USB VSense

USB VSense is a voltage indicator designed to provide insight into USB-powered devices quickly and simply. It works by giving you an unambiguous visual indication of its voltage mode with the help of illuminated, individually color-coded, and clearly labeled lights, one for each USB Power Delivery fixed-voltage mode, up to and including the latest 48 V and 5 A Extended Power Range (EPR) specs.

The unique features of USB VSense, such as its 6 mA maximum current draw and its 55 V input voltage, make it an ideal candidate for scenarios that require continuous voltage monitoring, as they allow you to confidently test a potentially hazardous voltage source before it can damage your devices. For instance, its ultra-low current draw allows you to leave USB VSense plugged into a USB hub indefinitely, where it will notify you of an overload with a clear blinking LED as soon as it detects one. USB VSense also diagnoses various USB power issues, helping you verify charger performance. It can quickly identify slow or faulty chargers, saving you time and frustration in day-to-day life.

Compact, Accurate, and Easy-to-Read

We came up with the idea of USB VSense while working on another project. We researched other USB power meters and discovered that they were often saddled with unnecessary features and were larger than they needed to be. So, we designed USB VSense using the “keep it simple” philosophy—this led to a streamlined product that is small, rugged, easily replicated, and still covers most USB power diagnostic situations you might encounter, including:

Figuring out whether a cable or a charger can provide sufficient power to your device.
Troubleshooting and detecting chargers that could potentially be unsafe or cause damage or unreliable behavior.
Determine your devices' power requirements and choose the right charger for them.
Ensure that your charger and device are compatible.
Act as a trustworthy development tool for USB power-related projects.

Voltage Info, at a Glance

With its simple array of LEDs, USB VSense has an individual annunciator for each USB Power Delivery voltage. Every indicator has a different color to make it easy to read and includes numerals. The following table demonstrates the range of lights and flashing patterns and what they mean:

Voltage Range	State of Annunciators
Lower than 10% of 5 V (E.g. 4.4 V)	5 V (red) rapidly blinking
Lower than 5% of 5 V but higher than 10% (E.g., 4.7 V)	5 V (red) slowly blinking
Higher than 5% of 12 V but lower than 10% (E.g., 13 V)	12 V (yellow) steady and 15 V (green) slowly blinking
Higher than 10% of 12 V but lower than average of 12 V and 15 V (E.g., 13.4 V)	12 V (yellow) steady and 15 V (green) rapidly blinking
Within 5% of 15 V (E.g. 15.1 V)	15 V (green) steady
Lower than 10% of 20 V but higher than average of 15 V and 20 V (E.g. 18.5 V)	15 V (green) rapidly blinking and 20 V (lime) steady
Lower than 5% of 20 V but higher than 10% (E.g. 19.5 V)	15 V (green) slowly blinking and 20 V (lime) steady
Above measuring capability (E.g. 52 V)	48 V (white) rapidly blinking

Features & Specifications

Fully capable of the latest USB PD EPR specifications (48 V, 5 A, 240 W)
A wide operational and measurement range of 4.5 V to 51 V
Individual color-coded indicators for each fixed voltage level:
- 5 V (red)
- 9 V (orange)
- 12 V (yellow)
- 15 V (green)
- 20 V (lime)
- 28 V (blue)
- 36 V (purple)
- 48 V (white)
Distinct alerts show > 5% and > 10% deviations from the fixed voltages. This feature is also helpful in approximating PPS voltages
Passthrough for USB 2.0 data, CC, and SBUS lines
Ultra-low power consumption, less than six mA of current drawn by the device (absolute maximum under regular operation)
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 20 V and 49 mV for voltages between 20 V and 51 V
Stacked PCB construction with high-quality parts built to last:
- Automotive grade LDO from Microchip (+70 V absolute max input voltage with ESD protection)
- Kingbright low-current LEDs
- JAE USB Type-C connectors rated for 48 V and 5 A
56 x 18.5 x 5.6 mm (2.28 x 0.73 x 0.22 in)

