DVD burner,
cheap video card, and P4 CPU isn't anywhere near half that.

Any suggestion? I'm better at building digital circuits than analoug
circuits. I originally thought somehow using the 4017 counter, a few
diodes, and something to turn square to sine wave but like I said
analoug is my weak point. I'll probably use a transistor to drive the
LED directly so I could handle a few LEDs placed around the PC case
and have them run in synch.

 

[Johnny Boy]

For an RGB LED? I wanted something that can make the LED cycle from
red to orange to yellow, green, blue, purple and back to red.

It would be a matter of building a generator with 33% duty cycle, and
each output are 120 degree off set from each other. Red is typical
2v, max 2.4v, both green and blue are typical 3, max 3.8. 4 leds,
common cathode and 3 anodes (one each color)

Since it'd be built into my PC, the source volt can be 5 or 12v.
Probably 12v since the PS has 40A max output. 2 HD's, 1 DVD burner,
cheap video card, and P4 CPU isn't anywhere near half that.

Any suggestion? I'm better at building digital circuits than analoug
circuits. I originally thought somehow using the 4017 counter, a few
diodes, and something to turn square to sine wave but like I said
analoug is my weak point. I'll probably use a transistor to drive the
LED directly so I could handle a few LEDs placed around the PC case
and have them run in synch.

I'm probably missing something, but why sine wave?

.... Johnny

 

[James Thompson]

For an RGB LED? I wanted something that can make the LED cycle from
red to orange to yellow, green, blue, purple and back to red.

It would be a matter of building a generator with 33% duty cycle, and
each output are 120 degree off set from each other. Red is typical
2v, max 2.4v, both green and blue are typical 3, max 3.8. 4 leds,
common cathode and 3 anodes (one each color)

Since it'd be built into my PC, the source volt can be 5 or 12v.
Probably 12v since the PS has 40A max output. 2 HD's, 1 DVD burner,
cheap video card, and P4 CPU isn't anywhere near half that.

Any suggestion? I'm better at building digital circuits than analoug
circuits. I originally thought somehow using the 4017 counter, a few
diodes, and something to turn square to sine wave but like I said
analoug is my weak point. I'll probably use a transistor to drive the
LED directly so I could handle a few LEDs placed around the PC case
and have them run in synch.

You can get the RGB leds that have built in chips to do that and I think
they run on 5 volt. It would just be a matter of connecting them in parallel
to go around your case.

 

[Deefoo]

For an RGB LED? I wanted something that can make the LED cycle from
red to orange to yellow, green, blue, purple and back to red.

It would be a matter of building a generator with 33% duty cycle, and
each output are 120 degree off set from each other. Red is typical
2v, max 2.4v, both green and blue are typical 3, max 3.8. 4 leds,
common cathode and 3 anodes (one each color)

Since it'd be built into my PC, the source volt can be 5 or 12v.
Probably 12v since the PS has 40A max output. 2 HD's, 1 DVD burner,
cheap video card, and P4 CPU isn't anywhere near half that.

Any suggestion? I'm better at building digital circuits than analoug
circuits. I originally thought somehow using the 4017 counter, a few
diodes, and something to turn square to sine wave but like I said
analoug is my weak point. I'll probably use a transistor to drive the
LED directly so I could handle a few LEDs placed around the PC case
and have them run in synch.

If you really want sines (PWM would probably be better) and you are not too
picky about the quality you can easily generate three sines with 120 degree
phase difference using shift registers and resistors. See here for instance
http://www.edn.com/index.asp?layout=article&articleid=CA6321527

BTW, what's your circuit for? To beautify your PC?

--DF

 

[Michael A. Terrell]

For an RGB LED? I wanted something that can make the LED cycle from
red to orange to yellow, green, blue, purple and back to red.

It would be a matter of building a generator with 33% duty cycle, and
each output are 120 degree off set from each other. Red is typical
2v, max 2.4v, both green and blue are typical 3, max 3.8. 4 leds,
common cathode and 3 anodes (one each color)

Since it'd be built into my PC, the source volt can be 5 or 12v.
Probably 12v since the PS has 40A max output. 2 HD's, 1 DVD burner,
cheap video card, and P4 CPU isn't anywhere near half that.

Any suggestion? I'm better at building digital circuits than analoug
circuits. I originally thought somehow using the 4017 counter, a few
diodes, and something to turn square to sine wave but like I said
analoug is my weak point. I'll probably use a transistor to drive the
LED directly so I could handle a few LEDs placed around the PC case
and have them run in synch.

