USB Current Probe Extender

Having gotten two answers from two USB meters, I figured it was time to get primal:

USB Current-Probe Extender - wiring
USB Current-Probe Extender – wiring

That’s a pair of USB breakout connectors and lengths of nice silicone wire (24 AWG power & 28 AWG data), with just enough slack for a Tek A6302 current probe:

USB Current-Probe Extender - in action
USB Current-Probe Extender – in action

So I can see the actual current waveform of a Glass Tile box running from a bench power supply:

Tiles 2x2 - bench supply - 50 mA-div
Tiles 2×2 – bench supply – 50 mA-div

The top trace is the firmware heartbeat from the Arduino Nano, the middle trace is the SK6812 LED data stream, and the bottom trace is the USB current at 50 mA/div. The current steps downward by about 10 mA (just after the data burst) when one of the tiles changes color and and LED shuts off.

The current probe reveals some mysteries, such as this waveform from a dirt-cheap USB charger:

Tiles 2x2 - anon white charger - 50 mA-div
Tiles 2×2 – anon white charger – 50 mA-div

I wonder why it’s ramming 100 mA current spikes into the circuit, too. At least now I can see what’s going on.

6 thoughts on “USB Current Probe Extender

  1. Obviously it’s time to bust that dirt cheap charger open and see what’s in there. My guess is a resistor and seven silicon diodes in series, because Zeners cost money, people!

  2. The way the wires cross over each other in that first picture really had me scratching my head for a minute.

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