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Author Topic: WS2801 vs A6281  (Read 2850 times)
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Hello all,

I'm going to order some new stuff soon and I'm having trouble deciding between the WS2801 and A6281 3 channel LED drivers:

http://www.sparkfun.com/products/10444
http://www.allegromicro.com/en/Products/Part_Numbers/6281/

Primarily I like the A6281 because I can direct drive 12v LED strip with it (6 RGB 5050's), the WS2801 is pretty similar but I don't think I would be able to direct drive the strip with it, I would need transistors or something like that. My main problem with the A6281 is the price, its 2ish dollars depending on the quantity (most likely around 50) which comes out to $100ish which is just painful whereas I can get the WS2801 in the same quantity for about $35. The transistors would drive up the price a little bit but not that much, and also it would mean that I could power longer runs of the strip with the same setup but thats not a huge upside for my purposes.

The package isn't a concern because I'm going to reflow solder on custom etched boards either way I go.

The communication is pretty easy with both, but I think the A6281 wins in this respect by a little bit.

What do you guys think? Are you partial to one or the other?
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P.S. While looking at buying a couple hundred 5050 RGB leds I noticed something interesting. If you buy this strip:

http://www.kutop.com/waterproof-5-meters-72-watts-smd-5050-led-cool-pure-warm-white-blue-green-pink-red-yellow-orange-purple-rgb-300-leds-light-strip.html

The price is a fraction of what it would be if you bought component LEDs from websites like this one:

http://www.superbrightleds.com/moreinfo/component-leds/rgb-5050-smd-led-120-degree-viewing-angle/322/1254/

Granted 3 lots of 100 of the LEDs from ebay would be about the same cost as the strip in terms of LEDs but its already soldered onto a easy to use strip which can be cut every few inches. And if you want the component LEDs you could always get the non waterproof strip and just hot air rework them off one at a time.

I thought it was pretty interesting that it was the same price or even cheaper to buy the strip than the LEDs themselves. And that strip is incredibly cheap compared to the stuff sold by american websites which charge approx. 3 times as much. I plan to buy as much of it as I can before the price rises.
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Colorado
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I've been using the WS2801 for some time now, mainly because of cost, but also because I can hand solder them.  Couldn't do that with the A6281.  As for RGB LEDs, Cree ones are just ever so slightly cheaper than those 5050s, like 2 cents (at the >100 quantity) ...  Hit Mouser and search for '941-V6AFKBCKNPRGJ7A3' ...
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http://www.ebay.com/itm/100-pcs-RGB-PLCC-6-5050-3-CHIPS-SMT-SMD-LED-Light-/250922102177?pt=LH_DefaultDomain_0&hash=item3a6c1f6da1#ht_2921wt_962

These ones are pretty cheap, much better than both the Crees and the 5050s from that other site.
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Kctess5: The strips you linked to on kutop.com have no controller ICs and aren't RGB 5050 LEDs - hence their very low price.  Apples and oranges.

I've put the WS2801 and LPD8806 head to head.  The WS2801 uses beautiful full 24 bit.  However, although the max clock rate is 25mhz no one can get them to run reliably above 2mhz with more than a handful strung together.  There's a little snippet in the datasheet everyone seems to overlook that I believe explains it: The transmit the data over long distance by cascading, the WS2801 integrates push-pull output stage with strong driving capability which enables the data and clock can be transmitted up to 6 meters at 2MHz clock frequency. To prevent the reflection, it is necessary to connect a 50Ω resistor at the data input or output port for impedance match.


That said, the LPD8806 runs great at 8mhz for 5 meters (haven't tested longer) but there is no datasheet available.  Intellectual property, NDA, Phillips patents... something along those lines.  It's only 21 bit although seems to run more reliably and doesn't rely on a 500uS delay between frames to latch data that helps even more with frame rate.  Also, each LPD8806 controls 2 full RGB LEDs.

I still can't decide which to use for my project... and I know nothing first-hand about the A6281.
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That's the one drawback I have with the WS2801, while they *can* drive multiple LEDs, it would require additional components other than the normal set of resistors.  You're right on the 2MHz (without the resistor) though ... that bit me in the beginning ... eventually I said screw it, I don't need to be sending data down that fast.  I mean really ... smiley  I do like the 24bit capability of it though.

However, having said that, I have never used/tried/tested/fondled/or otherwise played with an A6281, so I can't really compare one over the other.  Does it only come in a QFN package (which would limit my usage for it as I can't solder that)?  And if it does come in a different package (TSOP/PDIP), do you know if one can get a sample batch (2 or 3)?
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It only comes in QFN, but I have a range of "demo boards" for it, heh....

http://macetech.com/store/index.php?main_page=product_info&cPath=1&products_id=10
http://macetech.com/store/index.php?main_page=product_info&cPath=1&products_id=5
http://macetech.com/store/index.php?main_page=product_info&cPath=1&products_id=35
http://macetech.com/store/index.php?main_page=product_info&cPath=1&products_id=9
http://macetech.com/store/index.php?main_page=product_info&cPath=1&products_id=1
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Unique RGB LED Modules and Arduino shields: http://www.macetech.com/store

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Cool, can you send me one?  *grin*
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Quote
The strips you linked to on kutop.com have no controller ICs and aren't RGB 5050 LEDs - hence their very low price.  Apples and oranges.

Actually they are 5050 LEDs, and there is an rgb option. Both the details say that it is a 5050 LED and the pictures of the RGB version look suspiciously like 5050s. Also I know they don't have the ICs onboard, Im not that interested in those strips actually because I prefer less pixels with more power to a bunch of pixels with low power. I was planning on cutting the strip up into 6 LED segments and then driving each one of those segments with either the a6281 or something else. I found another allegro chip the a6282 which has 16 channels and I could pair it with 2 high side drivers or two of these little babies:

http://www.mouser.com/Search/Refine.aspx?Keyword=110657578

and bit bang the PWM with either that 16 channel chip or just two shift registers with the shift register PWM library. If I used that awesome ISOFACE 8-Channel Isolated High-Side Driver I could drive some insanely powerful LEDs with just a few more components or some longer segments of that strip.

Can the LPD8806 handle 12v? I just love using this strip, its so insanely easy to use because you don't have to worry about wiring up the resistors or a connection failing or heat sinking or anything
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