Enocean: Energy Harvesting Switches and Sensors

switches or sensors without wires no problem if you use batteries but without batteries the innotion alliance created a standard for such devices so let's have a closer look at switches or sensors that do not need a battery change and here i have a cheaper chinese clone how does it compare and how do these devices compare with sigbi or ble switches and sensors a lot of questions gritsy youtubers here is the guy with the swiss accent with a new episode and fresh ideas around sensors and microcontrollers remember if you subscribe you will always sit in the first row wires to switches or sensors in our homes are expensive and if you rent your home even not possible adding one or moving it to a different place in an existing home is a nightmare this is where the enocean devices come into play they are increasingly used in modern buildings a good reason to look at them the technology is not new it was invented in 2001 by a siemens spin-off company in germany in 2008 the innocent alliance was founded and in 2012 it became an iso standard this is good news for all interested in this technology because it is here to stay and has been adopted by different companies but how does it work all in ocean switches or sensors consist of a transmitter on either 868 902 or 920 megahertz ism band we know these frequencies from our lora devices and know which one belongs to which geography nothing special what is noteworthy is that they are coupled with an energy harvesting part so they do not need external recharging or battery changes and this is the deciding factor for buildings the closest competitors are zigbee or ble sensors or switches both are low power but both usually are battery operated even if batteries live for a long time you still have to replace them from time to time and this creates maintenance costs for buildings you even need some sort of preventive battery management because if a critical switch suddenly does no more work because its battery is exhausted it's not fun my harley for example expects this vle dongle in my pocket the engine will not start if its coin cell is flat a comfortable theft protection because a harley without a running engine is a lot of iron to carry away unfortunately the flat battery always happens if you are on a trip with friends you see the difference between battery operated and autonomous is huge for many applications here i have a few enotion devices this switch is suitable to operate two appliances for example it is not cheap but also not too expensive compared with other commercial switches for homes you can mount it directly into a wall as every other standard switch its operation definitely needs more force than an ordinary switch because with your button press you have to create enough energy to transmit a message how can we use it in our automation systems in addition to the transmitter we need a receiver that can be connected to our existing installation fortunately we get two raspberry pi compatible receivers one can be attached to the expansion header of the raspberry and the other is a usb dongle there are two reasons i would go for the usb dongle firstly i do not like anything which blocks the space above the mpu of a raspberry pi 4 because it complicates cooling and secondly i like to place any radio receivers at a distance to digital devices like raspberries because they create some noise that as we will later see quickly reduces a receiver's reach i rather like to add a short usb cable and place the receiver a few centimeters away from the pi as i did with this zigbee receiver now we have a transmitter and a receiver so what do we need next we need a way to decode signals and translate them into commands for automation because an ocean has its roots in germany the platform fh em with the same roots offers a good integration you also find integrations for home automation as well as into node red because i still use node red i will show you this integration i tried fhem and it worked more or less the same way and the first steps are precisely the same first we insert the usb receiver into the raspberry because it uses a serial protocol we have to disable the console with this command then we delete this text and save the file with ctrl x and y now you can check if your dongle is recognized after typing lsusb you should see this line and with this command this line this is the device we will get the telegrams from the n ocean sensors and switches now everything is okay and we can go to node red and install the emotion palette and this example flow you find the link in the description make sure you uncomment these lines in the settings.js file of node red otherwise node-red will not save the ids of your devices and add this line to the docker compose yaml file if you run node red in a docker container like iot stack shown in video number 352 otherwise node-red will not see the usb receiver now we can start to pair my manual switch my reed switch and my temperature sensor the latter two work with solar power in reality they do not need the sun to work they also work inside a building if there is some light available the switch works without solar energy first we inject a learn command and press the switch then if we check the actor node we see the switch with its unique number next we inject a next learn command and press the learn button of the read switch sensor and the same procedure with the temperature sensor now all three sensors are known to node red and we can integrate them into our flows two additions are essential first you can encrypt the messages if you want i did not try it because the temperature in my lab is not secret and second an ocean recently introduced ple sensors i did not find a lot of information about it and if they support meshes otherwise the range is probably shorter mainly if there is no line of sight between the sensor and the receiver now we have one thing left the energy harvesting part let's start with the switches they work with the energy provided by the