Automation Phat and a neopixel RGB LED


#1

It would really help my project to send data to a single rgb led ws2812b from one of the outputs of the automation phat. I note they are connected to the -ve side of the circuit which is fine for my bell actuator , protected by diode , but the i can’t quite work out how to connect the signal wire of the neopixel led. as it requires PWM would i be able to use the MOSI pin of the SPI? or does that operate at the 3.1v level.? appreciate i could use a multimeter to test the signal level , but disability makes that a bit tricky , any advice would be welcome


#2

RGB LED might be easier to setup and code? https://shop.pimoroni.com/products/led-rgb-clear-common-cathode?variant=44298388106
In any case have a look at this, https://learn.adafruit.com/neopixels-on-raspberry-pi might help?


#3

Thank you for your reply I started at the adafruit article last weekend. i was trying the automation hat to reduce the effect of my shonky soldering .on circuit performance , i think i’m probably using mallet to push a pin in using an automation phat. Oh well time to blow up a 3rd SN74AHC125 ;) I think you are right inevitably i will be drawn ot using an rgb led its just 3 pins for a single led irks me


#4

It’s not 1 LED is the thing. It’s 3 LED’s in the one housing. There just isn’t a control chip inside. It’s a lot easier to light them up is all. If they didn’t have a common anode or common cathode there would be 6 pins. ;)


#5

i meant as opposed to the one pin per chain of ws2812bs. I’m moving the project over from arduino the original project ran 3 strings of ws2812bs on 3 pins. With my tremor, 3 pins per RGB output unit is 3 times the chances of my soldering being the point of failure.


#6

Ah, OK I’m on the same page now. =) I’ll wish some good luck and good Carma. ;)


#7

cheers! I think Im probably going to try again with the line driver chip.


#8

TBH, Automation pHAT isn’t really a good fit for driving NeoPixel strips. You’d be as well just driving them direct from the Pi’s GPIO.


#9

Yes i’ve reverted to using 2 channels of an SN74AHCT125N. one to drive a 2222 transistor for the bell actuator with a diode for back emf protection and driving the data line on the neopixel from the other… i was hoping to avoid some construction , but realised the adaptations of the automation phat were getting unwieldy and just providing further potential points of failure.