LOGGER-8-RS232: RS232 Soil Moisture Sensor Reader

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LOGGER-8-RS232:

RS232 Soil Moisture Sensor Reader - 8 Inputs

This low-cost no-frills data logger is perfect for reading up to 8 Vegetronix soil moisture sensors. It reports sensor data back to a host computer via RS232, or it can run stand alone and store data to non-volatile memory, for later retrieval.

LOGGER-8-RS232: 8 Input Data Logger

Setup is very quick, with screwless terminal blocks. It can powered with a wide supply range of 5 to 24V from batteries or a wall transformer.

Each sensor channel uses 3 spots on the terminal block: for power, ground and the sensor input. The logger will turn on power to all sensors simultaneously with a programmable setup time.

The device looks like a serial port to host PC systems so any communications software program such as HyperTerminal can be used to control it and gather data. HyperTerminal is standard to all windows systems so no additional host software need be purchased.

Data is returned in comma separated format, for easy manipulation in spread sheet programs. Here's an example output file: LoggerFormat.txt. Just configure the Windows HyperTerminal program to save data to a text file. You can specify unit labels for each channel, and each channel can be calibrated with a 2 to 10 point calibration curve for non-linear devices.

The logger can be used with sensors other than our soil moisture probes, so long as the sensors output less than 3.3V. For sensors with a higher output voltage, a simple resistor divider can be used to scale the voltage to appropriate levels for the logger.

The logger normally consumes only 85uA when it is not sampling data, so it is perfect for battery powered applications.

Applications

Sprinkler and irrigation systems.
Green house irrigation systems.
Home automation systems.
General purpose data logging.

Features

Monitors up to 8 sensors.
Streams data to a PC, or saves to internal non-volatile memory.
Real time clock.
Low power for battery powered operation.
Low cost.
Compact.
Screwless terminal blocks.
Flanged box for easy wall mounting.
Upgradeable firmware through RS232 port.
Each channel can be calibrated with up to a 10 point curve.

Other Vegetronix Products of Interest

Pricing and Ordering Info

For volume pricing contact us.

ORDER INFO
Part Number	Description	Price	Purchase
LOGGER-8-RS232	RS232 Soil Moisture Sensor Data Logger with 8 inputs.	$224.95

Specifications

LOGGER-8-RS232
Power consumption	85uA
Sample Bits	12
Supply voltage	5 to 24V supply
Dimensions	5.0"x2.5"x1.0" (12.7cm x 6.35cm x 2.54cm)
Number of sensor interfaces	8
Maximum sensor input voltage.	0 to 3.3V
Voltage to Sensors	Same as voltage input to unit.
Memory	91,900 8 channel records.
baud rate	9600
Temperature Range	-40°C to 85°C
Enclosure	Wall mounting bracket. Not waterproof.

Commands

The Logger doesn't come with any software. A serial communications program must be used to access the logger. We recommend Windows HyperTerminal, and only provide technical support if you are using HyperTerminal. This comes preinstalled on all XP and legacy Windows computers. If you are using a newer Windows OS such as Vista, see these instructions for setting up HyperTerminal.

The controller board may be configured, controlled and monitored by using the following commands. <CR> designates a carriage return.

Open HyperTerminal - Normally under Start/Programs/Accessories/Communications in Windows.

Set up the session for the appropriate comm port. Set the comm port setting to:115200 baud, 8-N-1. (Note if you have Rev 1.00 of the software the baud rate is 9600.) Set Hardware Flow Control to: none.

Data in flash memory is stored as a circular queue. When the memory is full, newer data will overwrite older records.

When the logger powers on. It may take up to 20 seconds for it to initialize the flash memory.

