USB Charger Doctor - In-line Voltage and Current Meter

USB pass-through dongle that measures voltage and current draw via a 0.05 Ω shunt resistor, displaying readings on a digital screen. Supports 3.5–7 V input and up to 3 A; alternates between voltage and current readouts every ~3 seconds. Data lines pass through unaffected.

Logical pinout · physical placement not verified

USB-A plug VBUS
USB upstream power input measured by the Charger Doctor. Adafruit states the dongle plugs between a USB device, supports 3.5-7VDC input, and has a 0.05 ohm resistor in line with the power pin to measure current draw.
Type · PowerVoltage · 3.5-7VDC input range from Adafruit product page; normal USB devices usually hover around 4.75-5.25V per source.
USB-A plug GND
USB upstream ground/reference for the inline USB power meter.
Type · Ground
USB-A plug D+
USB upstream data line passed through by the inline meter. Adafruit states the device passes the data lines through and supports USB 1.x and 2.x data speeds.
Type · Signal
USB-A plug D-
USB upstream data line passed through by the inline meter. Adafruit states the device passes the data lines through and supports USB 1.x and 2.x data speeds.
Type · Signal
USB-A receptacle VBUS
USB downstream power output to the connected device, monitored for voltage and current by the inline meter.
Type · PowerVoltage · 3.5-7VDC working range, up to 3A current, from Adafruit product page.
USB-A receptacle GND
USB downstream ground/reference for the connected device.
Type · Ground
USB-A receptacle D+
USB downstream data line passed through to the connected device.
Type · Signal
USB-A receptacle D-
USB downstream data line passed through to the connected device.
Type · Signal

Pin	Type	Function	Voltage
USB-A plug VBUS	Power	USB upstream power input measured by the Charger Doctor. Adafruit states the dongle plugs between a USB device, supports 3.5-7VDC input, and has a 0.05 ohm resistor in line with the power pin to measure current draw.	3.5-7VDC input range from Adafruit product page; normal USB devices usually hover around 4.75-5.25V per source.
USB-A plug GND	Ground	USB upstream ground/reference for the inline USB power meter.
USB-A plug D+	Signal	USB upstream data line passed through by the inline meter. Adafruit states the device passes the data lines through and supports USB 1.x and 2.x data speeds.
USB-A plug D-	Signal	USB upstream data line passed through by the inline meter. Adafruit states the device passes the data lines through and supports USB 1.x and 2.x data speeds.
USB-A receptacle VBUS	Power	USB downstream power output to the connected device, monitored for voltage and current by the inline meter.	3.5-7VDC working range, up to 3A current, from Adafruit product page.
USB-A receptacle GND	Ground	USB downstream ground/reference for the connected device.
USB-A receptacle D+	Signal	USB downstream data line passed through to the connected device.
USB-A receptacle D-	Signal	USB downstream data line passed through to the connected device.

Logical pinout · physical placement not verified

Pin details

8 connections

USB-A plug VBUS
USB upstream power input measured by the Charger Doctor. Adafruit states the dongle plugs between a USB device, supports 3.5-7VDC input, and has a 0.05 ohm resistor in line with the power pin to measure current draw.
PowerVoltage · 3.5-7VDC input range from Adafruit product page; normal USB devices usually hover around 4.75-5.25V per source.
USB-A plug GND
USB upstream ground/reference for the inline USB power meter.
Ground
USB-A plug D+
USB upstream data line passed through by the inline meter. Adafruit states the device passes the data lines through and supports USB 1.x and 2.x data speeds.
Signal
USB-A plug D-
USB upstream data line passed through by the inline meter. Adafruit states the device passes the data lines through and supports USB 1.x and 2.x data speeds.
Signal
USB-A receptacle VBUS
USB downstream power output to the connected device, monitored for voltage and current by the inline meter.
PowerVoltage · 3.5-7VDC working range, up to 3A current, from Adafruit product page.
USB-A receptacle GND
USB downstream ground/reference for the connected device.
Ground
USB-A receptacle D+
USB downstream data line passed through to the connected device.
Signal
USB-A receptacle D-
USB downstream data line passed through to the connected device.
Signal

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