EEZ H24005: Open Source Bench Power Supply

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Details

A fully open source programmable power supply offering professional lab-quality features and performance

As Featured In

Hackaday

Hackaday

"until you check out [Denis]’s bench power supply build, you may not even know what you’re missing."

Ham Radio 360

"...explore how to connect micro controllers and single board computers to circuits and sensors to interface with the real world."

electronics-lab

"In addition to modularity, programmability, openness, and DIY, reliability was one of the key features and design guidelines of the designing process."

Open Electronics

"The EEZ H24005 is fully free and open source."

We’ve stopped taking new orders for the EEZ H24005. Please subscribe to the project updates to be notified if/when a next batch becomes available. See this update for more information.

Introduction

Electronic test & measurement (T&M) tools have an indispensable place on the workbenches of hobbyists, students, and DIY enthusiasts. These tools are also essential for educational and R&D institutions, who rely on them in their classrooms and labs. The EEZ Open project is an attempt to bridge the gap between T&M tools for hobbyists and students and the tools relied on in commercial, professional environments. It does that by combing the best of both sides.

Typically, the tools used by DIY groups, students, and hobbyists tend to be simple and inexpensive. Driven by a need to learn and experiment, they are generally built around free and open source software (FOSS) and hardware (FOSH). As they are passed around and shared, they create a community of users around them who are willing to assist with feedback on how to improve the project and how to avoid common mistakes. These tools are often of lower quality, have limited functionality, and lack proper documentation. That is also true of the software side, where support for some T&M instruments’ programming and interconnecting standards can be almost non-existent.

By contrast, commercial T&M offerings provide reliable and feature rich “turn-key” solutions, and they come equipped with software that lets users create centralized control of and communication between different T&M devices. However, commercial solutions also have two significant drawbacks: high cost and closed design that is often protected by one or more patents. The high cost of commercial T&M instruments makes them unattainable for the DIY & educational groups. This, along with the limited functionality of DIY tools, puts a damper on experimentation and creativity. Similarly, in educational environments, the expense of commercial-grade tools limits students’ ability to get hands-on experience.

Free and Open Source

The EEZ Open project seeks to solve these problems with a unique approach to building T&M tools. One of the best parts of the project is its software, both in terms of already implemented features and because of the availability of development tools that allow users to quickly model new or modify existing functionality for their own unique needs. This campaign seeks to launch the first device made explicitly for this software: the EEZ H24005, a dual-channel, programmable power supply whose feature set exceeds many commercial offerings.

Complete documentation and the open source software is available on our GitHub repositories, one for the hardware and one for the software. The EEZ H24005 power supply is now in its fifth revision, with three public releases completed. Firmware M3 (milestone 3) was completed in December, 2016, with support for a comprehensive SCPI command set and a TFT color touch-screen display. The command set is documented in a 100+ page SCPI reference guide.

The EEZ Open software suite currently consists of two tools:

  • Firmware simulator is a “virtual instrument” for exploring and testing all functionality without needing the physical device on hand. It helped us speed up development by avoiding things like, for example, frequent and time consuming uploading to the MCU. You can download the latest stable version. Simply download and install to see what has been implemented using SCPI commands, the command line, and the GUI console/front panel.
  • EEZ Studio is a powerful WYSIWYG development tool for creating and editing the menus and pages on a local display (in this, the color TFT touch-screen on the H24005). We found it incredibly useful and time-saving when we were developing the menus and pages that display the power supply’s information and status. EEZ Studio is not quite yet publicly available, but it’s not required for EEZ H24005’s firmware in run-time. We are planning to publish the first complete version shortly after the campaign’s end for those who want to play with the menus and display info.

Both applications run on multiple OS’s (Linux, Windows, OS X, etc.) with the Arduino IDE supported as a first target platform. We chose it because it’s also open source and cross-platform and well known within the DIY and maker communities. Modifying existing code, adding code to achieve new functionality, or simply uploading to our new firmware releases shouldn’t be a problem.

