Wednesday, July 31, 2013

Zumo - Reflectance Sensor modification (remapping)

This sensor is pretty slick.  Pololu designed it to work out of the box with the Zumo Ardunio Shield.  However for my project, I need access to the sensor IO lines without going through any of the Ardunio A-Analog pins.

Sensor is not working post-modification.  My concern is if this is a multi-layer board such that I may have inadvertently a cut trace that may run under trace on the top layer? I suspect not given the proximity of the vias.

When powering up the board the Red LEDs no longer light and I have looked at the IR LEDs through two different cameras - seeing no IR light.

The enable terminal is in place, however the jumper is removed.  The Red LEDs were functioning prior to my cutting the traces for remapping.  In the picture I have soldered a resister on the IO line for each sensor.

I have been checking pin voltages and tracing everything.  Going to post a question on the Pololu form next.


  1. The LEDON MOSFET is the culprit.

    I have verified traces using a DMM based on the schematic and determined that the problem is with the mosfet. While by-passing (connecting the LED series gnd directly to gnd across what would be R9) the mosfet the LEDs are activated as expected. IR LEDs confirmed using camera trick.

    I reseeded the mosfet, no change. Perhaps the mosfet was damaged while either cutting the traces or soldering in new resisters on the IO pins on the reverse side. This would be unexpected.

    Alternatively perhaps an ESD event occurred across the device :-(


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