Syringe Logic Probe, Revision 2

While my original probe is damned useful, it was a bit of a rushed job. Since then, I've found uncoated silver jewelry wire whose diameter is just a hair smaller than the inner diameter of the needle, allowing me to force it in for an electrical connection. More importantly, as I no longer solder to the outside of the needle, I can restore the safety cap and save my fingers from getting nicked.

--Travis Goodspeed
<travis at utk.edu>

Syringe Logic Probe

I hope my faithful readers will forgive a quick detour into electronic arts-n-crafts. Rest assured, I won't abandon assembly language to make toilet-paper covers and tea cozies. Instead I intend to demonstrate how a diabetic MacGyver would tap a difficult pin on a circuit board.

After building Sump's Logic Analyzer out of a spare Spartan 3 board, I needed a logic probe with a sharp tip. What's sharp enough to grab a pin on a QFP device or those microscopic columns of solder that are exposed around the perimeter of a QFN device? An insulin syringe, of course!

The tip is razer sharp, easily digging far enough into a pin to hold its place. A finger's weight on the plunger keeps the probe in place; it has never once slipped to short two pins, as my multimeter's probe is wont to do.

I haven't yet tested the probe's electrical properties at high frequencies, but it works well enough for sniffing AES keys from an SPI bus.


Cheers,
--Travis Goodspeed
<travis at utk.edu>