3w common anode RGB LED circuit?
Hi all,
Does anyone have a link to a circuit diagram for a common anode led? Here are the specs:
Soooo, either a circuit that can sink current (I believe that is the correct terminology) or some way to isolate power between the 3 colors would be much appreciated.
Here is a link to the led I have: http://www.dealextreme.com/details.dx/sku.4530
Does anyone have a link to a circuit diagram for a common anode led? Here are the specs:
- Red: 2.5V ~ 3.0V, 350mA
- Green: 3.2V ~ 3.8V, 350mA
- Blue: 3.2V ~ 3.8V, 350mA
Soooo, either a circuit that can sink current (I believe that is the correct terminology) or some way to isolate power between the 3 colors would be much appreciated.
Here is a link to the led I have: http://www.dealextreme.com/details.dx/sku.4530
8
comments
|
Add Comment
|
sort by:
active |
newest |
oldest
Regarding:
That's not a description of a common anode in the case of LEDs. It's not possible to use separate supplies for each component LED if the anodes are connected.
Hmm, well, I built one each of the power supply in steps 10-11 here for each color: http://www.instructables.com/id/Circuits-for-using-High-Power-LED_s/
If I connect each driver to each color and then to the same power source, turning one color up turns them all up. If I connect them to separate power sources they work individually. *shrug* I understand why - there's nothing to prevent the current from traveling through the other two leds, but don't know how to change it.
Are you saying that I should be using only one voltage regulator and then different resistors/current limiting methods for each led?
Thanks for the sugestions.
That's not a description of a common anode in the case of LEDs. It's not possible to use separate supplies for each component LED if the anodes are connected.
Hmm, well, I built one each of the power supply in steps 10-11 here for each color: http://www.instructables.com/id/Circuits-for-using-High-Power-LED_s/
If I connect each driver to each color and then to the same power source, turning one color up turns them all up. If I connect them to separate power sources they work individually. *shrug* I understand why - there's nothing to prevent the current from traveling through the other two leds, but don't know how to change it.
Are you saying that I should be using only one voltage regulator and then different resistors/current limiting methods for each led?
Thanks for the sugestions.
Dec 16, 2008. 10:30 AMgmoon
says:
Yeah, the real issue is that you've chosen two circuits; each one requires a path through the anode to regulate properly. I.E., the regulator's output pins are the anode itself. But the anode is shared. So if one regulator is "turned down," the others sense the change and compensate. The methods in steps 6,7,8 and 9 should work. They limit the current on the cathode side. The anode is fixed at V+. Any other connections in those steps are biasing resistors...
If I could ask you one more question ... If I end up doing PWM for this thing, do I have to mess with voltage and amperage much or can I keep them to acceptable levels through keeping the modulation short? Or would it just be best to drop all of the input power through a voltage regulator so that I know what it voltage and amperage I'm getting and then add small resisters to keep the amperage from running away from me? Thanks again for the advice :)
Dec 17, 2008. 4:42 AMgmoon
says:
Most of the solutions in the "High-Power LEDs" 'ible are current limiting--the LED driver is taking care of it. Look at Step 8. It's connected to a microcontroller (or any other PWM device.) The PWM itself is a square wave--the PWM effects are a function of the width and duration of the pulse. No voltage worries...
That's what I thought - time to break out an atmel programmer - thanks!
Cool, thanks! That will give me something to pick at. I have a great project to use it for, but don't like the way I have to set things up the way it is now.
If I could ask you one more question ... If I end up doing PWM for this thing, do I have to mess with voltage and amperage much or can I keep them to acceptable levels through keeping the modulation short? Or would it just be best to drop all of the input power through a voltage regulator so that I know what it voltage and amperage I'm getting and then add small resisters to keep the amperage from running away from me? Thanks again for the advice :)
Dec 16, 2008. 7:06 AMgmoon
says:
Any NPN transistor switching setup in common emitter mode should work. I.E., where the loads (LED cathodes) are each connected to a different NPN collector--one transistor per cathode (and one current-limiting resistor, too.)
I'm sure an FET would work, too. But you'll need some type of transistor switching, since the power requirements are high.
Regarding:
but I have to use totally isolated power supplies (i.e. one separate battery for each color).
That's not a description of a common anode in the case of LEDs. It's not possible to use separate supplies for each component LED if the anodes are connected.
I'm sure an FET would work, too. But you'll need some type of transistor switching, since the power requirements are high.
Regarding:
but I have to use totally isolated power supplies (i.e. one separate battery for each color).
That's not a description of a common anode in the case of LEDs. It's not possible to use separate supplies for each component LED if the anodes are connected.
 |
Vancouver Mini Maker Faire 2012
Rebuilding NordicTrack ski machine drive rollers
Looking for New Zealand-based Instructables authors for conference on August 27 in Wellington
Call to makers - Brighton Mini Maker Faire
Milk Crates - not as green as you think
TEDxBaghdad - Iraq - violence, dust storms and open sourced manufacturing
UK Mini Maker Faire - The Derby Silk Mill - New Poster to Share!
