RGB Led Control
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Posts: 46,084
I've got 3 rgb led's here which i can easily control by just hooking
it up to the pins from the stamp, however I'm looking for some way to
vary the voltage going out (so i can do different shades of
red/blue/green). Is there any easy way to do this with an external
chip or something?
Thanks,
Nathan
it up to the pins from the stamp, however I'm looking for some way to
vary the voltage going out (so i can do different shades of
red/blue/green). Is there any easy way to do this with an external
chip or something?
Thanks,
Nathan
Comments
to the LED.
Michael Clark Phone: (919) 468-9901 ext. 101
IVC, Inc. mdc@i...
>
Original Message
> From: immolation@h... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=BDcGY7JPApqaVTSsPQLgioTmovQyhPkyzc_S9CywuCM5oEVZX1fjlB2GdmyoZP3IFMqf7TiO7p-sfPujWA]immolation@h...[/url
> Sent: Thursday, April 26, 2001 6:24 AM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] RGB Led Control
>
>
> I've got 3 rgb led's here which i can easily control by just hooking
> it up to the pins from the stamp, however I'm looking for some way to
> vary the voltage going out (so i can do different shades of
> red/blue/green). Is there any easy way to do this with an external
> chip or something?
>
> Thanks,
> Nathan
>
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>Would PWM do the trick? You might need a cap to provide an average voltage
>to the LED.
Yes, if you could assign three independent PWM values... And since you
can't do this easily with the stamp by itself, the simplest way I can
think of to do this with a Stamp is to use 3-OpAmps or comparators.
First you must have a "triangle" or "saw" wave feeding into the inverting
input of each Op-Amp set as your PWM base frequency. Second, for each
non-inverting input you connect to a Stamp Pin through a series resistor,
and a capacitor tied to GND.
ie.
circuit X3 for Red, Blue, and Green
R
Stamp I/O >
/\/\----o
> to non-inverting input
|
o--||--> GND
C
Now, with this setup, you apply a PWM signal through the Stamp pin
to set an appropriate voltage level to the non-inverting Op-Amp input.
The result of combining this voltage level with a triangle wave through
an Op-Amp is a PWM signal with a duty cycle proportional to the input
voltage and a frequency equal to that of the triangle wave applied.
Note: - You will still need to update the stamp output regularly, but the
R-C stage will buy you the time necessary to perceive a simultaneous
multi-channel PWM control.
- For this application, you don't really need an elaborate triangle
or saw wave.
R
o--/\/\--o
| |
| 1|\ 2 |
o--| \o--o 1/6th of a 74HC14
| |/
|
o---||--->GND
| C
|
o
> pseudo triangle wave output
...you could even get tricky and produce a triangle wave with
a 4th Comparator and use a SINGLE LM324 if you set one up to
oscillate in a similar fashion.
> >
> > I've got 3 rgb led's here which i can easily control by just hooking
> > it up to the pins from the stamp, however I'm looking for some way to
> > vary the voltage going out (so i can do different shades of
> > red/blue/green). Is there any easy way to do this with an external
> > chip or something?
> >
> > Thanks,
> > Nathan
Beau Schwabe IC Mask Designer
National Semiconductor Network Products Division
500 Pinnacle Court, Suite 525 Mail Stop GA1 Norcross, GA 30071
the visual persistence will make the LEDs look brighter or dimmer depending
on the duty cycle. We have several customers that use the PAK-V to simulate
different light effects using either LEDs or drivers and stage lights.
With 8 channels, you could control 2 sets of RGBs and still have 2 spare
channels.
http://www.al-williams.com/awce/pak5.htm
Regards,
Al Williams
AWC
* Control 8 servos at once: http://www.al-williams.com/awce/pak8.htm
>
Original Message
> From: Beau Schwabe [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=lpsbMMcjZ1fu6jGlsa-91T2fWQdQLuKx2ALYnTSXANMmdwRoqksq3b8VmVM8uCNt33UemjzkbfeBR0P98_lYrg]bschwabe@a...[/url
> Sent: Thursday, April 26, 2001 9:49 AM
> To: basicstamps@yahoogroups.com
> Subject: RE: [noparse][[/noparse]basicstamps] RGB Led Control
>
>
> At 08:12 AM 4/26/01 -0400, you wrote:
> >Would PWM do the trick? You might need a cap to provide an
> average voltage
> >to the LED.
>
> Yes, if you could assign three independent PWM values... And since you
> can't do this easily with the stamp by itself, the simplest way I can
> think of to do this with a Stamp is to use 3-OpAmps or comparators.
> First you must have a "triangle" or "saw" wave feeding into the inverting
> input of each Op-Amp set as your PWM base frequency. Second, for each
> non-inverting input you connect to a Stamp Pin through a series resistor,
> and a capacitor tied to GND.
>
> ie.