Comparisons

	USB VSense	ET920	FNB58	V&A Meter	Power-Z KM003C
Manufacturer	Meticulous Technologies	Klein Tools	FNIRSI	Plugable Technologies	ChargerLAB
Voltage Measurement Range	4.5 to 51 V	3 to 20 V	4 to 28 V	5 to 48 V	Up to 50 V
Current Measurement	No	Yes	Yes	Yes	Yes
Maximum Input Voltage	55 V	20 V ¹	28 V ¹	50 V	50 V ¹
Display Legibility	Excellent	Poor	Good	Poor	Good
Discernible Alerts	Yes	No	No	No	No
Internal Resistance	< 0.01 ohms	Unknown ¹	Unknown ¹	Unknown ¹	~0.02 ohms
Current Consumption	< 6 mA	Unknown ¹	Unknown ¹	Unknown ¹	< 50 mA
Dimensions (mm)	56 x 18.5 x 5.6 mm	75 x 50 x 15 mm	Unknown ¹	64 x 22.5 x ?? mm ¹	36.5 x 35.5 x 8.7 mm
Dimensions (in)	2.28 x 0.73 x 0.22 in	2.96 x 1.96 x 0.6 in	Unknown ¹	2.52 x 0.88 x ?? in ¹	1.44 x 1.4 x 0.34 in
Bluetooth/WiFi	No	No	Yes	No	Yes
Customizable	Hardware & software	No	No	No	No
Open Source	Hardware & software	No	No	No	No

¹ Assumed or absent value due to lack of specification from the manufacturer

Support & Documentation

"Open Source" isn’t a marketing buzzword for us — it is an invitation to learn. We are thrilled to make available the complete design files for USB VSense. We believe in contributing to the community by sharing knowledge.

We have selected specific licenses and applied for OSHWA certification to ensure this remains a resource for everyone, forever:

Hardware (CERN-OHL-S-2.0): A "strongly reciprocal" license that ensures any modifications to the hardware design remain open source and available to the community.
Firmware (GPL-3.0): A strong copyleft license that guarantees the code remains free to run, study, share, and modify.
Documentation (CC-BY-SA-4.0): Allows anyone to share and adapt our documentation, provided that credit is given and changes are shared under the same terms.

USB VSense was designed to be easy to repair and modify, featuring a stacked PCB "Oreo" construction; the entire device is made of PCBs. That means you can modify its appearance without a 3D printer, and its elegant design uses only four screws. With its open firmware, you’ll be able to make adjustments to add different blinking patterns or change the voltages if you desire.

Manufacturing Plan

USB VSense is ready for production. Leveraging its fully PCB-based design, we expect manufacturing to be highly streamlined.

We have entrusted PCBWay, a trusted partner with whom we have a long history, with the PCB fabrication and assembly. Each unit will be pre-loaded with test firmware to undergo initial factory validation, covering fundamental checks such as shorts, opens, component presence, and power-up. The units will then be shipped to our team for final firmware programming, rigorous testing, final assembly, and packaging. Once we place the order with PCBWay, we project it will take 8 to 10 weeks until the shipment is ready to be sent to Mouser.

Fulfillment & Logistics

After our production run is complete, we will package everything up and send it along to Crowd Supply’s fulfillment partner, Mouser Electronics, who will handle distribution to backers worldwide. You can learn more about Crowd Supply’s fulfillment service under Ordering, Paying, and Shipping in their guide.

Risks & Challenges

The arrival of a perfect storm cannot be foreseen, but every force that drives it can be mitigated. With this in mind, we have meticulously mapped every potential risk. Here are the key challenges we foresee and our plans to navigate them:

Defective Units: In any larger-scale manufacturing process, a small number of defective units is inevitable. To mitigate this, we have planned for preliminary factory testing to reduce the number of defects shipped to us. Furthermore, we will order additional units to compensate for any defective ones and ensure we can fulfil all rewards.
Import Tariffs: While tariff policies can be unpredictable, we have based our financial planning on current rates and included enough buffer in our funding goal to absorb potential cost fluctuations.
Component Shortages: To avoid supply chain issues, we have proactively selected components with stable, long-term availability. We actively monitor stock levels at all major distributors and have recently secured updated supplier quotations to ensure stable pricing and supply.

The successful production and testing of our initial 32 units has been invaluable. This batch has allowed us to refine our manufacturing instructions and gain critical foresight into potential defects, significantly de-risking the full production run.