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8. Data Acquisition Board
The Data Acquisition Board is the electronic interface between devices such as a fuel cell, solar
panel and wind turbine. When connected to a computer via a USB cable, it measures and
computes voltage, current, resistance and power then transmits these electrical quantities 3 times
a second to the computer. The computer software displays these quantities as both numbers and
colored line plots as they are transmitted
.
Input and Output Connectors
There are two (2) Input connectors. One is colored red, which indicates positive or plus (+)
polarity and the other is colored black to indicate negative (–) polarity. In the following
experiments, power sources such as a battery, solar panel, wind turbine or fuel cell will be
connected to the Input connectors.
There are four (4) Output connectors, but they are actually two sets of positive and negative
connectors arranged in parallel - meaning that the two positive (red) terminals are connected
together and the two negative (black) terminals are connected together (but not to each other; i.e.,
positive to positive and negative to negative). In the following experiments loads such as a
resistor, capacitor, motor and fuel cell are used. (a fuel cell can be both a power source as well as
a load).
The diagram in the next subject line shows how these connectors are arranged.
1 Ohm Sense Resistor
A 1 ohm sense resistor (labeled R4 on the circuit board) is connected between the Input and
Output connectors. Its main purpose is to measure the current flow from the power source on the
Input connectors going into the load on the Output connectors. The sense resistor, R4, is also
attached to the microprocessor (U1), which does the work of "sensing" current and load
resistance.
Since the loads in the following experiments tend to be of small resistance values, generally 10
ohms, or less, the 1 ohm sense resistor must be considered in current and resistance calculations
(as will be shown later). An equivalent circuit is shown on the following page
:
10
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