EEZ Bench Box 3

by Envox

Modular, open-source test & measurement chassis

View all updates Feb 19, 2020

Two New Peripheral Modules (and More Delays...)

by Denis Kotlar (a.k.a. prasimix)

The main news for this update is that our TFT display supplier in China has announced an additional three to four week delay due to the Coronavirus outbreak. Unfortunately, they cannot yet provide a delivery estimate or let us know when production will stabilize.

We spent a little time looking for an alternative but did not find any suppliers with sufficient quantity. We have not received any information regarding the AC/DC converters, as the supplier’s office will remain closed until February 20th. The status of the Ethernet patch cables is also unknown.

Going back to Europe, the situation is as follows:

  • Our PCBA manufacturer is still waiting for PCBs; about 5% of components are still missing.
  • Work on the wire harness is progressing well.
  • The enclosures are nearing completion, with just the front- and rear-panel silkscreens yet to be added.

New Peripheral Module Designs

In the meantime, we have designed new two peripheral modules, which are now ready for prototyping. They are very simple: one, called PREL6, features six power relays; and the other, called SMX46, is a 4 x 6 switch matrix made with signal relays. The SMX46 also includes a power relay and two analog outputs. Both modules have two things in common: an entry-level on-board MCU and a front-panel connector (see below).

It is possible to mount two 16-pin, dual row, 3.81 mm connectors on the front panel of each new module. They support sockets with various number of pins (such as the 8-pin, push-in sockets shown above) and various form factors (push-in, screw-in, etc.). A few different manufactures – including WE and Weidmueller – offer these sockets, and cheaper versions are available on Alibaba and elsewhere.

The functionality of either module could be implemented with I/O expanders such as the MCP23S08 or the MCP23S17, but we found the entry-level STM32F030 MCU more compelling, as it falls within the same price range while offering greater programming freedom and additional features, such as PWM generation. Since BB3’s on-board firmware downloading procedure is completely automated (i.e. the master MCU will do it for you with just a few clicks) we see no reason not to use an MCU instead of an I/O expander.

EEZ DIB PREL6 Peripheral Module

Quick facts:

  • 4 x SPDT relays, max. 8 A / 230 Vac
  • 2 x SPST relays, max. 8 A / 230 Vac
  • On-board +3.3 V LDO
  • STM32F030 MCU
  • Firmware download via UART
  • Optional SWD for debugging
  • I2C EEPROM for storing board specific parameters
  • Dimensions: 146 x 95 mm, 2-layer PCB

Source files are available on GitHub.

EEZ DIB SMX46 Peripheral Module

Quick facts:

  • 24 x SPDT relays, max. 2 A
  • 1 x power relay, max. 8 A / 230 Vac
  • 2 x DAC output 0 - 10 V
  • On-board +3.3 V LDO
  • STM32F030 MCU
  • Firmware download via UART
  • Optional SWD for debugging
  • I2C EEPROM for storing board specific parameters
  • Dimensions: 146 x 95 mm, 2-layer PCB

Source files are available on GitHub.

Both modules will be programmed from the local TFT touchscreen display or remotely through a new set of SCPI commands for which we still need to add support. They will be also accessible via MQTT.

About the Author

Denis Kotlar (a.k.a. prasimix)


$154,699 raised

of $85,000 goal

181% Funded! Order Below

Product Choices


Support EEZ Studio Development

EEZ Studio is a cross-platform free and open source BB3 development environment but also attractive SCPI controller that is used to access many T&M devices using SCPI commands. Its development and support cost us money and your donation will help us to keep it alive and kicking.


BB3 - Starter (Without Peripheral Modules)

A BB3 enclosure kit without bare PCBs but with fully-assembled core modules (AUX-PS, MCU STM32F7, and BP3C DIB 3-slot backplane). The Starter provides an environment for experimenters who are willing to build their own modules or who want a specific BB3 configuration (such as a six-channel BB3).


BB3 - Two Channel (Full)

A BB3 starter kit and two full-featured DCP405 single-channel (40 V, 5 A) peripheral power modules, including an AC/DC power module for each. A two-channel programmable power source with advanced features: remote sensing, remote programming, a down-programmer, and additional OVP (with crowbar).


BB3 - Four Channel (Full)

A BB3 starter kit, two full-featured DCP405 single-channel (40 V, 5 A) peripheral power modules, and one dual-channel DCM220 peripheral power module. Includes all three necessary AC/DC modules. This is the two-channel full kit, expanded to include two additional programmable power sources.


DCP405 One Channel Module (Full)

A full-featured DCP405 single-channel (40 V, 5 A) peripheral power module with remote sensing, remote programming, a down-programmer and crowbar OVP. Includes an AC/DC module.


DCM220 Two Channel Module

A DCM220 dual-channel (2 x 20 V, 4 A) peripheral power module and its AC/DC module.


Cable Set

Two pairs of high quality, silicone, color marked (black-red), 1 m connecting cables; a pair of clip-on probes; and a pair of insulated crocodile clips.


BB3 Enclosure & Bare Boards

A BB3 enclosure kit with a wire harness, nuts and bolts for the three core modules, a 4.3" TFT touchscreen display, an encoder knob, and an 80 mm fan. Includes a set of bare PCBs for building the three core modules (AUX-PS, MCU STM32F7, and BP3C DIB 3-slot backplane) as well as PCBs for building one DCM220 two-channel peripheral power module and two single-channel peripheral power modules (either the DCP405 or the DCP405B, as they can be assembled using the same PCB). Suitable for builders with the necessary skill, time, and patience.



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)

Martin Vladic

Mouser Electronics

Component Provider

TME Electronic Components

Components & Hardware Sourcing

Jedinstvo - Kartonaža d.o.o.


Printing & Packaging

Drives and Motors d.o.o.


PCB & PCBA Manufacturing

See Also

Subscribe to the Crowd Supply newsletter, highlighting the latest creators and projects: