Portable Multi-OS Audio Long-working Pi Deck

I designed this handheld deck being inspired by other HandHeld projects. I also wrote the step-by-step guide to make it straightforward for anyone to build. This project is completely free to build under the Creative Commons BY-NC-SA 4.0 license. During working on articles I found my version visually is similar to "YARH.IO MKI" https://yarh.io/yarh-io-mki.html, but it was designed from scratch.

I started by assembling of acrylic case with fan to Pi3B+ using screws 2.5mm x 25mm. Fan' existence is important as it will cool down Pi.

Then I soldered wires to probe points at back of board Pi3B+ named PP2 for further ( not now ) connection to 5V positive power supply and (PP5 or PP6) for 5V negative power supply, about 10 cm long.

Then I prepared SD card extender 25 cm long. Initially SD card extender does not work, and I found that it is common problem and is solved by desoldering one resistor of 330 Om.

https://forums.raspberrypi.com/viewtopic.php?t=269457

https://forum.arduino.cc/t/micro-sd-extender-cable-not-working/958431/7

Then I connected SD extender to Pi and folded cable so that only SD case was out of Pi.

Then I screwed the screen to the Pi case using same 2.5mm x 25mm screws and connected the DSI cable to the display.

I prepared three USB extenders: firstly I soldered the male and female USB connectors using 0.5mm wires, and then filled them with epoxy resin. Length is 4 cm.

To power Pi/Keyboard/Li-ionindicator I used IRFZ44N MosFET, although Gate threshold voltage is 2V-4V at the datasheet, practically at 1.5V the Drain current is 10-20mA, and all electronics work fine even at 3.0 volts at Gate, but practically Battery voltage won't decrease lower than 3.3V.

At the diagram, I represented how I connected each electronic component.

I inserted a wireless Keyboard USB stick to one of four USB ports to establish communication between Pi and Keyboard.

For keyboard, I disconnected an internal battery, and left MosFET inside of Keyboard.

All MosFETs and soldered joints were covered by hot glue to prevent short-circuit.

For other Raspberry Pi versions 4/5, the Gate voltage should be supplied from some Buck converter at least 5v, because Pi 4/5 current consumption is bigger.

Then I made holes in the bottom part of the Box for the PowerBank module, USB extenders and SD card extender.

Next step is putting the powerbank module and USB extenders in appropriate holes and connecting battery ( 10Ah for now) to powerbank module.

Keyboard was fixated above Battery by placing on polystyrene foam and pins for screws, and fixated by hot glue.

Pi fixated by polystyrene foam

I cutted out of top box part:

- height from ~30 mm to 14-15 mm.

- all plastic parts that interfere Keyboard and Touchscreen interaction.

- pins for screws

I fixated Li-ion indicator by polystyrene foam and hot glue. Button is just inserted, fixated by it's own friction.

I fixated the bottom and top box parts with reinforced adhesive tape.

I added two SD adapters for now, but the amount of SDs is limited only by Box's free space.

I fixated by reinforced adhesive tape.

I added several 10Ah/(2x2Ah) Lipo batteries under the Keyboard to increase Battery capacity up to 24 Ah.

Soldered joints are isolated by hot glue.

My Pi 3B+ with Screen without Keyboard with OSs (Batocera, Raspberry Pi OS, Armbian) consumes roughly ~1.25A ~5V.

(24*3.7)/(1.25*5)=14 hour optimistic maximum, but if I took 2/3 of 14 hours =~ 9.5 hours Pi should work fine.

Keyboard enters the low power mode after 1-2 minutes, so it's consuming is not counted.

PiUniDeck can be used as PowerBank due to PowerBank module usage.

Now you can enjoy your new deck for work and fun.

I decided to add a keyboard backlight after couple of nights of testing.

I cutted four 3528 SMD LEDs from LED strip and soldered them in parallel to indicator +/- and hot glued to the side of the keyboard hole.

For adding sound I used audio Jack 3.5mm, mini 8 Om speaker, mini audio amplifier, wheel-like variable resistor 1kOm.

Left and Right input audio pins of Jack3.5 are connected by soldering together without resistors and connected to Left input pin of the amplifier.

Resistors are adviced to use at forums, but no significant audio noise or other issue without resistors.

Powering for the amplifier is connected in parallel to 5V Pi power supply.

Jack3.5 is inserted to Pi Jack3.5 socket.

Amplifier is fixated by hot glue behind cover with SD cards.

Speakers are fixated by hot behind the Li-ion accumulators side cover and directed to the user.