Revision as of 18:55, 18 April 2017

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The Power Monitor Board

Introduction

Based on the LTC2945, this board can measure Voltage, Current, and Power. Communication to the board to read out the values (among many other parameters) is done over a simple I2C interface. It uses a sense resistor to measure the current with varying degrees of resolution based on the value. The board has been designed to allow changeable sense resistors:

• 10 ohm = 10mA Max Current with 2.5uA Resolution
• 1ohm = 100mA Max Current with 25uA Resolution
• 0.1 ohm = 1A Max Current with 250uA Resolution
• 0.01 ohm = 10A Max Current with 2.5mA Resolution (ACTUALLY 5A MAX!) Though you 'could' measure 10A, that would burn up the 0.25W current sense resistor. If you need to measure higher than 5A, then you might be able to get a 0.01ohm resistor with a higher power rating.

Each of these resistors can be soldered onto a mini Current Sense Board, then based on the expected max current of the project, the appropriate Current Sense Board can be plugged into the Power Monitor Board.

Other features include min/max logging of the values, programmable alarm thresholds with dedicated alarm output(ALE), and an auxiliary 2.048V Analog Input (ADI).

Though, the board shows 3V3, the board is also compatible with 5V systems. This configuration from the datasheet was implemented:

Note: this board grounds both I2C address pins, so the address is 0xDE

Several options are available to connect this board into the project that's being measured:

• The headers - the 9 pin header on the left with ++++ and ---- connect in line with the positive supply to the project. x4 pins each are given to allow for higher currents. For example, connect the ++++ pins to the positive terminal of the power supply, then the ---- pins to the project.
• Terminal Block - the gerber silkscreen doesn't show this well, but near the bottom of the board, a terminal block can be mounted, then connect the (+) terminal (on the left) to the positive terminal, then the (-) terminal (on the right) to the project.
• Direct solder - instead of using the terminal block, wires can be soldered to these through-holes to be used as 'leads'.

Schematic

Purchase

Coming soon - given to Patrons ...

Parts

Assembly

Tutorial

Resources:
The forum post about the sleep modes