I have a bunch of these guys. Can’t I use this for bumping up a signal for a Teensy from 3.3v to 5v for WS2812 chips? I have 3 separate WS2812 sets of lights I need to drive separately. I would think I could hook up the 3.3v/GND and then two signal pins to this from a teensy LC then 5v/GND and pins to the strips. Then I can just use the 5v (pin 17) for the output of the third strip. This make sense or am I off base?
The WS2812 should be happy with 3.3v, unless you have the really old picky chips. WS2812b, KS68??, etc need 5v supply but in my experience are fine with 3.3v data.
@Gordon_McLellan WS2812B’s are sometimes fine with 3.3v data - and that’s what ends up tripping so many people up. If your power supply is pushing out 5.3 or 5.4V instead of 5v, you’ll quickly find the WS2812B’s having a problem reading 3.3v signals 
@Justin_Eastman I am skeptical of these - i’ve used other level converters that are marked as being for I2C - which is slower than the WS2812B data rate (I know, hard to believe, something that’s actually slower than those fuckers? And yet, here we are - and they haven’t been able to keep up with the data rate. (Hmm, now that I have an actual scope, I should look at what the output of those chips looks like). Which is how I usually end up back at the 74HCT245.
Yeah I have experienced the WS2811/12/12B chips working fine with 3.3v. I just don’t use Teensy all that much and figured if that would do the trick why not just use it.
Thanks for the input.
It’d probably be better to skip the level converters than use one that can’t keep up. if you’re going to drive the WS28xx directly from the teensy 3.3v outputs without a shifter, make sure the voltage into your leds is below 5.2v (measure the output of your power supply with no load)
Thanks for the tip. What is the behavior when the voltage is higher? You get flicker? Lose LEDs?
@Justin_Eastman I have no experience with that directly, there’s lots of warning on the internet about 5v io burning out the first pixel.
It’s not a matter of damaging the pixels - I’ve accidentally pushed 7v into them and had them work.
It’s more a problem that when the pixel is getting 5.4V into it, it no longer reliably detects a 3.3v signal as high - this causes all sorts of fun data corruption as you’re writing out led data - which could cause flashing, strobing, random colors, or just darkness.
@Daniel_Garcia 7v on the IO line? Why is there so many references to blowing out the first pixel, just Internet echo-chamber effect?
found these
http://www.dx.com/p/geeetech-logic-level-converter-for-i2c-spi-normal-serial-red-377856#.VsZKDubOSlc
they use the BSS138. the rise times seem pretty fast… how do I tell if it is fast enough?
Here is the adafruit datasheet on the BSS138:
The WS2811 chips did not have polarity protection. I suspect that is a big problem. The 4 pin WS2812B have that protection in them… perhaps that is why? I personally have never blown a WS2811/12/12B, only WS2801s.
@Justin_Eastman since the IO is unidirectional, check out this simple solution http://www.hobbytronics.co.uk/mosfet-voltage-level-converter
Humble 2n7000 has on/off time MAX of 10ns, so that’s many many megahertz, certainly fast enough for serial io
@Gordon_McLellan no - 7v on the VIN line.
http://happyinmotion.com/?p=1247 has some discussion on level shifters that are out there and what the WS281x play well with.
I have never been able to get any of these level shifters to work properly! as @Daniel_Garcia WS2812b pixels will work fine with a 3.3v signal but not always. or pretty much any project i do that involves 3.3v logic I build one of these http://www.elec-tron.org/?p=1184 and i put it as close to the MC as possible
I see more stuff on there than would really be needed for two FET level translators. However, those are for fairly slow signals due to gate capacitance. For single-direction translation it’s just as easy to use a BJT level translator which should be faster.
I tried out a few level shifters such as http://www.watterott.com/en/Level-Shifter but non of them worked besides the 74HCT245.
Problems with WS2812 occur especially when the data line to the µC is too long.
However, they have an internal signal reshaping circuit. That means if you use one ‘oblation-LED’ close to your µC you got your level shifter almost for free
Since the Teensy will handle 3.3-9Vin, why not feed it 5v and then power the LEDs off the power supply and not through the Teensy’s power out?
Not talking about powering the WS2812s but rather the data line is rated to be a 5v input. The teensy has mostly 3.3v pin voltages
I haven’t played with the Teensy yet but I just got one in. So there may be issues driving LEDs with the Teensy? Is this specific to ws2801, ws2812s, lpd8806s?