I need at least 5W of power, more better.
This is for RGBW led.
I was told there is no way to digitally control LM338 etc.
I would use LM338, but the resistor to control current must be power potentiometer of very low resistance and these are not cheap
I would use LM338, but the resistor to control current must be power potentiometer of very low resistance and these are not cheap
+2 smile
Would you be happy with a circuit where the constant current could be controlled by a normal potentiometer.
If so, there is a simple circuit that would do the job
I would use LM338, but the resistor to control current must be power potentiometer of very low resistance and these are not cheap
+2 smile
Would you be happy with a circuit where the constant current could be controlled by a normal potentiometer.
If so, there is a simple circuit that would do the job
No POT will not work, I already made LM338 current circuit with 2.2Ohm resistor for 1.90Eur instead of paying 80Eur or 100Eur. Are you guys find it also crazy that in US and Europe the wireqound POTS are crazy expensive? Why? Nichrome wire is nonexistent in these parts of the world or is made from gold?
Umm, you didn’t understand what (s)he’s offering. Nobody is suggesting directly running the power through a pot. They were asking if you can do without the Arduino and just use a pot for control, in which case there are simple circuits where you control the constant-current source with a normal pot.
+2 smile
Would you be happy with a circuit where the constant current could be controlled by a normal potentiometer.
If so, there is a simple circuit that would do the job
Look, spec is asking if a circuit controlled by a pot (instead of Arduino) would suffice for your purposes. You just have to say “yes” or “no.”
Do not offer specialized LED controllers as these are not linear but square wave 180KHz etc.
Could you explain why you can't use a PWM/square wave drive in this case?
That said, there are quite a few LED controllers out there which are linear, just search for 'linear led driver'. Without knowing more about your application I can't really be more specific.
You mention that you need 5W. But at what voltage? What current? Are you driving chains of these, or is it a single LED? Are you going to want many of these drivers or just one big one (per color)?
QuoteCould you explain why you can't use a PWM/square wave drive in this case?
I cant use PWM because the this is backlight for a camera, and as such the flicker will be registered even if the eye do not see any. Because the LED will be RGBW I need to vary the colors so they can be in a state were they are very low intensity, PWM would introduce flicker in such scenario.
QuoteThat said, there are quite a few LED controllers out there which are linear, just search for 'linear led driver'. Without knowing more about your application I can't really be more specific.
Well I somehow never found any of these.
QuoteYou mention that you need 5W. But at what voltage? What current? Are you driving chains of these, or is it a single LED? Are you going to want many of these drivers or just one big one (per color)?
I wanted to use a single RGBW LED 5W or 10W, I posted a link to datasheet for CREE LED. It's somehow I missed that it is only 80CRI and I need like 95 or better CRI. Looked at digikey or mouser I see no RGBW LEDS with 95CRI
Well, using RGB to tweak the light is going to ruin the CRI anyway. I’d use separate RGB LEDs and choose really good white LEDs for the white — if you really need good CRI with color temp control, get high-CRI LEDs in a few color temps and dim between them.
Well PWM gets slow at low brightness, that is how it dims the light. At such conditions the camera detects flicker or image distortions at pixel level, especially if I would use R,G,B as separate photos then merge them together to make color image.
So if there is no RGBW chip with 95CRI white then this idea will not work. I need to have 2 chips one with RGB the other with 95CRI white at 3000K or 4000K, perhaps both. That complicates things, are you sure there is no RGBW chip with 95CRI white?
So is there any constant current linear not PWM LED drivers that can be controlled by say voltage 0V-3V or PWM from arduino for my task.