>
> circuit X3 for Red, Blue, and Green
>
> R
> Stamp I/O >
/\/\----o
> to non-inverting input
> |
> o--||--> GND
> C
>
>
> Now, with this setup, you apply a PWM signal through the Stamp pin
> to set an appropriate voltage level to the non-inverting Op-Amp input.
> The result of combining this voltage level with a triangle wave through
> an Op-Amp is a PWM signal with a duty cycle proportional to the input
> voltage and a frequency equal to that of the triangle wave applied.
>
> Note: - You will still need to update the stamp output regularly, but the
> R-C stage will buy you the time necessary to perceive a
> simultaneous
> multi-channel PWM control.
>
> - For this application, you don't really need an elaborate triangle
> or saw wave.
>
> R
> o--/\/\--o
> | |
> | 1|\ 2 |
> o--| \o--o 1/6th of a 74HC14
> | |/
> |
> o---||--->GND
> | C
> |
> o
> pseudo triangle wave output
>
>
> ...you could even get tricky and produce a triangle wave with
> a 4th Comparator and use a SINGLE LM324 if you set one up to
> oscillate in a similar fashion.
>
> > >
> > > I've got 3 rgb led's here which i can easily control by just hooking
> > > it up to the pins from the stamp, however I'm looking for some way to
> > > vary the voltage going out (so i can do different shades of
> > > red/blue/green). Is there any easy way to do this with an external
> > > chip or something?
> > >
> > > Thanks,
> > > Nathan
>
>
> Beau Schwabe IC Mask Designer
> National Semiconductor Network Products Division
> 500 Pinnacle Court, Suite 525 Mail Stop GA1 Norcross, GA 30071
>
>
>
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
The combination of Stamp PWM and an op-amp providing proportional
current-source (sink) drive to the leds would be versatile, because
the stamp could be doing other things while the external circuitry
holds on to the current color combination. Current sink drive, 0 to
20 milliamps for PWM from 0 to 100%:
+9
100k |\| ;----|<---+9
stamp PWM --/\/\--o----|+\ |/ led, common anode
| | >---| 3904
.1 === ;-|-/ |\>
| | |/ | |
Vss | Vss | 250
`
o--/\/\--Vss
LM324 (four op amps in one dip)
circuit x3 for 3 leds.
Al's Pak chip does multiple PWM channels would be another solution.
Just for fun, build DIY time division mux, no external circuit
required except for current limiting resistors...
' common cathode leds active high on p0,p1,p2
outA=%000
loop: '
pulsout 0,2500 ' 5 millisecond on
pulsout 1,2500
pulsout 2,2500
goto loop
To get approximately equal drive to all the colors. Adjust the
current limiting resistors to compensate for time division mux.
Adjust pulse times for different colors. It is a full time job for
the stamp. An effect:
' leds active high on p0,p1,p2
outA=%000
i var word
loop:
i=i+1
pulsout 0,abs sin i *20
pulsout 1,abs cos i *20
pulsout 2,abs sin (i/4) *20
goto loop
-- regards,
Tracy Allen
electronically monitored ecosystems
http://www.emesystems.com
increases their life span.
On Thu, 26 Apr 2001, Al Williams wrote:
> A PAK-V will control LEDs in this way. You shouldn't even need the RC since
> the visual persistence will make the LEDs look brighter or dimmer depending
> on the duty cycle. We have several customers that use the PAK-V to simulate
> different light effects using either LEDs or drivers and stage lights.
>
> With 8 channels, you could control 2 sets of RGBs and still have 2 spare
> channels.
>
> http://www.al-williams.com/awce/pak5.htm
>
> Regards,
>
> Al Williams
> AWC
> * Control 8 servos at once: http://www.al-williams.com/awce/pak8.htm
>
>
> >
Original Message
> > From: Beau Schwabe [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=7GhyLIkZwVHH6MabcULHZjkWiOq6xx7m1ogHqbCtLY7uSGGrq0qhk08iekNN5i0ITZ5lOX8lKwyy0F5CEFRBkJVosA]bschwabe@a...[/url
> > Sent: Thursday, April 26, 2001 9:49 AM
> > To: basicstamps@yahoogroups.com
> > Subject: RE: [noparse][[/noparse]basicstamps] RGB Led Control
> >
> >
> > At 08:12 AM 4/26/01 -0400, you wrote:
> > >Would PWM do the trick? You might need a cap to provide an
> > average voltage
> > >to the LED.
> >
> > Yes, if you could assign three independent PWM values... And since you
> > can't do this easily with the stamp by itself, the simplest way I can
> > think of to do this with a Stamp is to use 3-OpAmps or comparators.
> > First you must have a "triangle" or "saw" wave feeding into the inverting
> > input of each Op-Amp set as your PWM base frequency. Second, for each
> > non-inverting input you connect to a Stamp Pin through a series resistor,
> > and a capacitor tied to GND.
> >
> > ie.
