I'm planning to build a wireless temperature sensor to assist someone in their hobby, brewing beer. Periodic temperature report is all that's required, no control at this stage.
I bought the NRF24L01+ kit, so the next steps are:
As you can see, the plan is very rough so far. And I haven't used SPI before so I'm not sure of the range or what I'll need on the linux side.
Hmm. Sounds good - next step is trying to control the temperature, any maybe counting bubbles :)
Hope that helps - happy brewing :)
Heh, excellent bubble counter. Thanks for the suggestions.
Happy to contribute any code that others might find useful - will take a look at what's required.
Li-Ion bateries (I mean for example those used in cellphones) are affected by self-discharging process (up to 2% per month). Of course it is much better than in older NiMH batteries but anyway we may get much more electricity than we expect after a few months.
Also battery age is important when we consider reusing of old phone batterry - the potential capacity might be also affected seriously.
Of course instead of "may get much more" I meant "may get much less"
@motter, nice project. Remember to make the sensor "food grade" when putting it in stuff you are going to ingest :) Adafruit carries both a waterproof ds18b20 and food grade tubing. You'd want something like that.
Is the brewery within wifi range?
Using a CC3000, and having it post the data by periodically connecting and firing off an HTTP request containing the data might make the computer side of it easier. Wouldn't do any favors for the battery life (WiFi draws a fair amount of current, though you can and should keep it turned off most of the time).
I'd rather write a PHP/etc script to extract the data from the request than figure out how to get an obscure piece of network hardware meant for comparatively primitive systems working on any desktop computer, let alone linux....
Since it's a stationary installation, you don't even need lipo batteries... 3 or 4 NiMH AA's would be fine (careful with input voltage to CC30oo), and would have the advantage of being cheap to replace, chargeable with normal battery chargers, and alkalines could be used in a pinch (the beer must flow!).Whether this would be cheaper, I don't know. Remember, since there's no mains, you'll need at least two sets of batteries to keep this running. And maybe a juicy cap across the batteries so it doesn't reset when you swap the batteries...
Or you might be able to use a solar powered USB battery pack. They're pretty cheap now. I'm not sure quite how much power the panels produce but I'd imagine it should be enough to keep WiFi up for 30 seconds a day.
I'm quite interested in SPI for other reasons and already have the module, but it's worth bearing 802.11 in mind if it proves difficult.
In theory it shouldn't matter if it's reset when the batteries are changed (as long as it can reconnect) since whatever persists the readings will use its own clock.
@motter For your temperature sensor, checkout https://www.atlas-scientific.com/product_pages/sensors/env-tmp.html and for an example on how to get the temp probe to work with the espruino, http://forum.espruino.com/conversations/680/newest/ .
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