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29

DOORS!!! I don't know if it is in the scope of your question but you can't imagine the wasted energy of opening/closing a door! A French comic strip named Gaston Lagaffe written in 1970 introduced a person who harvested the energy of an opening door to press oranges, print a picture, make coffee,... EDIT, thanks to to Olivier Dulac's comment I was able to ...


25

Absolutely, because: A secure device and channel means that you can trust the data. Yes, the actual temperature is not very private, but an attacker can provide false temperatures and cause an undesirable response (e.g turning heating on unneccesarily). This is how stuxnet worked, by misreporting the speed of the centrifuges, causing the control system to ...


18

Solar energy is even indoors an alternative to thermal and vibrational energy harvesting. This indoor photovoltaics use both the natural light and artificial light. On the Feasibility of Indoor Light Energy Harvesting for Wireless Sensor Networks (Carlos Carvalho and Nuno Paulino) discusses indoor light energy harvesting of the attenuated natural ...


16

You can hook up a USB battery pack to both the Pi and the charger (as long as it is designed to charge while being used) and if the power goes out the USB battery pack will take over powering the Pi directly. Search for "USB UPS" and you will find tons of info on individual setups.


13

In a comment to the original question, the OP suggests that an accurate count of people might not be needed, but the goal is rather to be able to detect an unusual amassing of people in an area. This is a slightly different, and probably much easier, problem. Use an infrared camera If you don't need to count exactly how many persons are in the area, but ...


12

While having so much valuable answers to my question I have also done some further research about the topic. I have found an additional harvesting solution and also a great reference design about a wireless, solar energy powered sensor node, without using a battery. First the additional method from Texas Instruments, which is called RF switch harvesting ...


12

A wet sensor will not measure the same temperature as a dry sensor due to the evaporation of water from its surface and with the required latent heat being supplied by the sensor, i.e. evaporating water lowers the temperature measured. This evaporative cooling of a water-wetted (or ice-covered), ventilated surface is furthermore depending on wind speed thus ...


10

There are a variety of encryption methods you could use to secure your traffic, and each one has a slightly different power usage, so I'm going to pick a couple of popular choices. The methodology I use to evaluate each method should be applicable to any other ciphers you find and wish to compare. AES AES is one of the most popular symmetric-key encryption ...


10

The technical answer to is this security unbreakable? is "no". The primary reason is that biometric attributes are not secrets. Some are easily duplicated, like fingerprints, or images of faces. Some are harder to spoof, like irises. But once a biometric attribute is captured, it can be replayed. And biometric attributes are fixed. If a user's attribute ...


10

Reliable communications between digital devices requires some degree of signal processing to synchronize the data and the timing (clock). Adding relative motion between the transmitter and receiver can complicate the problem. You are probably aware that relative motion can impart Doppler frequency shifts. This also affects the timing of the bit stream. A ...


10

I think it's non-existent today. I work at a Dutch municipality and, though things might have changed now, in December 2017 our environmental department concluded that even semi-professional gas or dust sensors were just not good enough to determine the low levels needed for outdoor measurements. (Including everything Libelium offered at that time for CO, ...


9

I would either go with RS485 or CAN because with long buses a lot of noise can be picked up. These are the most noise resistant as both of them use differential, twisted data lines. RS485 supports distances up to ~1,200 meters with a guaranteed speed of 100 Kb/s. Max 10 Mb/s with smaller distances. It is a multi point bus with up to 32 drivers and 32 ...


9

If possible choose a device that has a built in battery. A few such examples that use the common 2-pin JST connector. The first two are based off of the esp8266 WioLink WioNode C.H.I.P ($9 computer) Raspberry Pi Zero + battery module


9

This is an idea I've had that I'll throw out here... It seems like it should be possible to have a small device that you simply wrap a mains power cord around a few times (or wrap the device around the power cord, I'm not sure which). When the "host" device is powered on and current is flowing, the "parasite" on the power cord would become powered--not much,...


9

As noted by Sean Houlihane in a comment, you're looking for geo-fencing: A geo-fence is a virtual perimeter for a real-world geographic area. [...] The use of a geo-fence is called geo-fencing, and one example of usage involves a location-aware device of a location-based service (LBS) user entering or exiting a geo-fence. This activity could trigger an ...