Another Bench Power Supply?

The EEZ H24005 is not just another programmable bench-top power supply. While its software, hardware, and mechanical aspects are designed to compete with any commercial offering, because it is fully free and open source, it provides a level of independence and hackability that simply doesn’t exist with proprietary, traditional tools.

The EEZ H24005 can’t be easily categorized as either a typical DIY solution or standard commercial solution for two simple reasons: it’s packed with features that cannot be found in DIY projects, yet its design (software, hardware and mechanical) is free and open source that is not-existent and by default still forbidden within professional/commercial solution. No more paying for unlocking additional firmware features, no more waiting for repairs or hunting for service manuals if someone makes a mistake and lets the “magic smoke” out.

Our design keeps these key concepts at the fore:

  • Modular design – different people have different power requirements for different projects. Therefore, the EEZ H24005 consists of four modules + MCU board (Arduino Due or compatible 32-bit ARM board), so changing one part of the system does not mean everything else has to be thrown away and a new “mainboard” created.
  • Programmability – experimenters and even every-day users have diverse needs for a power supply scheme: they want to play with analog circuits or digital circuits that could include power-demanding motors, lights, etc., or they may need to charge batteries with different chemistry that demands different charging schemes. Or, perhaps a programmed voltage and current sequence is needed for testing performance of other circuits. All that can be done via SCPI commands, allowing power-users to add new features without having to wait for a commercial firmware upgrade that might never come.
  • Reliability – Powering circuits and/or charging batteries must be safe, even if left untended for prolonged periods. To ensure safety and reliability, we spent a lot of time designing our circuits and implementing multiple protection and self-test features which we then tested in real life situations.
  • DIY friendly – The miniaturization of electronic parts makes them hard for a DIY builder to work with them. We selected components in sizes and packages that are easy to hand-solder without special equipment or skills.
  • Connectivity – With USB and Ethernet connectivity, you can be a few steps or a few thousand miles away from your EEZ H24005 and still communicate with it. Communication also helps when many units are deployed in one place, like a classroom or lab.

Full teardown of the EEZ H24005

Hardware Features & Specifications

The EEZ H24005 has a feature set similar to any other commercial, bench-top power supply. But it also has features that make it uniquely different. We’ve broken it all down below:

Unique Features

Feature Description
Local user interface 3.2” TFT color touch-screen and encoder knob
Channel coupling Serial (up to 80 V), Parallel (up to 10 A) using built-in power relays (no external wiring is required)
Remote sense Doesn’t need external wiring thanks to built-in signal relays
Digital control Arduino Due (or compatible) 32-bit ARM MCU board
Power control AC In-rush current limiter
Remote/external voltage programming Surge protected, 2.5 V for full scale operation
Battery temperature monitoring Opto-isolated V/F input (for battery NTC)

The EEZ H24005 has a unique design that is highly efficient when high power output is required, but can also provide low ripple, low noise output for sensitive, low power circuits.

Its user-interface is also distinct. We believe the combination of a touch-screen display and single encoder knob provides a UI that successfully replaces the traditional “function” keys, keypads, potentiometers, encoders, switches, etc. With the EEZ Studio, the GUI displayed on the touch-screen can be easily modified to satisfy different users’ needs and tastes. We look forward to getting feedback from users as they interact with our GUI and make improvements and changes.

In addition, there are additional features that will be unlocked and included for free as the campaign reaches its various stretch goals. So far, we’ve reached the first stretch goal (encoder knob).

