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interfaces:mh-sensor [2016/01/21 13:13] – created darroninterfaces:mh-sensor [2016/04/22 12:07] (current) – [Moisture detector] darron
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 ==== Flying Fish MH Sensor ==== ==== Flying Fish MH Sensor ====
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-{{:interfaces:mh-sensor.jpg?100}}+{{:interfaces:mh-sensor.jpg?200}} 
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 +{{:interfaces:ivy.jpg?200}}
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 and a pot to give both an analogue and digital (threshold) output. and a pot to give both an analogue and digital (threshold) output.
  
 +Various sensor configurations can be found which include an LDR, NTC thermistor, 
 +two resistive water/moisture detectors and more besides.
  
 +The water/moisture detectors utilise a 2 pin header which can allow us to reuse the
 +comparator board for any particular device we have available. For example, the top picture
 +shows a flat style 10K thermistor along with the moisture detector kit.
 +
 +Due to the circuit's simplicity, the digital output tends to oscillate when the
 +two inputs to the comparator have a similar magnitude.
 +===Schematic===
 +
 +This is a reversed engineered schematic, the capacitor values are unknown.
 +
 +{{:interfaces:mh-sensor.png?200}}
 +
 +===Moisture detector===
 +
 +After 3 months of use all I can say is this probe is mostly unusable, the
 +resistance value appears to be make little sense until at least you notice that
 +the probe is corroding. I have placed a second probe in the soil but this time
 +I have insulated the probe header (the other rusted) and now have the probe
 +against the inside edge of the pot rather than anywhere near the middle, maybe it will last longer...
 +
 +Conclusion. The moisture probes are a waste of time.