LEDs are not linear devices. Sine waves won't work.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Impmon]

You can get the RGB leds that have built in chips to do that

and I think they run on 5 volt. It would just be a matter of
connecting them in parallel to go around your case.

Yes I am aware of that but they are often single LED and when I
replace the 6 static LED in my computer case with the RGB LED, they
won't be able to stay in synch with each other. I wanted all LED to
shine the same color at the same time.

I'm probably missing something, but why sine wave?

I wanted gradual change in color. I could do a version with square
waves in 6 steps total but I'd get EGA-esque colors only.

If you really want sines (PWM would probably be better) and you
are not too picky about the quality you can easily generate three
sines with 120 degree phase difference using shift registers and
resistors. See here for instance

http://www.edn.com/index.asp?layout=article&articleid=CA6321527

I'll have to take a look in that one.

BTW, what's your circuit for? To beautify your PC?

My computer case came with 2 "bubble" tubes running vertical on the
front of the case. Right now it's fixed at blue only and has a total
of 6 (3 on each side) and I wanted to change it to color cycling RGB
LED to fake a music box. Just pointless eye candy, one that probably
hasn't been commercially sold yet. The color changing tubes I could
find were all flashing or choppy, no guadual color shifting.

LEDs are not linear devices. Sine waves won't work.

Yes. Just got that. So I'd have to come up with PWM circuit.

What I wanted to try involves having red start at full peak. Then
bring the green up gradually till at max brightness, dim the red,
bring blue up, dim the green, and then brighten red and finally dim
blue to continue with the cycles.

 

[jasen]

For an RGB LED? I wanted something that can make the LED cycle from
red to orange to yellow, green, blue, purple and back to red.

They may make 'em like that...

It would be a matter of building a generator with 33% duty cycle, and
each output are 120 degree off set from each other. Red is typical
2v, max 2.4v, both green and blue are typical 3, max 3.8. 4 leds,
common cathode and 3 anodes (one each color)

you'll need more than 33% duty cycle.

R red
RG yellow
G green
GB cyan
B blue
R B magenta

but that's not quite whay you asked for.

to get orange you need to run the green at a lower power to the blue,

Any suggestion? I'm better at building digital circuits than analoug
circuits. I originally thought somehow using the 4017 counter, a few
diodes, and something to turn square to sine wave

you're wanting to fade between colours that makes a difference...

since you're competent with digital I'd suggest using a microcontroller
to PWM the LEDs, LEDs respond well to pulse-width modulation, much better
than they do to a variable voltage, (where as you note different colours
want different voltages)

I'll probably use a transistor to drive the
LED directly so I could handle a few LEDs placed around the PC case
and have them run in synch.

It would be a matter of building a generator with 33% duty cycle, and
each output are 120 degree off set from each other. Red is typical
2v, max 2.4v, both green and blue are typical 3, max 3.8. 4 leds,
common cathode and 3 anodes (one each color)

Since it'd be built into my PC, the source volt can be 5 or 12v.
Probably 12v since the PS has 40A max output. 2 HD's, 1 DVD burner,
cheap video card, and P4 CPU isn't anywhere near half that.

unfortunately these three-in-one leds don't go well in series (that common
cathode gets in the way) so there's no advantage so using 12V,

5V would be more efficient, but you can do 12V instead it's unlikely to be a
signiificant load either way.

Any suggestion? I'm better at building digital circuits than analoug
circuits. I originally thought somehow using the 4017 counter, a few
diodes, and something to turn square to sine wave but like I said
analoug is my weak point.

you could maybe do that put a large-ish capacitor parallel with each LED and
some of the bias resistor...

you'd need this three times once for each colour


0V --+---|<---[22OR]--+-[330R]----. .---- +12
| | \ /
| ||+ | _\| /
`-----||---------' ---+---
|| 1000uF |
|
digital in -[2K2]-'

that'd be OK with one LED
but with a bunch you end up needing many capacitors...

hmm....

+12 ----------------+
|
|
| /
in |/
--[1K]--+--[1K]--|
| |\|
| |~\
| |
| 470uF [560R]
----- |
----- \|/
| ---
| |
0V ---+-----------+


That'd probably work better but with many LEDs you'd need a heatsink on the
transistor.

Otherwise if you want to use my suggestion of PWM,
It'd make a good first microcontroller project.


Bye.
Jasen

 

[Studio271]

Just a quick link: http://www.uni-bonn.de/~uzs159/triphase.html

Voltage-controlled 3-phase sine-wave oscillator, could probably be
easily modified (resistors, anyone?) to drive an RGB LED.

-Drew