> >
> > circuit X3 for Red, Blue, and Green
> >
> > R
> > Stamp I/O >
/\/\----o
> to non-inverting input
> > |
> > o--||--> GND
> > C
> >
> >
> > Now, with this setup, you apply a PWM signal through the Stamp pin
> > to set an appropriate voltage level to the non-inverting Op-Amp input.
> > The result of combining this voltage level with a triangle wave through
> > an Op-Amp is a PWM signal with a duty cycle proportional to the input
> > voltage and a frequency equal to that of the triangle wave applied.
> >
> > Note: - You will still need to update the stamp output regularly, but the
> > R-C stage will buy you the time necessary to perceive a
> > simultaneous
> > multi-channel PWM control.
> >
> > - For this application, you don't really need an elaborate triangle
> > or saw wave.
> >
> > R
> > o--/\/\--o
> > | |
> > | 1|\ 2 |
> > o--| \o--o 1/6th of a 74HC14
> > | |/
> > |
> > o---||--->GND
> > | C
> > |
> > o
> pseudo triangle wave output
> >
> >
> > ...you could even get tricky and produce a triangle wave with
> > a 4th Comparator and use a SINGLE LM324 if you set one up to
> > oscillate in a similar fashion.
> >
> > > >
> > > > I've got 3 rgb led's here which i can easily control by just hooking
> > > > it up to the pins from the stamp, however I'm looking for some way to
> > > > vary the voltage going out (so i can do different shades of
> > > > red/blue/green). Is there any easy way to do this with an external
> > > > chip or something?
> > > >
> > > > Thanks,
> > > > Nathan
> >
> >
> > Beau Schwabe IC Mask Designer
> > National Semiconductor Network Products Division
> > 500 Pinnacle Court, Suite 525 Mail Stop GA1 Norcross, GA 30071
> >
> >
> >
> >
> >
> >
> > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
> >
>
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
Sean T. Lamont, CTO / Chief NetNerd, Abstract Software, Inc. (ServNet)
Seattle - Bellingham - Vancouver - Portland - Everett - Tacoma - Bremerton
email: lamont@a... WWW: http://www.serv.net
"...There's no moral, it's just a lot of stuff that happens". - H. Simpson
I'm interested to understand why this might be. Any references? (not
challenging you .... I just don't understand it)
Mike
At 10:48 AM 4/26/2001 -0700, you wrote:
>I'm pretty sure that pulsing LED's vs. supplying continuous voltage
>increases their life span.
_________________________________
Mike Walsh
walsh@i...
> I've got 3 rgb led's here which i can easily control by just
hooking
> it up to the pins from the stamp, however I'm looking for some way
to
> vary the voltage going out (so i can do different shades of
> red/blue/green). Is there any easy way to do this with an external
> chip or something?
>
> Thanks,
> Nathan
Actually you can do this with some software trickery in the stamp,
assuming your stamp has nothing else to do with its time. Just turn
all three on at the same time and set up three counters with three
different values. Count down each counter in a loop and when each one
reaches zero, turn the output off. After some predetermined length of
time (using a fourth counter), repeat the cycle by turning all three
on again. Basically you are doing PWM on three points in software.
Only thing is, you have to do it pretty fast or the LEDs will blink
visibly, so your stamp probably can't do anything else while all this
is going on.
Or, you can use one of our coprocessors or one of the other PWM
coprocessors available on the market to do the PWM for you while your
stamp goes on its merry way doing other things.
Chuck Davis
Oak Tree Systems
www.oaktreesystems.com
> --- In basicstamps@y..., immolation@h... wrote:
> > I've got 3 rgb led's here which i can easily control by just
> hooking
> > it up to the pins from the stamp, however I'm looking for some
way
> to
> > vary the voltage going out (so i can do different shades of
> > red/blue/green). Is there any easy way to do this with an
external
> > chip or something?
> >
> > Thanks,
> > Nathan
>
> Actually you can do this with some software trickery in the stamp,
> assuming your stamp has nothing else to do with its time. Just turn
> all three on at the same time and set up three counters with three
> different values. Count down each counter in a loop and when each
one
> reaches zero, turn the output off. After some predetermined length
of
> time (using a fourth counter), repeat the cycle by turning all
three
> on again. Basically you are doing PWM on three points in software.
> Only thing is, you have to do it pretty fast or the LEDs will blink
> visibly, so your stamp probably can't do anything else while all
this
> is going on.
>
> Or, you can use one of our coprocessors or one of the other PWM
> coprocessors available on the market to do the PWM for you while
your
> stamp goes on its merry way doing other things.
>
> Chuck Davis
> Oak Tree Systems
> www.oaktreesystems.com
Hmm sounds like my best bet, the stamp isnt going to be doing anymore
major asides from driving an lcd/some relay's neither of which will
be contantly changing, just occasionally
All those other people lost me in advanced electronics which i know
absolutely nothing about