I purchased an ALS-MPM-2F for a Bonsai self-watering project and my skillset is of a complete Newbie at the moment. I was wondering how best to implement this device on an Arduino - does it require its own power supply or can the Arduino drive this.
The product leaflet has written Power Supply: 3-5VDC, 12-36VDC ( standard ). I find this confusing.. can it run using Arduino's 3V or 5V pin or does it require something externally in the 12V to 36V range?
I'm assuming you'll need to get the 12V input down to 5V with two resistors if it was powered by a 12V source.
Could somebody post a wiring diagram of how they would read this device.
Would somebody be able to give me insight as to why one manufacturer would choose a 24V vs a 5V input for a device that ultimately does the same thing?
The sensor you first mentioned has an output signal of 4-20 mA. This is a standard industrial instrumentation signal. The measured parameter (0 to 5 meters water depth in this case) is converted to a mA signal with a range of 4 - 20 mA. This type of signal is preferable to a voltage output in an industrial setting because it is more resistant to external interference on long cable runs.
I found this as a typical illustration of how to wire such a device to an Arduino:
With that circuit the 250 ohm resistor converts the 4-20 mA into a 1-5 volt signal that the analog input can convert to an approximate 204 to 1023 binary value.
A statement in your sketch such as:
map(analogRead(waterLevelPin) 204,1023,0,5000);
Will yield the water depth in millimeters, with waterLevelPin representing the analog input pin your transducer is wired to.
The transducer from Seeed Studios appears to be a variant of the one you have that puts out a signal with a range of 0.5 to 4.5 volts approximately. This variant seems to require a 5.0 volt power supply.
