I purchased the Adafruit Perma-Proto Pi HAT board for my RPi. I want to transition my prototype that I built on a breadboard, onto the Perma-Proto HAT. One of the things I currently have connected to my breadboard is a length of NeoPixel LEDs that I connected via the following tutorial:
On my breadboard, just like the tutorial, I have the Logic Level Converter extending across the gap in the centre of the breadboard, and I have my 5V power supply connected to one side of the board.
When I read the writing on the top of the Perma-Proto HAT, one rail suggests it’s “+3V”, and on the opposite side, it indicates “+5V”. So does that mean these rails are already powered as indicated, and I therefore don’t need the power and ground jumper cables going back to the GPIO pins?
Sorry for the delay in getting back to you on this one! We have gone and grabbed one of the Perma-Proto Pi HATs off the shelf and tested with our multimeter to confirm this for you.
Referring to the image below, all the 5V, 3V and Gnd connections from the GPIO of the Pi (top two rows) are connected by internal traces inside the HAT. So once your HAT is installed on the Pi, you will have 3V, 5V and Gnd supplied where labelled on the HAT. No need to use you logic level converter that you currently have on your breadboard.
Referring to the below image, all the other pin locations are connected via visible traces as per the image. Similar to a standard breadboard that has rows and columns connected for convenience.
Really appreciate your further investigation @Matt. Thanks for posting your findings.
Please help me then: from the NeoPixel tutorial I was led to believe that you really should use an external power supply for the LEDs and to not use the RPi’s 5V supply. I have it that way (as per the tutorial) currently on my breadboard.
Is that not correct then, and am I safely able to power the LEDs directly from the 5V side of the Perma-Proto HAT?
Secondly, if I were still to use the external power, I’m guessing I can’t simply add it to the “+5V” and associated “GND” side of the HAT can I?
I see, apologies - I did not read your question closely enough, and may have been a tad misleading as a result!
The answer is essentially this: Yes, your Pi and the NeoPixels need separate power supplies. The NeoPixels need an external source of power because of their current draw, and the Pi needs it’s own power supply (such as a standard Pi PSU) because it cannot be supplied power via the GPIO pins (AFAIK - don’t quote me but that’s not a good way to feed power into the system).
Additionally, yes you are right, we cannot mix these power sources. The grounds must be common (connected together) but we cannot connect 5V terminal from the external power supply to the 5V GPIO on the Hat connected to the Pi. That is a key point for later where I explain the ‘tricky bit’.
So looking at our circuit diagram above - you are simply transferring everything you’ve made on your breadboard onto your HAT. The HAT is simply a solderable breadboard with a slightly different layout It has columns and rows connected similar to a breadboard and these can be seen by flipping it over to see which pins are connected by a visible trace. The GPIO section of the HAT, connected to the Pi GPIO, breaks out the 3V and 5V pins from the Pi to some easy to access pins as labelled on the HAT.
Here’s the tricky bit - Do not connect the 5V external power supply to the 5V on the HAT! This is like wiring your external 5V supply directly to the Pi Power supply and we don’t want that. Grounds need to be common, but the 5V positive terminal can’t be. The HAT tried to make things easier for us by breaking out that 5V from the GPIO but in this particular case it has only added extra complication!
If this is still hard to follow - don’t stress. I’m working on a wiring diagram for you now and I’ll upload it when I’m done so you can just copy it off that
Once again @Matt, I really appreciate your effort in explaining this. Yes, I look forward to the updated wiring diagram. I do understand what you’ve written, but just unclear at this stage what to then do with the 5V positive terminal. I’m sure your diagram will unveil all.
Thought we had Fritzing available on this computer but we had to use Paint in the end!
So note: The HAT sits onto the Pi GPIO pins but the image has them upside down with respect to each other. So note the arrows showing where the pins pop up on the HAT when it is installed on the Pi the correct way
Also yes the wiring for the LED’s could be simpler but hindsight is 20/20! Just kept going with whatever I had already drawn.
So yeah, note the 5V rail is avoided because it is already connected to the Pi 5V from the GPIO pins and we don’t want to connect our 5V external supply to it