As most of you know, I’m temporarily a bit unwell (although not as unwell as my laptop – time for a change!). I’ve decided that rather than try to soldier through, I’m just going to cancel the October sessions. That way at least you have advanced warning for the one that’s not today! Apologies, and we’ll see how it goes after that. I am up, though, for coffee or similar with anyone (new or old) who wants to talk or explore a building.
When I updated the SD cards to include heathackhub as a service (so that the pis would survive rebooting), I did it using the May 2016 Raspbian Jessie Lite, our first time with Jessie, I think. (“Lite” just means for headless and that doesn’t really matter here – it’s just smaller and more appropriate to how we deploy.) Unfortunately, I hadn’t realized that the Edimax EW-7811UN dongles we have don’t work with it, at least for us, but also for many other users.
Continue reading what’s up with the wifi
– and I think what I’ll do is bring along that phone/tablet app for us to look at, since at one point a good few people were interested in how that technology works. It’s really two apps – a really basic one for checking the internal weather conditions in a venue, and a little game about thermal comfort. I’ll need to remember the basics myself, but there’s always Google!
7:30 City of Edinburgh Methodist, in the basement –
Something about the building works at Christ Church tripped out their heating timeswitch and did a factory reset on it. I’m guessing there’s an internal battery that’s dead, as it’s relatively old. Unfortunately, it’s also a domestic model – and the defaults are for heating morning and evening. That’s a lot of gas to no effect – something we definitely want to avoid!
Continue reading …which reminds me, alerts –
… but the cycling round will take a little longer, I think. As will figuring out what level of my notebooks to transfer on line (and where) for the Cambridge-based folk; I aim to remove the guff from when I was still learning and making what I know available, but it’s the how!
With apologies, I’m unwell, and I won’t be able to make it out. On the other hand, I am working on getting the SD cards set up with the upgraded Pi image so that our setups can handle being power-cycled.
And I’m also having Tim’s code teach me how services work, so I can make the same kind of set-up for our second image – the one for monitoring electricity usage (helpful for debugging the random spikes and high periods one gets in community buildings!) whether it’s one or three phase.
While Christ Church Morningside’s hall is being refurbished, their Centre has a very different use pattern from usual, and we want to make sure everyone is well served. It’s a modern building with a nice big sunny window, but autumn is coming! Here’s the graph for it. This is actually the first time we’ve fielded a pi with the version of the webserver that restarts automatically when the power is cut – the documentation and process all works well, but if you update elsewhere in the field, be sure to leave enough time to make the required updates to the existing software (largely, npm packages).
Let’s see, what all did we do? Cleared up the mystery wiring diagram for the LCD display and agreed how to deal with it, taught me how to spec a current-limiting resistor, got further on thinking about how do we make the cheapest, low-skill data logger design we can, and thought about how we proceed in the longer term. That’s a lot!
So, the other piece of equipment I’ve been exploring is the cheap 4 digit LCD display – I think the one we have is the same as the Sparkfun one, but we got it from Proto-Pic. We’ll know what colour it is when we turn it on but I think it’s green! It has a common anode and 7 separate digital pins for the segments needed to show a single digit, plus a pin to select which digit to use – and then separate digital pins for apostrophe and colon, where the apostrophe kind of doubles as a degree symbol for some people. Multiplexing, pins numbered clockwise from the bottom right. Sounds simple enough!
- Proto-pic information with data sheet and sample code
- Sparkfun source
I’ve been looking at the basics on the Trinket – I can’t say I’ve mastered it, but here are some quick notes for absolute beginners like me! There are better technical sources of information, but this addresses some of our questions about how to make the lowest cost data logger possible on my kind of skill level.