Recently we had to build a device able to measure temperature on a roof. No electricity was available up there, the only technological stuff we could use was a wifi network. That project is not really original since the issues involved have been covered in the mail box and the weather station posts. However we though you would be interested in the box construction....
In an computer system, measure and event timestamps are considered an evidence and, nowadays, no one expects to encounter difficulties in this domain. However, knowing the exact time at any time is far from obvious, in particular if you work with autonomous sensors with limited resources.
A few months ago, we explained how to configure a YoctoHub or a VirtualHub to automatically post sensor values on emoncms.org. Emoncms is a web site which allows you to store measures in the cloud and to display them prettily. There are numerous sites which offer this kind of services (either free or for a fee), but Emoncms is, to our knowledge, the only one which is Open Source and which can be installed on a private server. And this is exactly what we are going to do this week.
Summer is coming and, with it, heat waves that put a strain on the air conditioning of server rooms. How can we know if an air conditioner is of the right size or if it labors to cool the room and risks to fail at any time? How can we know if fresh air is distributed everywhere, or if the addition of a simple air circulator could save a few KWh?
CO2 sensors are increasingly popular to monitor air quality at home and in business premises. So much so that we tend to forget that the measures are based on rather advanced technologies, requiring some precautions if we want to make sure that we obtain valid measures. So, do we need to calibrate a CO2 sensor and, if we do, how should we do it?
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