fingerprints here is the part which generates energy when pressed it consists of a coil and a magnet as with all generators electrical energy is created if a magnet moves in relation to the coil because the speed of movement is important a mechanical construction with two states is included the mechanism uses a loaded spring to accelerate the movement and create as much energy as possible let's have a look at the voltage coming out of the coil depending on the direction of the movement it creates such a mountain with a peak voltage of 10 to 15 volts utterly useless for a transceiver ic which needs a positive 3.3 volt or less so we need circuitry to convert the energy into a usable form the easiest way to do that is to add a full bridge rectifier now we only have positive peaks if we add a capacitor we can store the energy a 100 microfarad capacitor creates this curve after a press consisting of a forward and back movement we see around 2 volts so we need a boost converter to create a stable 3.3 volts i happen to have an ltc 3588 energy harvester module in my drawer which is precisely for that purpose it even has a built-in rectifier and a capacitor we only need to connect our coil to its input pins and select the output voltage and really we get an output voltage of 3.3 volts but only if we move the switch a few times and the oscilloscope probe discharges the capacitor quite fast so you see the enocean crew did a marvelous job in harvesting this small energy and creating a reliable radio signal out of each button press i would not try it myself the other two sensors work with tiny solar cells which deliver 5 microamperes at only 200 lux why 200 lux a typical pc workplace offers 200 to 500 lux a conference room usually a bit more and a corridor still delivers 50 to 100 lux as we see here the read switch sensor consumes 100 milliampere seconds for one transmission so we need energy storage between the boost converter and the transmitter both sensors use an ms412 fr lithium battery with a nominal voltage of only three volts and a small capacity of one milliamp per hour they seem to be sensitive to heat and have to be hand soldered by the way the time it takes to charge this small battery is 27 days with 8 hours of indoor light it can transmit 10 times per day so you see energy harvesting works on a much lower level than the esp deep sleep where we usually are happy if we get down to the 10 microampere range also here they use very low power components i also found a cheaper chinese alternative to the switch which works with a simpler mechanical design it uses a piezo element instead of a magnet and a coil its pricing force is smaller the energy harvesting circuit also consists of a rectifier and a capacitor but no boost converter and they use a cmt 2119a transmitter chip i leave you a link to a video of big clive where he explains the circuit in detail unfortunately he did not do any analysis of the radio signals so let's check them out and compare them with the ones created by the emotion system here we see the signal of the cheap button on 433 megahertz as expected it is very short because the energy harvesting is simple and for sure will not yield a lot of energy however from time to time it emits a very wide signal which for sure does not comply with regulations maybe it is caused by a too low voltage the 868 megahertz signal of the n-ocean is much more robust and longer it also is clean which definitely gets better coverage as well as a more reliable connection i can show you also the effect of a raspberry pi on the signal of the receiver if i place its antenna close to my raspberry the noise floor increases a lot and you hardly see the signals the so called signal signal-to-noise ratio is reduced and with it also the range both devices use like our lordanod's so-called alloa protocols this means that the sensor transmits its message and hopes that the receiver gets it if not the message is lost this is not a massive problem for light switches because we can press the button a second time if the first is unsuccessful and the room stays dark however for a window alarm against burglars this is probably more severe i doubt that a burglar will close and reopen the window if it does not hear the alarm sound the 868 megahertz band is probably better suited than the 433.92 megahertz channel used by many other sensors it is wider and has more channels all in all in ocean is an exciting technology standard for building automation because it saves money and allows to place switches and sensors without wires no batteries are an essential feature for buildings with hundreds of sensors and switches but is it worth the extra charge for home automation i think no because we build and operate our own systems it is easy to replace batteries from time to time at an extremely low cost because we do not charge our hours one advantage could be that the innocent devices are compatible with the mechanical dimensions of standard switches used in homes and probably look better to a lay woman if you know what i mean this sick beat button would be hard to integrate and look good maybe the price difference in this case is less critical because it is a one-time investment would i use the cheap chinese button no for sure not it is not very reliable in addition it is ugly but it was interesting for me to see that we will get more and more low power components that can be used with relatively simple energy harvesting maybe we will see more zigbee and ble components without batteries in the future i think this would be a good combination because other than an ocean these technologies can build meshes to extend range that was all for today as always you find all the relevant links in the description i hope this video was useful or at least interesting for you if true please consider supporting the channel to secure its future existence thank you bye

Channel: Andreas Spiess

Views: 51,090

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Id: ydNg0nbUJeQ

Length: 14min 58sec (898 seconds)

Published: Sun Oct 31 2021