Black Globe Feeds

Black Globe, parked
Black Globe, parked

Here are the feeds from the black globe thermometer, currently parked in the Dream Factory (in the basement of the City of Edinburgh Methodist Church).    Obviously it’s a working space, so we can’t always leave it parked in a good location, scientifically!  At the moment it’s far too close to a wall, which will therefore have a disproportionate effect on its readings.  On the other hand, it should still work for looking at what happens when the heating goes off at night (assuming it does – if it doesn’t, that might be useful for our hosts to know!). If you can’t see anything, try a mouseover – that reveals settings buttons that might help. If that doesn’t work, then we’ve probably lost some part of the connection.

What we have up is one DHT22 – which is definitely taking ambient temperature – and two DS18B20s, one for ambient temperature and one inside the black globe. Because the One Wire libraries don’t guarantee any particular order for picking up the DS18B20s, and our data format doesn’t report the sensor address, we aren’t entirely sure which is which. The idea is that if one of the mystery temperatures matches the DHT22 and the other doesn’t, that tells us the non-matching one is the globe. A good scientist in the group did have us check that when out of the globe, all three give us the same temperature.I held what’s labelled as “ambient temperature DS18B20” towards the beginning, which might be the big spike – but as we observed hurriedly on Tuesday, the globe appeared sensitive even to people passing nearby.  A second touch test didn’t register. It could be the connection to the web service, since that doesn’t appear to go like clockwork like it does on Christ Church’s wifi.

Here’s my best guess – but don’t trust the labelling. I think the DS18B20 sensors could even swap feeds when the equipment falls over – which will be obvious from the missing data or from the twitter feed. We’ll change the data format “in the fullness of time” but meanwhile, I’ll hold the ambient DS18B20 and the DHT22 towards the beginning of each run.

2 thoughts on “Black Globe Feeds

  1. Either the hall has an extremely powerful heating and cooling system or the spike in temperatures recorded indicates a problem with our data collection system!
    This is really confirmed by the fact that the DS18B20 is a digital device (rather than an analogue device) and therefore should show discrete jumps of about 0.25 degrees rather that smooth lines. The charting program is filling in for the missing readings with a straight line – where the wireless communication has been lost.

    In spite of the above the charts demonstrate the collection of even basic temperature readings can give a good initial insight into the effectiveness of a heating system.

    1. The powerful heating system is my hand! It shows the feeds are correctly identified; the one marked black globe didn’t go up while I touched the other two. I think the graph is raw data points but with lines connecting them – hence the smooth line over when it was down – rather than averaged in any way. I need to download the data and look at it to be sure. My top priority is seeing if any position in the Dream Factory makes the black globe stop tracking the other readings. This is the first day away from a radiator, but It was warm inside with warm walls today, so the first real test might be this evening.

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