ws2801 how do they work ?

[david_1]

http://www.alibaba.com/product-gs/48...ip_ws2801.html

my long post vanished :-(

[david_1]

I would like to make a star out of above link 32leds per meter.
500mm in lenth 8 arms = 128 leds with a few in the centre hub

should look quite nice but I need a little help on how the ws2801 work anyone want to help me a little ?
like how can I control each led in the arm ? see it sounds so simple..

David

[Lefserev]

Well, to take the first stab at it, anybody feel free to correct me since I am new to this. The WS2801 chips are designed to drive a tricolor(RGB) LED and connect from one to another in a long chain. According to SparkFun, http://www.sparkfun.com/products/10444, the chips receive data from 2 wires take away the data they need and pass the remaining bits and bytes to the next chip in line. Each string of smart chips requires 4 wires:positive low voltage power, neutral power, clock data input, and serial gray scale data input. With the power and inputs, 3 LEDs can be driven with each chip (typically red, green, and blue)
The pixel or smart LED strings are usually controlled by either the e680 or e681 controller through the e1.31 dmx over ethernet protocol.

I hope I covered enough. I too am considering doing something with pixels.

[david_1]

yes I read that too but I thought you clocked in 24 bits per chip so ten chips 240 bits...
but it would be first in first out so the last chip would end up with the first 24 bits and the first chip the last 24bits...
and having read data sheet all i then need to do is wait for 500us for data to be sent to leds...

but Thanks and thats sort of what i am trying to find out :-)

[David_AVD]

It is 24 bits per chip. The first chip will see the first 24 bits. I know that sounds wrong, but trust me that it's right. They are not conventional shift registers.

So, clock in your 24 * n bits (750 KHz max), then leave clock low for > 500us and they will latch the data.

[jstjohnz]

yes I read that too but I thought you clocked in 24 bits per chip so ten chips 240 bits...
but it would be first in first out so the last chip would end up with the first 24 bits and the first chip the last 24bits...
and having read data sheet all i then need to do is wait for 500us for data to be sent to leds...

but Thanks and thats sort of what i am trying to find out :-)

The chips start a new frame by looking for incoming data, but not passing it through. After the first chip in the chain has grabbed its 24 data bits, *then* it goes into "pass-through" mode. So the 2nd chip never sees bits 1-24, it's data stream starts with bits 25-48, which it grabs, then it goes into "pass-through" mode.

[david_1]

ah ok so I had it all wrong :-) many thanks for your kind words I will order 5meters now and see if I can make them dance :-)

many thanks for your help..

[david_1]

ok so Ive googled looking for a suppler of ws2801 strip lights...
can anyone send me a link to an easten type supplier of 5meter lenths please...

thanks

[JSS]

ok so Ive googled looking for a suppler of ws2801 strip lights...
can anyone send me a link to an easten type supplier of 5meter lenths please...

thanks

Try http://www.aliexpress.com/fm-store/7...0-SMD-RGB.html

[david_1]

well they arrived two 5 meter strips arrived, i cut off 15 leds for a test strip. They seem very easy to control I have
; BLUE GREEN RED if i turn on just one led in the 5050 package.
or light blue yellow purple if I turn on two leds
an white if i turn on all three.

The pwm setting for each led is from 0 to 255, 0 being off and 255 being fully on but anything over 100 seems to look the same, my thoughts are that I run out of current to increase brightness .

I can fade each light in and out, now im fading up to D'100' because this look ok and will save power over all.

all of this is done with a pic and assembler

anyone else working on these ? I have no clue about any of the protocals you guys use to control your displays or which I should try to emulate. I am building a single flashing star about 4 foot in size :-)

David