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158 lines
6.0 KiB
Markdown
158 lines
6.0 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/RAIN/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/RAIN/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/RAIN/blob/master/LICENSE)
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[](https://github.com/RobTillaart/RAIN/releases)
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# RAIN
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RAIN is an Arduino library for a rain sensor (analog).
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## Description
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A rain sensor (FC-37, YL-83, HM-RD) is a relative simple device.
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It measures the resistance of a number of wires when these are put in a liquid (water)
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The device converts the resistance to a voltage typical 0 .. 5 Volt.
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The more the wires are covered by the liquid, the lower the voltage.
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0.0 Volt is WET, and a high voltage is DRY.
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The breakout (LM393 comparator) I used to test also has a digital output,
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which goes LOW if a threshold (to be set with a potentiometer on the breakout) is reached.
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The library is EXPERIMENTAL as it needs more testing.
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(changes of the interface are definitely possible).
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## Hardware connection
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Typical connection
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```
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Processor LM393 SENSOR FC-37
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+-------------+ +----------+ +---------------------+
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| | | | | |
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| GND |----->| GND | | |
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| powerPin |----->| 5V |-----| |
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| analogIn |<-----| AO | | |
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| | | |-----| |
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| digital in |<-----| DO | | |
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| | | | | |
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+-------------+ +----------+ +---------------------+
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```
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## Interface
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- **RAIN(uint8_t port, uint8_t powerPin = 255)** constructor.
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port is the internal analog port to use.
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powerPin is optional, but recommended.
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- **bool begin(float maxVoltage, uint16_t maxSteps)** sets the ADC parameters.
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Allows to be changed runtime, e.g. if voltage fluctuates the math can be adapted by calling **begin()** again.
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Might be a separate **setVoltage()** is more efficient.
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- **float raw(uint8_t times = 1)** makes 1 or more measurements and averages them.
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returned value is the average number of ADC steps.
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- **float read(uint8_t times = 1)** makes 1 or more measurements, averages them and convert the average to a voltage.
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This voltage is returned, and also cached for **percentage()** and **getLevel()**.
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#### powerControl
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Will only work if the **powerPin** is set in the constructor.
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- **void powerOn()** switch the sensor on.
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- **void powerOff()** switch the sensor off.
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The powerPin is used to switch the LM393 ON and OFF so the sensor is powered
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only when the sensor is read. That reduces corrosion and energy usage.
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Note: when the power is OFF, the digital-out cannot be used e.g. for interrupts.
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So check what your project needs.
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Note: the powerOn() delays for 100us to give the LM393 time to stabilize.
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Adjust this if needed.
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#### Analysis
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- **void setDryReference(float dryRef)** used to calibrate the voltage when the sensor is dry.
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Use **read()** to read / calibrate the voltage when the sensor is dry.
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If not explicitly set, the max ADC voltage os used.
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- **void getDryReference()** returns the set value.
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- **float percentage()** returns the last **read()** to a percentage.
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Note one needs to call read() again to get a new value as this uses a cached value.
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- **float delta()** returns the delta voltage compared to previous read.
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It give the first derivative of the signal. How fast does it rise.
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- **bool setLevel(uint8_t nr, uint16_t millivolts)** allows a user to set 4 voltage levels in milliVolts.
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- **uint8_t getLevel()**
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Returns the level of the current cached voltage.
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See example.
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The library allows the user to set 4 thresholds or levels for the **getLevel()** function.
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These 4 levels + 1 zero level can help to control behaviour of a system at a certain level.
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Typical levels are almost empty, almost full and full.
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The level do not need to be on a linear mapping like 20% steps, if your project need
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other levels you can define these.
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Note it is possible to adjust the levels runTime with **setLevel()**
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#### MultiMap
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For a continuous mapping one can use the **MultiMap** library.
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It allows to map the voltage to any other useful unit as it can handle
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even non-linearities well.
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See https://github.com/RobTillaart/MultiMap
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## Operation
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The examples show the basic working of the functions of the library.
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The rain sensor can be used in different types of projects.
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Every project has a typical orientation of the sensor.
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| project | orientation | measurement |
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|:-----------------|:----------------:|:-------------:|
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| rain sensor | angle e.g. 45° | polling
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| leak detection | horizontal | interrupt - digital OUT
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| water level | vertical | polling
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For other applications it depends.
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## Future
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#### Must
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- update documentation
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- links etc.
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#### Should
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- optimizations
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- a lot of floats...==> more uint16_t millivolts? (0.2.0)
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#### Could
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- add unit-tests
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- make the number of levels configurable
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- dynamic array allocation.?
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- **float readExt(float voltage)** for external ADC
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- investigate level-changed "event"
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- investigate: **getLevel()** should it do a read()?
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- **setForcedRead(bool flag)** + getter
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- investigate "a scale of wetness"
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- investigate
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- different salinity
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- different liquids? which?
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- how linear is the device?
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#### Won't (unless requested)
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- example with multiMap
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- see multiMap library.
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- **incrLevel(nr, amount = 1)** + **decrLevel(nr, amount = 1)**
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to allow easier runtime tuning
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