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Author Topic: 3w RGB color bar (BOM w/ TLC5940, Fets, UNL's  (Read 2732 times)
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cincinnati ohio
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With the ZXLD1360, can I directly connect pwm output from an 3ch RGB controller to the 1360?  They're not logiclevel (I think).  If I limit current to 300ma per color, could I then take the Blue from 3 of the RGB's connect to single 1360, do the same for RED, Green...thus needing only 6x1360s for a fixture with 6x3wRGB?  Aka, run colors in series to each 1360 chip separately.
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With the ZXLD1360, can I directly connect pwm output from an 3ch RGB controller to the 1360?  They're not logiclevel (I think).

http://www.diodes.com/datasheets/ZXLD1360.pdf

Yes, you can run the Open Collector PWM signals from your controller to the "ADJ" pin of the ZXLD1360.

  If I limit current to 300ma per color, could I then take the Blue from 3 of the RGB's connect to single 1360, do the same for RED, Green...thus needing only 6x1360s for a fixture with 6x3wRGB?  Aka, run colors in series to each 1360 chip separately.

Because you have Common Anode RGB devices you can't put them in series.  That means you need one ZXLD1360 and all its associated components for EACH color of EACH LED package.  If you buy separate R, G, and B LEDs you can put several in series and run the series off a single ZXLD1360.
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cincinnati ohio
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Thankyou John... that's right, can't do series with CA, I've read so much material I keep forgetting the basics, althought, is this regardless of the driver I use or is there a circuit build possible for CA in series?
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I'm afraid not, the nature of CA or CC is that the 3 LED's share either the anode or cathode. This means that it is impossible to wire them in series which would require separate cathodes or anodes per each colour so you could connect them to the next colour.

Hope that makes sense
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cincinnati ohio
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ah, I can see now how it would not be possible... which is why vendors use individual colors led in their washes, floods and bars as it is overall less expensive on the hardware side. I was wondering why RGB's are hardly used in out of the box led fixtures, although, it's just a bit more of a task when having multiple RGBs per fixture.  Alternatively, If I could use a multi-channel IC like the TLC5940 would probably be the preferred route, but, it would need to accept 3 pwm outputs from DMX RGB controller, not sure if it's possible.

In using a switching regulator per color per RGB, what's consider the best choice considering dimming to be important, does the zxld1360 suffice or what other IC's, Fets..etc  I know many others have gone this route so curious as to what would be the best /cost effective way... ULN2003,LM317...etc

I had a lapse,  here's what I would need to do with 1360, as stated by John....
" Yes, you can run the Open Collector PWM signals from your controller to the "ADJ" pin of the ZXLD1360."
« Last Edit: February 08, 2013, 10:15:50 pm by sjim » Logged

cincinnati ohio
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since my output from the 3chRGB controller... each color output ranging from 12v and below, I will need to regulate before connecting to the ADJ pin bc the zxld1360's ADJ pin max is +6v. It seems the only way to do so is use a NPN transistor so the 1360 only receives voltages from 0 to +6 volts, is this the correct way to do this?  In reading the specs, do I regulate the NPN operational at +6v or is it +2.5v (according to the DC voltage method) ?
+
(1360's specs)
Driving the ADJ input via open collector transistor
The recommended method of driving the ADJ pin and controlling the amplitude of the PWM waveform is to use a small NPN
switching transistor as shown below:
This scheme uses the 200k resistor between the ADJ pin and the internal voltage reference as a pull-up resistor for the
e.

• Drive with DC voltage (0.3V < VADJ < 2.5V) to adjust output current from 25% to 200% of
IOUTnom
• Drive with PWM signal from open-collector or open-drain transistor, to adjust output current.
• Adjustment range 25% to 100% of IOUTnom for f>10kHz and 1% to 100% of IOUTnom for f <
500Hz
• Connect a capacitor from this pin to ground to increase soft-start time. 
(Default soft-start time = 500µs. Additional soft-start time is approximately 500µs/nF)
« Last Edit: February 09, 2013, 03:14:47 am by sjim » Logged

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I will need to regulate before connecting to the ADJ pin bc the zxld1360's ADJ pin max is +6v.

No, because the outputs of the RGB controller are Open Collector and the zxld1360 datasheet says you can use an Open Collector signal directly.

"Open Collector" means the output pin is internally connected to the Collector of an NPN transistor.  When the NPN transistor is off the output pin is floating. When the NPN transistor is ON the pin is pulled to ground.  In those cases where you need a HIGH/LOW signal from an Open Collector output you must provide a pull-up resistor.

Since the zxld1360 accepts an Open Collector output as an input it must have an internal voltage source.
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cincinnati ohio
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Would I a pull-up in this scenario, like a 10k pull-up between ADJ and controller's output?   
would it be close to this model below?
(each color 350ma)

3ch RGB controller output1(12v >)  -> 10kpull-up -> Adj 
10kpullup -> c1=100nF -> Grnd

12v -> Vin -> Rsense(.1ohm) -> RGB(eg.Red) -> 47uH -> Lx

I think also it might better to the use the ZXLS1350(350ma) vs 1360(1a)
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Dubuque, Iowa, USA
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Would I a pull-up in this scenario, like a 10k pull-up between ADJ and controller's output?   
would it be close to this model below?
(each color 350ma)

3ch RGB controller output1(12v >)  -> 10kpull-up -> Adj 
10kpullup -> c1=100nF -> Grnd

The RGB controller output goes to the gate of an NPN transistor, the collector connects to the open collector output, and the emitter connects to GND.
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cincinnati ohio
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How about this config to drive 1x3wRGB (r=2.5v, b/g=3.5v) at 350ma per color

(eg. 3chRGB Controller output for Red(only) from 12vDC > 3ch RGB controller(each separate output to) > NPN > ZXLD1352

12v+ ----47k 5% .25w----\  prevent flicker when power on
R  -------10k -------------/ (gate) BC848(npn)-collector -> ADJ(zxld1352)
B                                   (emitter)--GND           
G

Grnd  ---- power grnd of zxld

Any better way or different part configurations for doing so?  The ZXLD1352 has 1000:1 dimming vs 100:1 for the 1350 (assuming would this give better dimming spectrum)
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cincinnati ohio
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Can anybody validate this design for a single 3w RGB using a mini 3 ch RGB controller, see attachment.


* 3RGB-single-led-connection 001.jpg (181.85 KB, 2300x1700 - viewed 23 times.)
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