Soil Moisture Meter

This device measures the moisture of the flower soil of your plants. If the moisture drops below a defined value, you are informed it's time to water the plants again. Using several of these devices (one for every plant), you don't have to worry anymore about your plants drying up.

The device uses a capacity sensor area to measure the moisture. Two square copper areas on the PCB serve as a plate capacitor. In contrast to a resistive measuring method, this sensor does not wear over time because of oxydizing. The values are therefore reproducible and accurate.

The first thing you want to do after installing the sensor is to initialize it. This is to tell the device which moisture level you define being "dry". You can start the initialization by pressing the button for some seconds. The LED will blink to indicate that the sequence is started. The device takes several measurements to calculate an accurate threshold. You can change the amount and time between measurements in the E2P configuration. The default is five measurements with 15 minutes time between. After all measurements are done, the device goes into normal operation mode.

In normal operation mode, the device measures the soil moisture after some hours of a deep sleep with only ~ 1.5µA power consumption. After several of these measurements (configurable in E2P), the device sends out the humidity as a value between 0 and 1000 permill. The range is automatically adjusted by remembering the maximum moisture level that happens in the current watering cycle. You will see that after watering your plant, the value will go high and then lower again when the soil gets dry. If the level hits 10%, it may be time to let your server software connected to your base station inform you somehow, maybe with an alarm of the RGB dimmer or by sending an email.

Supported Messages

• Generic_DeviceInfo_Status
• Generic_Battery_Status
• Weather_Humidity_Status

Offset	Block	Content	Type	Size	Description
0	Hardware Values for hardware setup, which have no special meaning to SHC device concepts + the DeviceType, which decides about the existence of further blocks.	DeviceType	EnumValue	1 Bytes	The device can check with this value if the EEPROM data is meant for the actual type of device. If not, the device goes into an error mode. Values: 0 = BaseStation, 10 = Proxy, 20 = EnvSensor, 40 = PowerSwitch, 45 = Controller, 50 = RGBDimmer, 60 = Dimmer, 70 = SoilMoistureMeter, 80 = Thermostat, 90 = TeaMaker
8		OsccalMode	IntValue	1 Bytes	This value is used to change the speed of the internal oscillator. 0 = don't use OSCCAL calibration (e.g. external crystal oszillator is used). -128 = OSCCAL measure mode: the LED blinks every 60s, so the user can measure the original speed. -127..+127 = The speed is adjusted by the given amount in per mill (e.g. 10 means to speed up the device by +1%). MinVal: -128, MaxVal: 127, Default: 0
16		Reserved		6 Bytes	n/a
64	Generic This block contains SHC configuration data which every device has.	DeviceID	UIntValue	12 Bits	The DeviceID identifies the specific unit in the SHC network. It is used to address the device and in messages the device sends. Every device has to have a different DeviceID. MinVal: 0, MaxVal: 4095
76		Reserved		4 Bits	n/a
80		PacketCounter	UIntValue	3 Bytes	The PacketCounter is counted up throughout the whole lifetime of the device and is used to make the encrypted packets differently from each other every time. MinVal: 0, MaxVal: 16777215
104		Reserved		19 Bytes	n/a
256		AesKey	ByteArray	32 Bytes	This key is used to encrypt packets before sending and also used as primary key to decrypt packets. Special devices may have additional keys in their device specific block.
512	SoilMoistureMeter This device can measure the humidity of soil to estimate if watering of plants is necessary.	WakeupIntervalInit	EnumValue	2 Bytes	Decide about the interval between two measurements when the device is in initialization mode (after button press) to remember the dry threshold value. Values: 1692 = 10s, 2421 = 1m, 2538 = 2m, 2794 = 4m, 3050 = 8m, 3292 = 15m, 3474 = 20m, 3548 = 30m, 3804 = 1h, 4060 = 2h, 4261 = 3h, 4316 = 4h, 4517 = 6h, 4572 = 8h, 4773 = 12h, 4828 = 16h, Default: 3050
528		AveragingIntervalInit	UIntValue	1 Bytes	The number of values whose average is calculated before the dry threshold is remembered. MinVal: 1, MaxVal: 16, Default: 6
536		WakeupInterval	EnumValue	2 Bytes	Decide after which time the device should be woken up by the RFM12B transceiver to measure values in normal operation. Values: 1692 = 10s, 2421 = 1m, 2538 = 2m, 2794 = 4m, 3050 = 8m, 3292 = 15m, 3474 = 20m, 3548 = 30m, 3804 = 1h, 4060 = 2h, 4261 = 3h, 4316 = 4h, 4517 = 6h, 4572 = 8h, 4773 = 12h, 4828 = 16h, Default: 3548
552		AveragingInterval	UIntValue	1 Bytes	The number of values whose average is calculated before the current humidity is calculated and sent. MinVal: 1, MaxVal: 16, Default: 6
560		DryThreshold	UIntValue	2 Bytes	This is the dry threshold and maximum counter value that should happen. MinVal: 0, MaxVal: 65535
576		MinVal	UIntValue	2 Bytes	This is the minimum counter value measured in the current watering cycle when the soil is wet. MinVal: 0, MaxVal: 65535
592		SmoothingPercentage	UIntValue	1 Bytes	This is the size of a moving window in which the absolute humidity (0 to 100 percent) is smoothed. This is necessary because the raw values typically show some short term variation, depending on external circumstances (plant in sunlight or above radiator). The variation also depends on the thickness of isolation above the sensor plates. MinVal: 0, MaxVal: 30, Default: 8
600		Reserved		949 Bytes	n/a