Pi Box V2

Hello everyone, and welcome back. Here's something portable and fun.

This is Pi Box, an all-in-one Raspberry Pi 4-powered Mini PC with a 5-inch IPS display. In this version, we've included an SMPS inside the housing, allowing us to power the whole thing straight from AC 240V.

This is the second version of this project; the first had a different power source and enclosure design than this latest version. Previously, we included a Battery Pack in the setup, which comprised three 3.7V Lithium Ion cells connected in series to create 12V, which was then bucked down to 5V 3A to allow the Raspberry Pi to function. The issue was the limited capacity of such batteries, which resulted in insufficient backup or run time for our device. However, because this was a desktop PC, we removed the battery pack and installed a 24V 10A SMPS circuit inside, allowing us to power the device directly from AC 240V.

You can check out the Version 1 article to dive deep into the whole Pi Box topic. https://www.hackster.io/Arnov_Sharma_makes/pi-box-c5d8fd

This entire article is about the project's thorough build process, so let's get started.

Materials Required

These are the components used in this project:

• Custom PCB (Provided by HQ NextPCB)
• Raspberry Pi 4 Model 4GB
• DFROBOT 5" IPS Display for Raspberry Pi
• IP6505 IC
• 22uH SMD Inductor
• 10uF Capacitor 1206 Package
• 22uF Capacitor 1206 Package
• M7 Diode SMC Package
• LED 0603 Package
• 1K Resistor 0603 Package
• 24V 10A SMPS Circuit
• M3 HEX PCB standoffs
• M2 Screws
• 3D Printed parts in dual colors (white and orange)

DESIGN

The Raspberry Pi and the 5-inch display enclosure were kept the same for this project's design; we simply removed the battery pack circuit and the back lid from the model before adding the 3D model of the SMPS.

We wanted to reuse the existing enclosure, so we designed a second body that connects the enclosure from the bottom using two M3 nuts and bolts. This new case keeps the SMPS circuit in location. We added the SMPS AC socket to the model on the right side, where we opened the I/O ports.

Furthermore, we've also used the existing slightly tilted stand, which will be mounted on the bottom side of the SMPS enclosure with four M2 screws.

On the back side, we've incorporated a Lid part that unites or links both enclosures to form a single body. We've put mounting holes all over the Lid parameters, where we'll use M2 screws to connect the lid and enclosure.

From the front, we modeled another component that will be put on the second enclosure to improve the model's aesthetic.

After finalizing the model, we exported the mesh files and 3D printed them on an Ender 3 using a 0.4mm nozzle and 0.2mm layer height.

POWER CIRCUIT

To power the Raspberry Pi and display arrangement from the battery pack circuit we are using, which is an 11.1V 3S Lithium cell battery pack setup, we needed a Buck converter board that would step down the 11.1V to a stable 5V to run the Raspberry Pi and display.

To address this issue, we selected a Buck Converter setup that includes the IP6505 IC, a step-down converter with an integrated synchronous switch capable of handling an output of up to 10 A for fast charging protocols.

The IP6505 features an integrated power MOSFET with an output voltage range of 3V to 12V and an input voltage range of 10.5V to 28V. It can provide up to 24 W of output power by automatically adjusting the voltage and current in line with the recognized quick charge protocol, more than enough for our Raspberry Pi 4 and display setup.

The schematic was initially created and customized following the datasheet's example layout.

http://www.injoinic.com/wwwroot/uploads/files/20200220/f11cf889f6261e26dcaf52164367c836.pdf

All of the components on this board are surface mount, which reduces the need for manual soldering.

HQ NextPCB Service

After completing the PCB design, we export the Gerber data and send it to HQ NextPCB for samples.

Gerber Data was sent to HQ NextPCB, and a Green Solder Mask PCB with White Screen was ordered.

After placing the order, the PCBs were received within a week, and the PCB quality was pretty great.

In addition, I have to bring in HQDFM to you, which helped me a lot through many projects. Huaqiu’s in-house engineers developed the free Design for Manufacturing software, HQDFM, revolutionizing how PCB designers visualize and verify their designs.

HQDFM: Free Online Gerber Viewer and DFM Analysis Tool

Also, NextPCB has its own Gerber Viewer and DFM analysis software.

