XO1.75 Tinderbox Power

This page describes the Tinderbox version of the XO-1.75 C2 laptop.

Power Distribution

The following diagram attempts to illustrate the XO-1.75 power distribution network, as well as the tinderbox measurement points:

Measurement Points

There are two types of measurement point in the above diagram. Most measure power passing through a particular point in the power distribution network, and are represented by a large X, along with an annotation of the voltmeter channel and measurement resistance. All measurement resistors have a tolerance (variation in resistance) of 1% or smaller.

A smaller number of points (2001, 2002, 2003, 2012) measure the voltage at a particular point in the power network. These are indicated by an arrow, and annotated solely with the voltmeter channel.

The definitive file describing this setup is the tinderbox configuration file.

Example Measurements

Example readings taken using this setup are available at http://dev.laptop.org/~wad/cl2_c2/. Some of these measurements are highlighted below.

Measurement Error

It should be cautioned that using a multiplexed voltmeter for measurement of power in a dynamic system has its downsides.

Laptop Off

When the laptop is off, the power measurements are quite low.

If DC power is supplied, but no battery is charging, the laptop takes a surprising amount of power.