Standard Features

Feature Description
No. of channels 2 (isolated)
Voltage range 0 – 40 V (1 / 10 mV step)
Current range 0 – 500 mA (0.1 / 1 mA step, stretch goal 3), 0 – 5 A (1 / 10 mA step)
Max. power per channel 155 W (with selected AC/DC modules, otherwise up to 200 W)
Topology Serial hybrid (switching pre-regulator with “100% duty cycle” capability, linear post-regulator)
Built-in protection mechanisms Remote sense reverse polarity, MCU watchdog (heart-beat), Power good
Other channel’s features Output enable, Down-programmer
Cooling 60 mm fan (speed controlled with channel’s temperature sensors), passive heatsink on post-regulator’s power MOSFET
Connectivity USB, Ethernet (USB port is now fully isolated and both inputs come with ESD protection thanks to stretch goal 2)
Other peripherals Buzzer, RTC with supercap backup, EEPROM, SDcard socket
Remote/external voltage sense Yes, using built-in signal relays (no external wiring is required for internal sensing)
Digital I/O 1 x input (protected, 3.3 and 5 V level logic), outputs: 1 x opto-isolated, 1 x power relay (stretch goal 2)
Power control AC power switch (rear panel), AC soft-start/stand-by (firmware controlled), MCU DC power switch (front panel)
AC power 85-264 V / 47-63 Hz (manually selected), additional input protection (TVS, MOV, SAR)
Dimensions Metal enclosure: 293 mm (W) x 90 mm (H) x 272 mm (D)

Components

The EEZ H24005 is composed of the following parts and modules:

  • AUX PS module
  • Power board (one per channel, two in total)
  • Arduino shield
  • Metal enclosure
  • Nuts, bolts, and electromechanical parts
  • Wire harness
  • Arduino Due
  • 3.2” TFT color touch-screen display (carried by Arduino shield)
  • AC/DC power module, 48 VDC, 155 W, (one per channel, two in total)

EEZ H24005 modules: 1. Power boards, 2. AUX PS module, 3. Arduino shield

All modules can be easily mounted into a pre-drilled, customized metal enclosure as shown below. The enclosure consists of four parts, is made of 1.5 mm thick aluminum, and comes with screw-fixed rubber feet and front panel handles.

To simplify assembly, the number of cables has been minimized. Cooling is provided by 60 mm fan and two passive heatsinks that are also used to securely mount the power boards and further improve the mechanical strength of the enclosure.

Metal enclosure 3D model

Rear view of assembled EEZ H24005 with top cover removed

Firmware

The EEZ H24005 firmware is an Arduino sketch that lets users perform all operations both locally and remotely. While local control via 3.2” TFT color touch-screen display allows quick on-site handling, remote control allows not just convenient access via serial/USB or Ethernet connection, but also makes it possible to automate many operations on single or multiple units in a classroom, laboratory, or so-called automated test facility.

Feature List

Feature Description
Development platform Arduino IDE 1.6 or later
Local display GUI development EEZ Studio
Remote control Yes, SCPI
User profiles 10, with auto-recall feature
Output values programming interface Touch-screen: keypad, step, slider; encoder knob (stretch goal 1)
Output mode Standard, Low-ripple (CPU controlled)
Calibration Voltage and Current (multiple steps wizard, user password protected)
Output coupling Yes (serial, parallel)
Output tracking Yes (voltage, current, power, all protections and limits)
Date/time Yes
Event logger Yes (info, warnings, and error conditions)
Statistics CPU and channel’s total/current working hours
Diagnostics Self-testing, fan, ADC measurements, calibration, protection tripping

Local Control

The main home screen provides a consolidated overview of all programmed and measured output values, the status of various protection mechanisms, and easy access to system settings, user profiles, event views, and input power control (Stand-by mode). Currently three different views are implemented as shown below, and these can be further expanded for specific user needs.

Main page views: 1. Numeric, 2. Horizontal bar, 3. Vertical bar, 4. YT view

The most frequently set options are programming output values (voltage and current) and changing power outputs. So we offer three ways of setting outputs: one that emulates a numeric keypad, an encoder (step mode), and a potentiometer (slider mode). The pot works as a 2D slider with variable “sensitivity,” allowing changes to a selected value in larger or smaller increments.

