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Gauging Interest in My Pi Hats

Started by vicwhit, February 25, 2022, 03:31:43 PM

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vicwhit

I have designed a full size hat for a Pi providing two pixel port outputs, plus 8 relay port controls. The relay port outputs could be used to drive solid state relays for dumb LED strings, or something similar. This hat will fit the later Pi's, including Zeros.
The second hat is smaller, in the Zero footprint size. It only provides two pixel port outputs.
Both boards incorporate readily available level shifter modules (Amazon), and 2 Mini ATO fuses (holders from DigiKey).
The boards get power from the Pi to drive the level shifters. The data signal output runs at 5V. A separate terminal block connection allows power input to drive the pixel port. Terminal block connections are provided for each pixel port, and the relay connections.
I am unsure how this project will go but I don't seek to get rich, nor lose any money on it. My idea would be to provide bare boards, to be completed by the end user.

P.S. Please disregard the connector shown on the Rpi Pixel+ Hat image. It should be on the back side. The jumpers are not needed...it was just a simple way of providing a pad connections that can be cut.

Bwinter

I've always been a big fan of the PiHat for running shows, given how economically they can be used and suitable they are for various locations in a layout (presuming of course, that the PiZeroW come back in stock this year).  I now use them exclusively in my show (and have developed several variations that I made available on tindie.com)

However looking at your uHat, I think you might be missing a resistor between the level-shifter and each of the data-port-out.

vicwhit

Back to the drawing board for version 2.
I was testing the Zero version board and found the signal out of the level shifter was not producing a 5V level to the Pixel ports. As it turns out, these level shifters do not have a rise time fast enough to support the WS2811 data stream. The sillyscope trace shows the input signal (top) and the output (bottom ) with the output level reaching about 3.5 V.
The second trace is of a GPIO port cycling High/Low at a much slower rate. The converted signal is the 5V level we need. 
So operating slow things like relays is just fine but the data rate of WS2811 is too fast for the conversion to 5V we need.
I will replace the Amazon-sourced level shifters with an SN74AHCT125N.
The full size board for a PI will retain the 8-channel level shift module to drive relays. The 4-channel level shifter for the pixels ports will be replaced with the SN74AHCT125N as well.

lanman1

Following up to see how this is going.  I have been looking for a solution to drive a single megatree.

Poporacer

Quote from: lanman1 on May 10, 2022, 11:37:39 AMI have been looking for a solution to drive a single megatree.
Depending on your MegaTree, you can use a Pi and wire to the pins directly. Or you can get something like the Kulp K8B and have a TON of room for expansion!
If to err is human, I am more human than most people.

lanman1

Thanks but I already have a kulp controller and some differential controllers, this is for standalone and with that many LEDs, I want a real level shifter.

vicwhit

I have revised the Pi Zero W board hat and have tested it on both PMW outputs. Works great. I have also created a 3D printed case to accommodate the complete assembly.

I have also revised the PI 4 version hat that in addition to the PMW outputs, also outputs 8 GPIO pins to control Solid State Relay modules. I use these control dumb LED string lights. I have not fully tested this hat yet. The 3D printed case is an ongoing project but should be ready soon.


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