Custom Raspberry Pi "hat" for interfacing with a wide range of logic voltages

[Benjamin Smith]

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Hey Microscopists,

*The short:*
I recently developed a simple, easy to build PCB "Pi hat" that allows a
Raspberry Pi to directly interface with a wide range of logic voltages,
while still allowing for the use of a CPU heatsink and fan.

Here is a link to the manual with images of the device:
http://bit.ly/2GYawoD
Here is a link to the full Github repository with CAD files, KiCAD files,
bill of materials, Gerber files, etc.:
https://github.com/Llamero/RPi_IO_Hat_v1

*The long:*
We recently needed to directly interface the GPIO pins on the Raspberry Pi
to several different logic voltages (28V, 5V and 3.3V), and surprisingly I
could not find a "Pi Hat" that could do this.  Additionally, the Pi hats
that do exist block the ability to effectively cool the CPU/GPU, which is
important when playing full screen resolution videos as part of an
experiment, and/or running the CPU at 100%.

Therefore, I designed a simple TTL Pi hat that fulfills the following
requirements:
1) Allows the GPIO pins to interface with a wide range of logic voltages
(±40V input, 0-100V output at up to 1W each).
2) Allows for direct pin interfacing to eliminate latency and to catch
simultaneous trigger events.
3) Leaves room for a CPU heatsink and fan and provides a power source for
the fan
4) Will fit in a standard Raspberry Pi enclosure
5) Protects the GPIO pins from over-current and over-voltage.
6) Uses a stackable header to allow for additional connection to a
breadboard.

While rudimentary in design, I realized that this still could be a
universally helpful device, so I figured I would share it with the listserv
so you guys don't wind up having to put forth redundant efforts.

If anyone has any questions, please feel free to ask.

Cheers,
  Ben Smith

--
Benjamin E. Smith, Ph. D.
Imaging Specialist, Vision Science
University of California, Berkeley
195 Life Sciences Addition
Berkeley, CA  94720-3200
Tel  [phone]
Fax [phone]
e-mail: [hidden email]
http://vision.berkeley.edu/?page_id=5635 <http://vision.berkeley.edu/>

[Tim Feinstein]

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*****

Hi Ben,

I love that you did that! Do you think it could be used to make a field stimulator for cardiomyocytes?  I have been trying to do that with an Arduino, but I've had a problem making a circuit that gives me a steady, adjustable voltage over 5V without PWM.  

All the best,


T

Timothy Feinstein, Ph.D.
Research Scientist
Department of Developmental Biology
University of Pittsburgh

 


On 2/23/19, 12:45 AM, "Confocal Microscopy List on behalf of Benjamin Smith" <[hidden email] on behalf of [hidden email]> wrote:

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    Post images on https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.imgur.com&amp;data=02%7C01%7Ctnf8%40PITT.EDU%7Cc520b5118caf462d967308d699522169%7C9ef9f489e0a04eeb87cc3a526112fd0d%7C1%7C0%7C636864975382417795&amp;sdata=MVgqZ8jQbOi5gjcD6BywvRO3uqtMWdTjIUhu7O5Bt8A%3D&amp;reserved=0 and include the link in your posting.
    *****
   
    Hey Microscopists,
   
    *The short:*
    I recently developed a simple, easy to build PCB "Pi hat" that allows a
    Raspberry Pi to directly interface with a wide range of logic voltages,
    while still allowing for the use of a CPU heatsink and fan.
   
    Here is a link to the manual with images of the device:
    https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fbit.ly%2F2GYawoD&amp;data=02%7C01%7Ctnf8%40PITT.EDU%7Cc520b5118caf462d967308d699522169%7C9ef9f489e0a04eeb87cc3a526112fd0d%7C1%7C0%7C636864975382417795&amp;sdata=yW8x4qANyOzGGd62qjy0ugpNyvVUtT0c2bUxxGfns1k%3D&amp;reserved=0
    Here is a link to the full Github repository with CAD files, KiCAD files,
    bill of materials, Gerber files, etc.:
    https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FLlamero%2FRPi_IO_Hat_v1&amp;data=02%7C01%7Ctnf8%40PITT.EDU%7Cc520b5118caf462d967308d699522169%7C9ef9f489e0a04eeb87cc3a526112fd0d%7C1%7C0%7C636864975382417795&amp;sdata=bUGJmqFlkwFiz7NSuanZMVNlrJ4Da8nflQ5kYO7nfWY%3D&amp;reserved=0
   
    *The long:*
    We recently needed to directly interface the GPIO pins on the Raspberry Pi
    to several different logic voltages (28V, 5V and 3.3V), and surprisingly I
    could not find a "Pi Hat" that could do this.  Additionally, the Pi hats
    that do exist block the ability to effectively cool the CPU/GPU, which is
    important when playing full screen resolution videos as part of an
    experiment, and/or running the CPU at 100%.
   
    Therefore, I designed a simple TTL Pi hat that fulfills the following
    requirements:
    1) Allows the GPIO pins to interface with a wide range of logic voltages
    (±40V input, 0-100V output at up to 1W each).
    2) Allows for direct pin interfacing to eliminate latency and to catch
    simultaneous trigger events.
    3) Leaves room for a CPU heatsink and fan and provides a power source for
    the fan
    4) Will fit in a standard Raspberry Pi enclosure
    5) Protects the GPIO pins from over-current and over-voltage.
    6) Uses a stackable header to allow for additional connection to a
    breadboard.
   
    While rudimentary in design, I realized that this still could be a
    universally helpful device, so I figured I would share it with the listserv
    so you guys don't wind up having to put forth redundant efforts.
   
    If anyone has any questions, please feel free to ask.
   
    Cheers,
      Ben Smith
   
    --
    Benjamin E. Smith, Ph. D.
    Imaging Specialist, Vision Science
    University of California, Berkeley
    195 Life Sciences Addition
    Berkeley, CA  94720-3200
    Tel  [phone]
    Fax [phone]
    e-mail: [hidden email]
    https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fvision.berkeley.edu%2F%3Fpage_id%3D5635&amp;data=02%7C01%7Ctnf8%40PITT.EDU%7Cc520b5118caf462d967308d699522169%7C9ef9f489e0a04eeb87cc3a526112fd0d%7C1%7C0%7C636864975382427808&amp;sdata=ug0ai822bs6pojuOOgBV7bF98OGdjicj3Nk5mXd2DbA%3D&amp;reserved=0 <https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fvision.berkeley.edu%2F&amp;data=02%7C01%7Ctnf8%40PITT.EDU%7Cc520b5118caf462d967308d699522169%7C9ef9f489e0a04eeb87cc3a526112fd0d%7C1%7C0%7C636864975382427808&amp;sdata=rvMcztKmSacjTWzi86uphtlUaRJB15G8rDooOf4QO1c%3D&amp;reserved=0>