WS2801 IC confusion

Other Hardware LEDs and Multiplexing
1

I am working on a PCB which uses 1616 RGB LEDs ( http://www.mouser.com/ds/2/216/APTF1616SEEZGQBDC-80960.pdf ) controlled with a WS2801 IC ( http://www.adafruit.com/datasheets/WS2801.pdf ) for each LED.

I am pretty new to wiring LEDs, so I figured I would try to simulate the wiring in RGB strip lights.

The WS2801 datasheet has very useful common application wiring diagrams, however what I want to do is a little tricky...

Here are my two questions:

Can I wire two LEDs per IC? And if so, what would that wiring look like? I want to have pairs of 2 LEDs that will be the same color in my strip.

Also, how many ohms should the resistors be? And should they be in line before the WS2801 or after?

Sorry for the noobish questions!

2

rootklm:
I am working on a PCB which uses 1616 RGB LEDs ( http://www.mouser.com/ds/2/216/APTF1616SEEZGQBDC-80960.pdf ) controlled with a WS2801 IC ( http://www.adafruit.com/datasheets/WS2801.pdf ) for each LED.

I am pretty new to wiring LEDs, so I figured I would try to simulate the wiring in RGB strip lights.

The WS2801 datasheet has very useful common application wiring diagrams, however what I want to do is a little tricky...

Here are my two questions:

Can I wire two LEDs per IC? And if so, what would that wiring look like? I want to have pairs of 2 LEDs that will be the same color in my strip.

Also, how many ohms should the resistors be? And should they be in line before the WS2801 or after?

Sorry for the noobish questions!

Hi rootklm

Im a kind of a noob too :stuck_out_tongue: but i already learn some stuff about those IC.

First: the ws2801 can only drive 3 channels so a single rgb led. For two led you will need a LPD8806.

Second: the resistor depends on several factors like the supply voltage, voltage drop across the LED and the desired LED current, etc. You can find a led resistor calculator here http://ledcalc.com/. I think that the resistor can go before or after the IC,if it was a capacitor there will be some differences.

:slight_smile:

3

Well, the LPD8806 does look like a very capable chip, however I can't find a lot of useful documentation on it, and some folks are saying that it is hard to get a hold of the IC by itself.

That is alright though, since I don't really need to control the pairs individually (they can remain the same color).

Would it work if I used a 220 ohm resistor on each LED and the sets of two LEDs connected to the WS2801 via the R G and B terminals?

4

I think that may be possible do connect more than one led to the IC.
Check this out: Appnote: Using mosfets to expand the WS2801 LED Driver | The Longhorn Engineer.

For the resistor i can`t tell if yes or no. It depends on the variables that i tell you before.

:slight_smile: