I'm trying to drive WS2812B LEDs with the GPIO pins of the ESP32. Works OK if I cheat and turn the voltage down to 4v so the differential is closer, but that's a hack. I used a level converter on my last project but couldn't get it to work this time around.
Then I realized, there's not a lot of current load, but someone here mentioned that the level converters aren't designed to handle any load at all. So what about a transistor or mosfet?
If I have a 3v3 and 5v pins (which I do) I should be able to use the 3v3 GPIO pin to trigger a 5V feed through the transistor, right?
If so, can someone tell me in small baby talk words which pins go where and which type of transistor or MOSFET I should use? I'm driving the data for about 700 LEDs.
[u]Here is a transistor driver[/u]. Almost any NPN transistor should work since it's low current, and you can leave out the diode since it's a non-inductive load.
(MOSFETs usually like higher gate voltage so in this case a regular transistor is probably better.)
I'm driving the data for about 700 LEDs.
They are usually controlled-addressed serially and they are buffered so the control current & voltage only goes to the first one.
But, 700 is a lot and you'll get a voltage drop in the power if you try to power them all in a single string. (The LEDs will be dim at the far end.)
No, not powering it via my circuit at all. It has a shared reference ground but is powered by an external supply. Thanks for the transistor info! I'd done it once before to control an old RGB strip, but I just picked three random NPN and it worked, so wanted to be a little more rigorous!
The problem with just any old transistor is that they will not always go as fast as you need. Note that the link to the schematic provided will invert the signal, which is no problem if the libiary you use allows for an inverted data signal, otherwise it will not work, or you need two one after the other.
Despite the advice of some of the best experts on the forum, I failed to make a working level convertor using transistors, using either MOSFETs or BJTs for my Wemos mini and string of ws2811 LEDs. Ok, my choice of MOSFET was not suitable (2N7000) but the NPN (BC337) didn't work either for unknown reasons.
I had been using one of those 4-channel logic level convertor modules you can buy on eBay etc for I2C busses. It worked ok, but became eratic if I touched any component leg with a finger.
The expert's suggestion that works really well for me is 74HC14. This is a hex invertor chip, so connect two gates in series and power the chip with 5V. Because of its Schmitt Trigger inputs, it happily responds to 3.3V logic input signal. LEDs now work perfectly with no eratic behaviour when touched.