MaxEELabs · Bench Instrumentation
Upgrade the PSU Already on Your Bench
PSU-EXT is an inline hardware module and software stack that adds remote control, protection features, live telemetry, and interactive dashboards to a conventional bench power supply — no replacement instrument required.
Working EVT-stage prototype — watch it in action- Measures
- 0–25 V / 0–2.5 A
- Current resolution*
- 0.0001 A
- Control
- SCPI over USB & TCP
- PCB Footprint
- 100 × 50 mm
* Under lab conditions with a 0.256 V PGA setting and 64 SPS rate.
What's new?
DC Current Accuracy Spec Update
Our current-accuracy specification had been TBD. Not anymore.
After calibration, we compared PSU-EXT current readings with a RIGOL DM858E bench multimeter, and the results are exciting!
PSU-EXT measures current with 0.0001 A resolution. Our measured prototype accuracy is:
- ±(0.5% of reading + 0.5 mA) from 20 mA to 500 mA
- ±(1.5% of reading + 0.2 mA) from 1 mA to below 20 mA
Support PSU-EXT
A programmable PSU solves remote control by replacing the instrument you already own. PSU-EXT takes a different path: it adds the same capabilities to the PSU already on your bench.
| Aspect | A Programmable PSU | PSU-EXT |
|---|---|---|
| Your existing PSU | Replaced with a new instrument | Kept — extended in place |
| Openness | Closed firmware, fixed feature set | Open hardware, firmware, and software |
| Network control | Often USB-only, or LAN-only | SCPI over both USB and Wi-Fi |
| Automation | Whatever the vendor's own software supports | Built-in scripting IDE and reusable dashboard widgets |
| Instrument scope | Locked to that one instrument | Widgets adapt to other SCPI-capable gear too |
Applications
Connect the supply to PSU-EXT, connect the load or device under test to the output, and control or monitor the session from the browser interface.
Hardware & Firmware Developers
Show voltage, current, and power trends while a device boots, joins a network, writes flash, or enters sleep. Verify real power budgets and catch current spikes a front-panel meter would miss.
Repair Engineers
Use PSU-EXT as a controlled inline gate between the PSU and the device under test. Set over-voltage and over-current behavior, then switch the output on from the browser.
Battery Testing
Sit PSU-EXT between a battery and the load. Watch voltage, current, and power during discharge, and compare runtime across firmware modes as the battery voltage falls.
Makers & Hobbyists
Make voltage, current, and power visible in a browser dashboard for demos, livestreams, or project videos — without pointing a camera at a bench PSU display.
01 — Hardware
The Board
An inline unit that sits between the PSU and the load, with galvanic isolation between the control side and the measurement/output domain, plus firmware that owns acquisition, protection, and SCPI command handling on-device.
Board
- Operating range: 0-25 V and 0-2.5 A
- Standard 3/4 in (19.05 mm) spacing for 4 mm banana receptacles
- Relay-controlled output path for enable/disable
- Isolated measurement and control architecture (ISO1540 + RFM-0505S)
- ESP32-S3-N16R8 pre-certified MCU/wireless module
- INA240A2 current-sense amp + ADS1115 ADC front-end
- USB-C for control-side power/data, with data and power-path protection
- Two external trigger inputs
Onboard Firmware
- ESP-IDF firmware for ESP32-S3 with SCPI over USB CDC and raw TCP
- Two-point voltage and current calibration support
- 100 sample/second circular buffers for voltage, current, and power history
- Relay output control, OVP/OCP behavior, timer queues, and trigger actions
02 — Software
Software for Measurements
A browser dashboard for watching and controlling a session live — voltage, current, and power widgets, protection state, and a built-in SCPI console, all backed by a browser-safe proxy to the device.
- Browser-based operator interface for control, telemetry, and configuration
- Live voltage, current, and power widgets with local-history charts
- Protection widgets for OVP/OCP thresholds and state
- Built-in SCPI console with device selection and tagged logs
- Backend proxy for browser-safe access to USB CDC and TCP SCPI devices
03 — Automation
Scripting IDE
Automate with JavaScript from a built-in browser IDE. Write a measurement or control sequence, hit run, and a dedicated PC-side task runner executes it against real SCPI devices — with live progress, logging, and time-series recording, not just fire-and-forget commands.
- Built-in browser IDE — write, run, and debug scripts without leaving the dashboard
- Sandboxed execution — scripts get no filesystem, network, or host access
- Query and control any configured SCPI device with query(), write(), and queryBinary()
- Live progress, logs, and time-series measurements stream straight back into the IDE
- Save, tag, and reuse scripts from a built-in script library
- Built-in calibration and accuracy-measurement scripts, validated against reference instruments
const voltage = query("PSU1", "MEAS:VOLT?");
const current = query("PSU1", "MEAS:CURR?");
record(new Date(), "voltage", "V", voltage);
record(new Date(), "current", "A", current);
log("INFO", "Measured " + voltage + " V, " + current + " A");
progress(1.0);
return { voltage, current };Open Source
PSU-EXT is open across the hardware, firmware, backend, and frontend. The core materials are available now in the project GitHub organization.
PSU-Ext-Org
Browse all our repositories on GitHub
Keep the PSU You Already Own — Add the Rest
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