Programming output values: 1. Keypad mode, 2. Step mode, 3. 2D slider mode

Remote Control

Thanks to SCPI support, one or multiple EEZ H24005s can be controlled remotely via a serial (over USB) or Ethernet connection.

Remote controls: 1. Serial console (USB), 2. Telnet (Ethernet), 3. 3rd party SCPI controller (Ethernet)

Protection Mechanisms

EEZ H24005 comes with multiple protection systems that have been thoroughly tested using various types of loads and taking into accounts edge cases such as powering up, shut down, run-time detection of cooling fan failure, etc.

Protection mechanisms are implemented at both the hardware and software level to guard to provide the maximum possible protection for connected loads and the power supply itself. Currently, the following protections are provided:

  • Current limiting and over-current protection (OCP)
  • Voltage limiting and over-voltage protection (OVP)
  • Power limiting and over-power protection (OPP)
  • Over-temperature protection (OTP) per channel, system, and load/battery
  • Remote sensing for reverse polarity
  • Max. output current limitation when cooling fan failure is detected
  • Automatic enabling of OVP when remote voltage programming is selected
  • Automatic shutdown on power good or watchdog signal failure
  • Automatic output voltage or current balancing when channels are coupled in series or parallel
  • Automatic down-programmer disabling when excessive power sinking is detected
  • Shutdown when any of protections tripped
  • Switch off all outputs when any protection is tripped
  • Force disabling of all outputs on power up

To see the EEZ H24005 in action, check out our Videos page.

Assembly

The EEZ H24005 is available in several kits, from bare bones to complete kits. Assembling and using the power supply requires an understanding of electronic circuits and basic computer programming skills. We’ll be glad to assist anyone with the assembly process. Support can also be found in popular electronic forums where the project has already gotten a lot of attention (eevblog and the diyaudio forums ). Reaching out for help is the best way to avoid errors and frustration!

Pledge Levels

There are four pledge levels for this campaign:

Pledge level Bare PCBs Enclosure and Assemblies Core Modules Complete Kit
Set of 4 bare PCBs Yes n/a n/a
Metal enclosure Yes Yes
Nuts, bolts, and electromechanical parts Yes Yes
Wire harness Yes Yes
Set of 4 PCB modules Yes Yes
3.2” TFT color touch-screen Yes
2 x AC/DC power modules Yes
Arduino Due Yes

Manufacturing Plan

We have already successfully produced limited numbers of prototype PCBs and metal enclosures. We’ve chosen a manufacturer for the enclosure and are currently investigating manufacturers for the PCBs and PCBA. We will source wire harnesses and packaging locally.

All modules will be tested in-house before shipping. However, end users will need to complete calibration locally by following the simple calibration wizard or remotely using SCPI commands.

Risks & Challenges

We have been working on the EEZ H24005 for the last two years and are confident we have eliminated most of the technical risk. We’ve done this by completing four prototypes and getting lots of feedback and help from the communities on popular electronics forums. Similarly, the firmware is mature and complete for its core based functionality implementing SCPI and touch-screen interfaces. We are now working to add more nifty features.

There’s always a possibility of unforeseen delays with PCB module assembly due to some part shortage or shipping issue. However, we have built a margin into our schedule to allow for such unforeseen delays. We will of course let our backers know if there are any problems that could affect the ship date.

Shipping & Logistics

EEZ H24005 components will be shipping from Crowd Supply’s warehouse in the United States. We can’t pre-pay VAT, so if your country collects VAT upon import, you’ll likely have to pay that and possibly deal with customs clearance. Therefore, the stated shipping cost does not include any applicable taxes. Unfortunately, this applies to everyone, including EU backers, as we are not able to support a parallel EU logistics and accounting operation.

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Credits

Envox

Envox d.o.o. is home of the Envox Experimental Zone (EEZ), an open source initiative to bridge the gap between DIY / hobbyist / educational / low-budget and professional / commercial test and measurement solutions.


Denis Kotlar (a.k.a. prasimix)

Project Manager

Martin Vladic

Senior Software Developer


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