New 12V smart pixels ——GS8208

queena

New elf
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Jul 20, 2020
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hey guys, I found a new kind of pixel--GS8208, and I do some test on it .It seems so interesting

Traditional 5V/12V smart pixels

5V smart pixels aren’t a good idea because they are non-uniform brightness. They can’t travel longer distance without further power requirements.

Therefore, a 12V + resistance smart pixels has been adopted. It is a bad idea to step down voltage from 12V source to 5V using resistor because the resistors will most likely burn up. The power dissipation is more than 5V smart pixels. 12V+R smart pixels can run more pixels together in a string without having to worry about voltage drop.

We can find the difference between voltage mode and current mode. The LED drive current change with VCC voltage for voltage control mode. So the brightness of LED will inevitably decline since it adopt voltage control mode. It should be only a temporary scheme.

图片1.png
New 12V smart pixels —— GS8208

At present, there are some new 12V smart pixel on the market. They adopt current mode LED control and do not use resistance voltage divider. When working under 12V source, the LED current is only 18mA. The new 12V smart pixels is uniform brightness with more pixels in a string.

Different structure comparison of two kinds of 12V smart pixels drive
图片2.jpg图片3.jpg


We have tried to analyze the control mode of the new 12V smart pixel. Different from the 5V one, the new 12V smart pixel adopt series LED structure. Three LED RGB are connected in series with 12V power source. The current is only 18mA.

4.jpg
For this series LED structure, when only one light is on, such as red light, S1 is disconnected, S2 / S3 / S4 is closed, current flows from red light to S2 / S3 / S4, green light and blue light are turn off. The current is 18mA. When the LED is fully on, S1 / S2 / S3 is disconnected and S4 is closed. The current flows from red light to green light to blue light and then flows through S4. The current is still 18mA. If the LED is off, S4 is disconnected and there is no current in the circuit. This new 12V smart pixel connects RGB in series, and controls the LED on and off by the switch in parallel. In normal operation, the current of 12V structure is always 18mA, so there is no heating problem. When the light is white, the power efficiency is even higher than 5V smart pixels.
图片5.png

We compare all these smart pixels in the following data.

5V smart pixel12V smart pixelNew 12V smart pixel
Power supply5V12V12V12V
Drive ICWs2811Ws2811GS8208GS8512
LED control modeCurrent modeVoltage modeCurrent modeCurrent mode
LED current55mA24mA18mA18mA
LED dissipation115mW-275mW120mW-288mW216mW216mW
maximum efficiency53%22%66%66%
LED structureparallelparallel+Rseriesseries
Transmission protocolReturn to zero codeReturn to zero coderedundant data transmissionDMX512
Gray scale256256409665536
It was found that these new 12V smart pixel have made a lot of improvement compared with the traditional products. The data transmission also adopts the redundant data transmission mode or DMX512 mode. It is more reliable to be used.

Generally speaking, the new 12V smart pixel have nothing to do with voltage drop over distance if you have a long distance string. So the power supply can be placed further away from the LED, which is convenient for installation. I believe this new 12V smart pixel really offers a better choice.
 

AAH

I love blinky lights :)
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I have often mentioned the GS8208 pixels when people are wanting to use 12V pixels. They have the benefits of the reduced need to look after the supply voltage compared to 5V and they are only about 18mA maximum at 12V compared to 55mA at 12V for WS2811. I have a few projects in the pipeline where the GS8208 will be my preferred pixel. When I get the time I had planned on doing a video showing input and output voltages and the currents of GS8208 vs 12V WS2811 strings.
 

algerdes

Al Gerdes
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I don't understand as to how when all three LEDs are burning, they only draw 18ma. It is very interesting that they do, just I'm not seeing how this is possible.
 

AAH

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I don't understand as to how when all three LEDs are burning, they only draw 18ma. It is very interesting that they do, just I'm not seeing how this is possible.
I haven't done the testing myself to see if there's a constant 18mA at all times or if the current varies from 0mA up to the maximum 18mA depending on the maximum brightness of any colour. The maximum current regardless is 18mA compared to 55mA for 2811.


What's the price comparison?
When I got a single string to play with it was a few dollars dearer than 5V 2811 nodes. I don't know what 12V 2811 nodes are worth but I expect there's little difference between 12V 2811 and 12 GS8208
 

TerryK

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The GS8208 (best as I can tell manufactured by Shenzhen Genesys-Systech) compares better to a WS2815. The GS8208 is mostly an enhanced WS2815.

Newstar LED has a GS8208/WS2815 comparison; here is the link:

I don't understand as to how when all three LEDs are burning, they only draw 18ma. It is very interesting that they do, just I'm not seeing how this is possible.
As David mentioned the LEDs are in series. To help explain, for all colors OFF, S4 is open and S1, S2, and/or S3 can be either open or closed. With S4 open, the other switches become 'don't care'. My bet is probably closed but the IC documentation does not indicate. When any color or colors are ON, S4 is closed and a combination of S1, S2, and/or S3 is PWM-ed open (actually MPWM-ed) [Say What? Yes that's in the documentation!]. One of the graphics shows Red ON and the switch positions can be seen. The current path is shown as a Red line. For Yellow, S1 and S2 would be MPWM-ed open according to the commanded intensity and S3 and S4 would be closed.

