Data Acquisition Module is a low-cost, easy-to-use data acquisition system for measuring voltages, controlling and monitoring processes, and acquiring temperature data. Each of the 8 available channels can be configured for any of the digital, analog, or temperature modes via single-byte commands.
All operational power is taken from the host PC via the USB port. The mode of each I/O is automatically changed with each command sent. For example, if an I/O is set to Digital Output – High and then the Digital Input Mode is selected, the I/O is first changed to Input Mode and then the high/low state is read and returned to the host.
- 8 Channels configurable for Digital I/O, Analog In & Temperature
- USB Port Powered
- Low Cost
- Small Footprint; Easily Fits on Desktop
- Easy to Use with Single-Byte Commands - Can Utilize a Simple Terminal Emulator to Control All Functions or develop a custom software
- Data Acquisition
- Industrial/Process Control
- Process Monitoring
- 4-20mA current loop process monitoring
- Machine Control
- PC Data Logger
The unit is a 5-volt system that derives its power from the host USB port. This USB +5V is also available at terminal for various powering application. Each channel has the following capabilities:
Digital Output: Set IO high(5V) or low(0V).
Digital Input: Read the high/low state of any IO.
Analog In: Read and return the voltage on each I/O pin using a 10-bit A/D: 0-5 volt range.
Temperature: Measure temperature using a digital temperature sensor (purchased separately) in the range of 67 to 257°F (-55 to 125°C).
Using the Board
Simply connect the board to the PC to initiate the loading of USB drivers. Once the drivers are loaded, the unit is ready for use. All commands are single-byte commands.
You can either utilize a simple terminal emulator program, or write your own program in your language of choice. Begin by opening the COM port, set the baud rate to 9600, and send single-byte commands as shown in following Table. The Ping command can be used to locate the correct COM port used for communicating with the board, or you can look in Device Manager to see which port was assigned by Windows.
Interfacing with board
Push to On Switch – If you wish to connect a push to on switch to any of the IO1 to 8 then you can use this method. When switch is off the 10K resistor will keep the IO pin high, When switch is pressed on the switch will ground the IO pin. You can use digital input command to read this status.
– Any IO can be connected with LED like below. You can use digital output set high/low command to set status of LED.
– Self Oscillating type buzzer(piezo or coil type) can be connected to any IO. If using coil type buzzer, a diode should be used across buzzer to discharge its coil of high voltage during operation. In following diagram making a pin low will cause the buzzer to sound. Making an IO high will switch off the buzzer. Alternately you can also connect buzzer between IO and GND pin.
Measure Temperature using LM35 Sensor- LM35 is a temperature sensor will gives analog voltage for 10mV per degree Celsius. At 25°C you get 250mV output analog voltage. If you read the voltage with the board using analog read command you will get for example 0.250V output.
Since the sensor outputs analog voltage the wire connect to sensor & board cannot be more than 2 meters. In next method we will show how to measure temperature at over distance of 300 feet using CAT5 cable and DS18B20 temperature sensor.
Measure Temperature using DS18B20 Temperature Sensor
DS18B20 can be connected to measure temperatures from -55°C to +125°C (-67°F to +257°F) with ±0.5°C Accuracy from -10°C to +85°C
Up to eight DS18B20 digital temperature sensors can be connected to the board. The length of cable can be upto 300 feet(100 meters). For best performance, use Cat 5 type computer cable(also called Ethernet/LAN Cable) to connect the sensors to the board. Two pairs of wires in the Cat 5 cable are required for the connection. The first pair is for Power (5V) and Ground, and the second pair is designated as Data and Ground. In addition, a pull-up resistor is required for the data line of approximately 1K Ohms.
Reading Temperature will return valid temperature data if a temperature sensor is connected to the specified I/O port. If no sensor is connected, a Temperature command will always return 999.99°.
Cat5 cable lengths of greater that 100 feet may require a pullup resistor value of less than 1K Ohms
in order to achieve usable rise times at the sensor. The minimum safe resistance for the pullup resistor is 240 Ohms.
Sending read temperature command will returns current temperature in Celsius and Fahrenheit
Example reading: 31.8°C 89.24°F
4-20ma Current Loop - Many industrial systems uses current signals to monitor certain devices (like pressure sensors, gas detectors, temperature sensors). The signal is transported over 2 wires. The advantage of working with currents is a current always remains the same, no matter what the length of a wire is.
This method below allows you to log a 4 - 20mA signal coming from a sensor. The 4-20mA current is converted into voltage in range of 0-5V. Read analog values on the channel where this signal is connected. When the current is 4mA the board will read analog voltage as 0.88V, When the current is 20mA the board will read 4.4V
USB Interface is easy to use as it installs as Virtual Com Port to which any software working with serial port can connect.