The default sample rate is once per minute. Power is applied across all sensor channels, and they are sampled at the same instant.

h<CR>	Displays the help menu.
v<CR>	Displays the current software version.
o<CR>	Toggle the streaming of data output, on or off. The default is to stream data out.
d<CR>	Returns the current date.
d [DD/MM/YYYY]<CR>	Sets the current date.
t<CR>	Returns the current time.
t [HH:MM:SS]<CR>	Sets the current time.
heart<CR>	Enable or disable the heartbeat LED. The purpose of the heart beat LED is to let you know that the board is running. The reason you would turn off the LED would be to conserve battery power.
u [sensor index] 'string[5]'<CR>	Sets the units of measurement for designated probe. Probes are numbered 1 to 8. Single quotes are necessary around the string. Use an empty string to remove units. For example ''.
p [secs]<CR>	Sets or returns the sensor power on time before sampling in seconds. This allows power to stabilize before sampling the sensors. All sensors are powered together.
c [sensor index]<CR>	Returns the probe calibration table for the specified sensor.
c [sensor index] clear<CR>	Clear the probe calibration table for the specified sensor. When no table is used the raw voltage sensed is returned.
c [sensor index] (X,Y)<CR>	Sets the probe calibration table. X is sensor voltage, Y is mapped value. From 2 to 10 points may be entered into the calibration table for each sensor. To enter multiple points just reinvoke this command for each point for the selected sensor. The logger will automatically sort the points by voltage.
s<CR>	Gets the sample period in minutes and seconds.
s [MM:SS]<CR>	Sets the sample period in minutes and seconds. Use 00:00 to turn off sampling.
e [Sensor index]<CR>	Toggles enable/disable for a designated sensor.
get<CR>	Retrieve all valid data starting with the oldest valid record and ending with the newest record. We use a slow baud rate to conserve power. Retrieving all data in the internal flash memory, may take up to an hour. Use a "q<CR>" to terminate this command.
dump<CR>	Dump all valid records stored in flash, in non-sequential order. This command normally is not invoked. Because of the slow baud rate, this command may take up to 2 hours. The only way to terminate the command before it completes is to remove power from the logger. Use a "q<CR>" to terminate this command.
del<CR>	Delete all data in the internal memory.
wipe<CR>	Erase all flash memory. Use this to purge old data.

Calibration Table and Units.

One of the cool features of the reader is how each channel can be programmed with up to a 10 point calibration table, so that the sensor can be linearized. If no calibration table is entered for a given sensor channel the reader returns the voltage for the channel.

If your sensor is linear, then only 2 calibration points are required. For example if 0.0V maps to 0, and 3V maps to 1.5 you would set up the calibration using the following command for sensor 2:

c 2 (0.0,0),(3,1.5)<CR>

In addition, you can specify the units for each channel as a string.

Wiring Table

Terminal Block TB1 (Sensor Inputs 1 and 2)
Pin	Description
1	Sensor 1: Power
2	Sensor 1: Input
3	Sensor 1: Gnd
4	Sensor 2: Power
5	Sensor 2: Input
6	Sensor 2: Gnd
Terminal Block TB2 (Sensor Inputs 3 and 4)
Pin	Description
1	Sensor 3: Power
2	Sensor 3: Input
3	Sensor 3: Gnd
4	Sensor 4: Power
5	Sensor 4: Input
6	Sensor 4: Gnd
Terminal Block TB3 (Sensor Inputs 5 and 6)
Pin	Description
1	Sensor 5: Power
2	Sensor 5: Input
3	Sensor 5: Gnd
4	Sensor 6: Power
5	Sensor 6: Input
6	Sensor 6: Gnd
Terminal Block TB4 (Sensor Inputs 7 and 8)
Pin	Description
1	Sensor 7: Power
2	Sensor 7: Input
3	Sensor 7: Gnd
4	Sensor 8: Power
5	Sensor 8: Input
6	Sensor 8: Gnd
Terminal Block TB5 (Power and Commons)
Pin	Description
1	Vin (5 to 24VDC)
2	GND

Firmware Upgrades via RS232 Port

The reader's firmware may be easily upgraded as new firmware versions become available. To upgrade the reader. Open up the reader box, and set the 2 jumpers on the board. Download the latest firmware and the VegeUpdater.exe program. Connect the reader to the RS232 port, and run the VegeUpdater.exe program in Windows. Remove the jumpers, and close up the box.

Trouble Shooting

Problem	Solution
The battery is wearing down after a couple of days.	Turn off the blinking LED.

Wireless Options

The logger will work with any point to point RS232 data radio/modem for remote monitoring. Digi Corp (was Maxstream) offers several suitable data radios. For example their XCite™ RF Modems work as an RF link to the RS232 Logger. Contact Digi Corp for details on their radios and their tech support.

How to Get Started

The best way to get started is to order a reader board and a few soil moisture probes and try them out in your application.

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