OK, what exactly is MPWM? As used in the GS8208 it is Multiple Pulse Width Modulation. The GS8208 documentation example uses a LED turned ON 16. A bit difficult to determine but it appears that is a command value of 16 of the possible 0 to 255 binary. The 16 is split into 4 pieces of 4 within the PWM time period. Again rather vague but the split to 4 likely is related to the 8KHz internal refresh oscillator. Outputs are also staggered, Green by 80ns and Blue by 160ns. The staggering of outputs and somewhat the MPWM serve to help minimize the V+ noise when the color modulator 'slams' one or more colors On.
 

algerdes

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The control is not my question, as unique as it is. The fact that an element (LED) has a draw, so turning 2 or 3 on at the same time should be 2 or 3 times that draw.
The comment about not knowing if the 18 mA is consistent, or if it is the max, makes the most sense. Checking to see if a single LED draws 18 mA or if it is a lesser amount might clear this up. (I'm betting on a lesser amount, but will wait for actual testing.)

Regardless, only 18 mA is a wonderful thought. If the color saturations are equivalent, and we can get the code into our controllers - then we have a win!
 

TerryK

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The control is not my question, as unique as it is. The fact that an element (LED) has a draw, so turning 2 or 3 on at the same time should be 2 or 3 times that draw.
The comment about not knowing if the 18 mA is consistent, or if it is the max, makes the most sense. Checking to see if a single LED draws 18 mA or if it is a lesser amount might clear this up. (I'm betting on a lesser amount, but will wait for actual testing.)

Regardless, only 18 mA is a wonderful thought. If the color saturations are equivalent, and we can get the code into our controllers - then we have a win!
If the LEDs are in parallel, yes; 2 LEDS ON would double the current assuming that each LED is passing the same amount of current. The LEDS for a GS8208 however are in series so if any 2 or all three LEDs are turned ON then each LED has the same current flowing through them. In series the LED current would not sum.
The device's staggered outputs and MPWM technique relative to commanded illumination of each color makes analysing the device complicated. The internal constant current source when ON sets the maximum current; 18 mA or whatever (not including the 'keep alive' current the logic needs).

It sounds a bit like you may be confusing the current through the LEDS, the voltage drop across, and the power being dissipated within them. I've already tested the WS2815s and I'd test the GS8208s too as I have a project in the schedule they would work well in. I have not yet found a good US source for the GS8208 and I have a terrible success rate when ordering from China.
 
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AAH

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A few questions because I haven't gotten around to testing and videoing the ones I bought last year.
1) If you lose 1 led out of the RGB does the pixel go dark with no colours shown or does it just show the other 2 colours.
2) With the data backup does the next pixel process it's own data or does it process the data from the previous "dead" pixel. In short if you have a matrix or similar do the lines stay in sync with 1 pixel missing or does the missing pixel cause everything downstream to shift 1 pixel.
3) On power up how long is it before the internal test function starts up and does it require the data signal to be open circuit, 0V or 5V to start the test signal.
4) Related to 3. Will the pixels resort to a test signal if they don't get a valid WS281x type signal for a given amount of time. This can be important if pixel controllers don't send data out at all times.
5) Does each chip produce the test signal or does the first pixel that doesn't see data and it gets sent out along the data lines?
6) If the first pixel produces the test signal is it sent out in a WS281x type signal?
7) The GS8208 runs off the same data signal as WS281x. Can the GS8208 be daisy chained in with WS281x pixels with the WS ones before and/or after? Worldsemi screwed around with their WS2811 timing and I was wondering if that has any effect on GS8208 pixels.
8) If you have the RGB brightness all set to 5 (out of 255) for instance is the current 18mA or closer to 1mA

<end questions>

These are all questions that I had intended to answer when I got some bare GS8208 pixels last year. Before I recommend something I like to know the answers to how it will perform and if someone calls me up with a problem at 11pm on 30th November with an issue.
 

marmalade

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nice tech but still very expensive at 50c per led... when a ws2811 can be had for 20c. Possibly could save $$ on power supply/cabling etc however.
 

AAH

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nice tech but still very expensive at 50c per led... when a ws2811 can be had for 20c. Possibly could save $$ on power supply/cabling etc however.
Where did you get that price from? Ray has them on his page for 23c each which works out at a massive saving compared to WS2811 in power and cabling. 1/3rd of the power usage of 12V WS2811 and at 1/3rd the current in a lot of cases there will be no need for heavy duty or possibly any power injection.
Not sure what anyone else is selling them for or what his non Ali price is like.
 
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