Mini review of USB Vsense USB PD voltage indicator

I’ve just received a sample of Meticulous Technologies’ USB VSense USB PD voltage indicator for review. It’s a simple device with two USB-C ports and color-coded LEDs showing the voltage supported from 5V up to 48V as defined in the Extended Power Range (EPR) specs.

In this mini review, I’ll go through the specs, a teardown, and test it under various scenarios using a range of USB-C power adapters and devices such as a Raspberry Pi 5 SBC, Radxa Orion O6 mini-ITX motherboard, and ASUS Vivobook 16 laptop.

USB Vsense specifications

• Fully capable of the latest USB PD EPR specifications up to 48V/5A (240 W)
• 2x USB Type-C ports – Passthrough for USB 2.0 data, CC, and SBUS lines; rated for 48V/5A
• Operational and measurement range
  • 4.5V to 51V DC
  • ATtiny 406’s 10-bit ADC with 4.3 V internal voltage reference provides stable measurements of up to 22 mV resolution for voltages below 20V and 49 mV for voltages between 20V and 51V
  • Automotive-grade LDO from Microchip (+70 V absolute max input voltage with ESD protection)
• Color-coded indicators (Kingbright low-current LEDs) for each fixed voltage level
  • 5V (red)
  • 9V (orange)
  • 12V (yellow)
  • 15V (green)
  • 20V (lime)
  • 28V (blue)
  • 36V (purple)
  • 48V (white)
  • Behavior
    • Steady within 5% range, or slowly blinking 5% under reference voltage, rapidly blinking 10% under reference voltage;
    • Higher than 5% of the reference voltage but lower than 10%, the next LED is slowly blinking. e.g.: Higher than 5% of 12V but lower than 10% -> 12V (yellow) steady and 15V (green) slowly blinking
    • Higher than 10% of the reference voltage, but lower than the average between the two LEDs, the next LED is slowly blinking. e.g.: Higher than 10% of 12 V but lower than the average of 12V and 15V ->  12 V (yellow) steady and 15 V (green) rapidly blinking
    • Etc…
• Power consumption – <- 6 mA of current
• Dimensions – 56 x 18.5 x 5.6 mm

USB VSense will be fully open-source, and both its hardware and firmware will be available once the funding goal is reached on Crowd Supply.

Unboxing and teardown

I received not one, but three USB Vense devices. Each features a USB-C male port to insert into the target device, a USB-C female port for the cable from the USB-C power supply, and eight LEDS for 5V, 9V, 12V, 12V, 20V, 28V, 36V, and 48V.

The design feels sturdy, as if it were housed in a metal enclosure, but instead, the device is multi-layered, made of several PCBs.

There are seven layers in total, with the part on the right comprised of two PCBs assembled together.

The 4th layer does all the job with eight LEDs and an AT406-N TH chip, which is the ATtiny406 microcontroller referenced in the specifications.

Testing USB Vsense

Time to do a few tests. I’ll use various target devices and three USB power adapters. An official 5V/3 power adapter I got with a Raspberry Pi 4, a 100W MINIX NEO P2 GaN power adapter, and an official 5V/5A power adapter for the Raspberry Pi 5.

I first tested a headless Raspberry Pi 5 with the 5V/5A power supply.

USB Vsense’s 5V LED was steady. So I connected a USB 3.0 drive and ran a stress test on all four Cortex-A76 cores, and it stayed steady, meaning the voltage was within 5V +/-5% (4.75 to 5.25V) at all times.

I then switched to the 5V/3A power adapter, and the 5V LED was steady, while the 9V was blinking at idle. This should indicate the voltage is over 5.25V, but lower than 5.5V.

When I ran a stress test, the 9V LED stopped blinking, meaning the voltage dropped within the 4.75V to 5.25V range.

I then did a quick test with the Radxa Orion O6 motherboard and the MINIX NEO P2 adapter, and the voltage was negotiated at 20V, as expected, since this is the maximum for the adapter.

I did the same with the ASUS Vivobook 16 laptop, and the voltage was also 20V (steady LED).

That’s until I ran a stress test on the laptop, and while the 20V was still steady, the 15V LED blinked slowly, meaning the voltage dropped between 18V (-10%) and 19V (-5%).

I did a final test using the 5V/5A Raspberry Pi 5 adapter with my laptop, and I was surprised to see 15V. I had forgotten that’s a proper USB PD adapter used at 5V with the Pi 5, but capable of up to 15V/1.8A as clearly marked in the adapter itself. It stayed steady during a stress test.

The USB Vsense is a nice little diagnostic tool to quickly check potential USB power issues like voltage drops. I’d like to thank Meticulous Technologies for sending a few samples of the USB VSense for review. It’s listed on Crowd Supply, but the crowdfunding campaign has not started yet.

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