Your designs are improved by their HQDFM software (DFM) services. Since I find it annoying to have to wait around for DFM reports from manufacturers, HQDFM Is the most efficient method for performing a pre-event self-check.

Here is what the online Gerber Viewer shows me could not be clearer.

However, for full function, like DFM analysis for PCBA, you need to download the software. The online version only provides a simple PCB DFM report.

With comprehensive Design for Manufacture (DFM) analysis features, HQDFM Is a free, sophisticated online PCB Gerber file viewer.

It provides insights into advanced manufacturing by utilizing over 15 years of industry expertise. You guys can check out HQ NextPCB if you want great PCB service at an affordable rate.

PCB Assembly

• The PCB Assembly Process for this project begins with applying solder paste to each component pad with a solder paste dispensing needle. We're using 63/37 Sn-Pb solder paste.
• Next, we select all of the SMD components and place them in the correct spot.
• We next place the board on our Mini Reflow Hotplate, which heats the PCB from below up to the solder paste melting temperature of roughly 200 °C. Solder paste melts permanently and connects all SMD components to their pads.

SMPS

For this project, we are using a 24V 10A SMPS circuit recovered from an old 24V water purifier adaptor. This specific variation is a high-efficiency power supply that converts AC into regulated DC with low energy loss.

The operation of an SMPS involves several key stages. First, the rectification and filtering stage converts AC voltage into pulsating DC using a rectifier, which is then smoothed out by a filter capacitor. The next step is the switching mechanism, where a MOSFET or other semiconductor switch rapidly turns on and off, enabling precise control over voltage conversion. A high-frequency transformer is typically present to step up or step down the voltage, making the circuit more efficient and compact. The control circuitry, often managed by an integrated circuit (IC), continuously adjusts the switching frequency to stabilize the output voltage and maintain efficiency.

This 24V 10A SMPS circuit is capable of delivering up to 240W of power, which makes it suitable for applications requiring a stable and powerful DC source.

SMPS and Power Circuit

• To begin, connect the SMPS output terminals to the Power Circuit's Vin and GND terminals with wires.
• Then, connect a multimeter probe to the Power Circuit's Vout and GND.
• When we fed 240V AC into the SMPS, we got a steady 5V, which we will utilize to run our Pi indefinitely.

SMPS Enclosure Assembly—Adding the Accent part

The accent part, which we 3D printed in two color themes, is attached to the front side of the SMPS enclosure. We apply super glue to the front side before placing the accent part in position.

Pi Box Body and SMPS Enclosure Assembly

• Next, we begin the Pi Box and SMPS Box assembly procedure by connecting the two enclosures and aligning the mounting holes.
• we then use two M3 nuts and bolts to fasten these two together.

Final Assembly

• The SMPS circuit is now installed over the four screw bosses, and we use four M2 screws to secure it in place.
• We then insert the Power circuit into the Pi Box shell, securing it with an M2.5 bolt over one of the 5-inch display's screw bosses.
• The Power Module's 5V and GND JST connector is then inserted into the 5V and GND.
• Next, we attached the lid to the back side of the Pi Box. Combine the enclosure and secure it in place with six M2 screws.
• Finally, from the bottom side of the design, we attached the previously 3D printed Holder from version 1 and secured it in place with four m2 screws, completing the assembly process.

RESULTS

The End Result of this tiny project was version 2 of the Pi Box, which now includes an SMPS, allowing us to power this system with AC 240V. The batteries have been totally removed, and we can now utilize this small device as a Pi computer.

For testing, we used Recalbox OS and ran Quake 1 and 2 on our Pi 4, which ran nicely. This project isn't about how the Pi 4 works or how well it performs; it's about how this setup is powered entirely by an AC wall socket and requires no additional adapter or battery to operate.

If we want to increase its power, we can replace the Pi 4 with the new Pi 5 with an NVME hat, which will provide enough power, but that is a topic for a different article.

Special thanks to HQ NextPCB for providing components that I've used in this project; check them out for getting all sorts of PCB- or PCBA-related services for less cost.

Thanks for reaching this far, and I will be back with a new project soon.