Hi,
I am planning to use emonTH for my project, however I need to use air-flow sensor beside Temp and humidity sensors.
Is it possible with the product? if yes can you suggest me a sensor type for the air-flow.
The air-flow sensor is used to tell me if the fan is working in the panel or not.
Looking toward your kind help :)
Re: emonTH sensor integration
I can think of 3 types of air flow sensor: a pressure plate, a cup anemometer, or a hot wire anemometer (or similar).
The last is impractical as it requires a (comparatively) very high current that would lead to an impossibly short battery life. The second requires a fairly precise mechanism (which you can purchase) and you need to detect pulses, which is difficult again from considerations of battery life. I think the easiest practical method is a pressure plate that operates a contact (which could be a magnetic reed switch for reliability). Though an industrial version can be bought (http://www.dwyer-inst.com/Product/AirQuality/AirFlowSwitches/ModelAAFS), you could very easily make one yourself - simply a hinged plate that is hung in the air flow, and which is moved away from its rest position when the fan is working.
On your emonTH, Dig 2 on the screw terminal block has a pull-down resistor of 10 kΩ fitted, so you could wire your switch between there and 3.3 V and poll it each time you take a reading. If that is too expensive in terms of battery life, you could instead wire the switch to the switched supply used by the temperature sensor Dig 5, making sure you read the switch while the power was on!