LED with SM16716 IC

newaisa

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I have got a string of 50 RGB LED with SM16716 chip in it. The seller told me that I do not need to have Voltage drop concern in this and just use a 5VDC power supply. Reason behind this is that the chip is able to maintain a +5V throughout the string. Is that true?


Any comment regarding the above statement?


My conventional LED connection(single color without any IC) would require me to take into account on voltage drop and add a resistor into a string.
 

fasteddy

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You are still bound by Ohms law so this statement cant be true. If the voltage drop is far enough that it drops below the forward voltage of the LED then it cant maintain its current draw and then will diminish in output as LEDs are current devices
 

lithgowlights

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Unless the chip has a small DC to DC converter. VERY unlikely I know, but I cant find much in English about this chip at all, so it will remain a mystery for a bit longer
 

lithgowlights

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In that case 5V is no drama as long as you use thick wire, good power supplies and limit the runs to 50 or so, unless you feed power both ends :)
 

fasteddy

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lithgowlights said:
In that case 5V is no drama as long as you use thick wire, good power supplies and limit the runs to 50 or so, unless you feed power both ends :)
That correct there is no issue using them except for the limited community controller support but as long as you take lithgowlights advice then you shouldnt have any issue unless the string cable is a very thin guage. But if you injected power inbetween each 50 pixels then you could easily run 150 or even a full universe of 170 pixels as one string depending on the controller you use.
 

TimW

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The 16716 seems to be 4 wire (unlike the 715). I think its closer to 2801 in protocol... (with some extra bits to distinguish data from reset patterns...
SM16716 is designed for LED lighting, point source applications
Design of the driver chip, the use of advanced high-voltage CMOS process, provides
Three-way constant current driver for modulating the output and gray, especially for discrete
Multi-grayscale full color lighting system.
SM16716 chip includes a serial shift register and cascaded drive
Dynamic circuits, data and control signals output by the internal drive to the post
The next level circuit.
Package diagram
Feature Description SOP16
 three-way drive output, maximum current of 60mA, the largest port
Pressure to 26V
 output constant current drivers using IN-RUSH structure, compatible with constant pressure
Drive mode, an external device can be converted to higher voltage or
The output drive current
 Built-in LDO voltage regulator circuit, power supply range of up to 3.3-7V,
 used by code from the token bus technology, two-lane shift, the shift
Clock up to 30MHz
 direct input 8-bit grayscale data, 256 PWM output
 Package: SOP16
My google translation suggests:
1 moved to 50bit first "0" as the start frame, and then moved into the data frame. Start frame and the frame is first moved to high. Each data bit
DCLK rising edge is fed into
2 1st data frame is moved from the side nearest the corresponding LED lights. The format includes: 1bit start bit "1" +3 group 8bit gray value
3. Turn into data points, plus the additional pulse corresponding points, the new data that came into effect; send additional pulse data signal is low
Flat
4 each grayscale data are "1" +24 BIT of data

... which gives you the basic idea!
 

newaisa

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Thanks for all the reply guys. I am using a separate controller and power supply.
As I have never used any chipped LED before, I would like to clarify, in this case I must use a 5V power supply?


I only know that normal LED string(chipless), I can use 12V,24V,48V on a string of LED as long as the resistor is correct for the right voltage distribution.


If I must have 5V power supply for the string, how is it possible for the 5V to support all the 50 LEDs?(I am taking voltage drop into consideration)
If what I asked does not make any sense, please correct me as I don't have much experience with electronics.


Right now I have a 5V 100W power supply. In this case if I use it on a string of 50 LEDs. What is the value of resistor I should be using?
 

j1sys

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Tim et al -
yes, i see that the SM16716 is very different. i saw the three different size chips on one of the sites and thought that it was just package/channel variations.
below is the link for the chinese spec page.
looks like a cross between the 2801 and 6803 protocol. it is 8 bit x 3 but they add a 1 bit in front to make each RGB equal 25 bits. Then if you send 50 0 bits in a row it is a reset. this is kind of like an 8 bit variant of the 6803 protocol which is 5x3 + 1 = 16 bit, 32 zeros = reset.
it will make it harder to implement in SPI hardware controllers not being an even 8 bit multiple but is doable like the TM180x weird pattern.
-Ed
http://www.tlshk.com.cn/UploadFile/UploadPhotos/2010111116356107.pdf
 

fasteddy

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newaisa said:
I only know that normal LED string(chipless), I can use 12V,24V,48V on a string of LED as long as the resistor is correct for the right voltage distribution.


If I must have 5V power supply for the string, how is it possible for the 5V to support all the 50 LEDs?(I am taking voltage drop into consideration)
If what I asked does not make any sense, please correct me as I don't have much experience with electronics.


Right now I have a 5V 100W power supply. In this case if I use it on a string of 50 LEDs. What is the value of resistor I should be using?
It looks like you may be confusing constant current with voltage.

RGB lighting that is dumb (no IC installed) uses a current limiting resitor to control the current flow based on the voltage supplied. This is not the best method for LEDs as a small difference in voltage can have a big effect on current (again Ohms Law). This method is sufficient for low powered LEDs but with High powered LEDs this can cause over heating issues and dramatically decreased life spans of the LED

The best method to control LEDs is current, as I mentioned before LEDs are current devices. The SM16716 IC you are using is a constant current IC, so as long as the voltage is above the forward voltage (plus some overhead) of the LED then the light should put out approx the same amount of light as it is maintaining the required current that the LED requires even though the voltage may have dropped

So the SM16716 IC controlled light that you have do not require a resistor, presuming you have a prebuilt string. All you need to do is hook it up to the controller. If you are actually building the RGB lights then thats a different kettle of fish as you do need a reference resistor to set the current of the IC output.

Now the 8mm RGB LEDs have a forward voltage of approx 2 Volts for Red, 3 Volts for Blue and Green. This means that due to the LEDs connected in series then you can only have 1 LED per circuit as 5v - 3v doesnt leave enough voltage for another LED unless they were connected in parrallel. So each LED is individual with its own IC and circuit, so if you loose 1 LED generally the rest wont go out (unless the IC failed) and all that is required is to cut the dead led/pixel out and reconnect and you will be back in action. They are not like traditional strings.

And yes you must use a 5vdc power supply as the IC and circuit is designed and rated to work within that range
 

newaisa

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Yeah...I was really confused. In the end I ordered the strips of 50 and simply use a 5V DC power supply with sufficient current and they work like charm!
It was simpler than I thought.Anyway thanks for all the explanations
 

bratmat

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HI I am new on this forum, and sorry for bad English :-(

I'm curious if someone on this forum knows how fast can be IC LED with the chip 16716. Few weeks ago I tried to use pixel led with the IC 6803 but it's very slow chip. I think it can only 20FPS. And I have a lot problems because my client want to use strobo effect with those leds, but they lost a lot of frames. They are connected to pc by DMX Decoder and works with Madrix software. Is it possible that leds on ic16716 will be much faster ?
 
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