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Building an occupancy sensor with a $5 ESP32 and a serverless DB

matthew.science

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Re: Building an occupancy sensor with a $5 ESP32 and a serverless DB

#41

Post by chasd00 »

SCUSKU wrote: post #21

Awesome write up, I liked how accessible the writing is, as well as the fun tone. I have a problem where I will need to monitor the soil moisture of 20 trees in San Francisco. My current thought is to strap an ESP32, Lora module, battery, and capacitive soil moisture sensor and to send data once every 6 hours or so. I was wondering if off the cuff you have any suggestions or pointers on how to best approach this. Tha…

look at Adafruit's Feather line up. they have lipo support + charging and then an easy connector to use for i2c which you'll probably be using to interface to the sensor. You can probably find one with Lora included.

Re: Building an occupancy sensor with a $5 ESP32 and a serverless DB

#42

Post by sodality2 »

lormayna wrote: post #32

Can you use the variation of RSSI to track movement? I know thst it's multipath and cannot be really reliable, but maybe it can provide some useful information. Or maybe using 2 tracking devices and correlate the results.

Instead of triangulation like that, which could get real complicated, you could also simply place enough in the areas you’re counting and limit the RSSI cut-off enough to measure those right next to it. That would work for specific areas you want to measure trends in, instead of general 3d spatial triangulation.

though some of the papers I read did this via measuring the time of flight of BT packets and how they were changed when people walked between them, and that really blew my mind!

Re: Building an occupancy sensor with a $5 ESP32 and a serverless DB

#43

Post by davidw »

How do people "productize" their ESP32 projects? (Edit: not talking about mass-producing something, I just want a self-contained unit rather than a board with a bunch of wires sticking out)

I see a lot of pages where they show some bare-looking board, but in the real world you want to package that up.

If you're a software guy like me, you would likely prefer to pay a bit extra to just have that tidied up for you rather than fiddle around with stuff.

Re: Building an occupancy sensor with a $5 ESP32 and a serverless DB

#45

Post by lostapathy »

davidw wrote: post #43

How do people "productize" their ESP32 projects? (Edit: not talking about mass-producing something, I just want a self-contained unit rather than a board with a bunch of wires sticking out) I see a lot of pages where they show some bare-looking board, but in the real world you want to package that up. If you're a software guy like me, you would likely prefer to pay a bit extra to just have that tidied up for you rath…

3d printed enclosure?

Re: Building an occupancy sensor with a $5 ESP32 and a serverless DB

#46

Post by sodality2 »

epcoa wrote: post #39

> and heap thrashing since we're allocating and deallocating the result structure every single callback. This should not an issue. It is entirely possible to write this without any dynamic allocation (other than stack) at all, or it could be done be done with an arena. Consider with something as powerful as an esp32 a hash table is not even strictly necessary, surely for a single purpose use case like this.

I figure the internal data structure that already exists in the BT library probably uses something similar to a hash table, so I emulated it with less of the data being saved (just a MAC). You’re right though, there are smaller choices for data structures. I ended up upgrading to a better board with more memory, and just used the existing structure in the BT library. It fixed a number of other problems at the same time.

Re: Building an occupancy sensor with a $5 ESP32 and a serverless DB

#47

Post by davidw »

lostapathy wrote: post #45
davidw wrote: post #43

How do people "productize" their ESP32 projects? (Edit: not talking about mass-producing something, I just want a self-contained unit rather than a board with a bunch of wires sticking out) I see a lot of pages where they show some bare-looking board, but in the real world you want to package that up. If you're a software guy like me, you would likely prefer to pay a bit extra to just have that tidied up for you rath…

3d printed enclosure?

That sounds like one of those "I have a problem... now I have two problems" jokes.

I wanted something simple and cheap and now I need to go deal with this whole other thing I don't know much about and either rent or buy into it?

Re: Building an occupancy sensor with a $5 ESP32 and a serverless DB

#49

Post by bluGill »

davidw wrote: post #43

How do people "productize" their ESP32 projects? (Edit: not talking about mass-producing something, I just want a self-contained unit rather than a board with a bunch of wires sticking out) I see a lot of pages where they show some bare-looking board, but in the real world you want to package that up. If you're a software guy like me, you would likely prefer to pay a bit extra to just have that tidied up for you rath…

There are lots of options. Most of what you see they don't: this is a one off project for the hacker and if others find it useful great, but not the goal. As such packaging isn't needed, sometimes you shove it in a box.

If you want something nice, that can be done, now you need to pay someone (could be yourself!) to design a package. ESP32 is designed to be easy to put into your own products, this means design a circuit board and case to fit each other, and so on. Then you buy the ESP32 chips in bulk and assemble them onto the circuit board. The board you buy for a prototype is officially only a reference board and not what they expect you to ship (though shipping the board is common: they are small, cheap, and someone else did the hard board design)

Re: Building an occupancy sensor with a $5 ESP32 and a serverless DB

#50

Post by krasin »

davidw wrote: post #47
lostapathy wrote: post #45

Earlier quoted context omitted.

3d printed enclosure?

That sounds like one of those "I have a problem... now I have two problems" jokes. I wanted something simple and cheap and now I need to go deal with this whole other thing I don't know much about and either rent or buy into it?

JLCPCB would 3d print high-quality enclosures from a variety of UV resins: https://3d.jlcpcb.com/ and decently cheap.

The next best option is injection molding with PCBWay (or other similar provider): https://www.pcbway.com/rapid-prototyping/manufacture/?type=4...

An alternative is a sheet metal enclosure: https://www.pcbway.com/rapid-prototyping/manufacture/?type=4...

But 3d printing with JLCPCB is really the most convenient way unless you need a lot of parts (thousands) or the material properties of the UV resins would not be enough (high-temperature, outdoors, etc).

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