9

I'd go for OwnTracks (iOS + Android) which lets your phone send GPS-data over (preferably MQTT) the internet. You may set up this to poll your phone and let a server see if the signal is approaching the house which indicates that the phone is traveling in a car or the best would be to have an (old) phone inside the car at all time which only is used as a ...


9

InfluxDB in Domoticz This is a database provided with the Domoticz installation on Raspberry Pi. It allows to use data with time series. Domoticz uses this to modelize sensors' data


8

The bulk of your power will likely be expended on RF transmission, not CPU cycles spent in encryption routines. Every additional bit transmitted will cost you more power than the encryption you're proposing. That means if you take a naive approach, like using AES in CBC mode, you risk increasing the message size to carry the extra bits in each block. If ...


8

Sensor reports to a current thermostat reading feel very private to me. A burglar could use the data to find out when a person is at home. After the house got robbed the owner might decide it's a good idea to sue the manufacturer of the thermostat violating their privacy and thus enabling the burglary. Is this the kind of legal risk a manufacturer of the ...


8

Regarding the humidity and temperature there are the following specifications that should be match: Problems will start above 50 °C and 95 % humidity. But below, it should be fine. The standard detecting conditions are less than the above mentioned values: They have measured the sensitivity characteristic with these conditions (fig 2 in datasheet) so I ...


8

I've not used one of these sensors, but looking at the quoted sensitivity, it would be best placed as close as possible to the source of a leak, or at a low point (many flammable gasses are denser than air, so they tend to collect in depressions at the floor space. You should not be expecting to demonstrate this particular sensor operating, I think. An ...


8

That particular sensor is using RF 345 MHz and is not compatible with SmartThings. To connect the sensor directly to the SmartThings hub it would to be Zwave, Zigbee, or Lan Connected; it would also require a supported device type handler. There are methods of connecting third party alarm sensors to the SmartThings. I don't have any direct experience with ...


8

Radiators should be a source of vibration (driven from the pump), though you would probably need to investigate the resonance frequencies quite carefully. It is also possible to embed kinetic energy harvesting in switches, although that may not be quite the use case you're imagining. The other side of the equation is determining how much energy you require ...


8

WiFi signals Forget about stealing your neighbor's Wi-Fi to surf the internet. Using cheap everyday materials, researchers at Duke University’s Pratt School of Engineering have developed a remarkable device that can convert microwave signals, like those used to wirelessly transmit the internet, into usable electricity. So in the future, you might instead be ...


8

This is a great idea to harvest energy from our daily energy use. But you have to consider that the energy you harvest comes from somewhere. If you want to harvest some heat from your room heating elements, you must be aware that all the heat converted to electricity via your device will not heat the room. So, your room heater will have to consume more ...


8

Building upon several years of deploying outdoor wireless sensor networks, I would like to add the following hint: Think ahead and do not underestimate the problems arising from humidity! I will answer your question by providing some pitfalls with humidity in outdoor devices. However, please consider these general guidelines when planning a wireless sensor ...


8

There are plenty of methods of people counting that could be useful, depending on your exact use case. If you want to measure the amount of people entering an area... you might want to consider an infrared beam counter, which simply detects when the ray is interrupted by something passing through. Here's an example which might be helpful in that case. ...


8

I'll assume that the processing requirements on the device are near enough zero. It sounds like you're using some acceleration input to determine how often to wake up the GSM device. Ideally, you want an MCU which can be triggered from the accelerometer to wake from sleep, and then determine when to send a location ping. Any micro-python based device should ...


8

For Home Assistant specifically, you can connect to the SQLite database and use your own graphing software (or a script) to generate custom graphs. The Home Assistant blog demonstrates the use of Python with matplotlib to do this: # Adapted from the linked code from Home Assistant. import sqlite3 from matplotlib import dates import matplotlib.pyplot as plt ...


8

@jsotola's comment (Something like: "Sounds like something machine learning could do") is probably the right answer, but I'll expand on it a little. It's going to depend on at least the following factors: Size of the room Number of people Type of activity the people are doing Amount of ventilation the room has (windows/ac/...) Accuracy and response time of ...


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