Shelly is not a name that every smart home enthusiast is familiar with in the U.S., but it is a well-established brand in Europe and other parts of the world. Doug Roberson, chief technology officer of Allterco Robotics U.S. provided me with a few Shelly products to test.
Shelly smart home products are manufactured by Allterco Robotics, one of seven companies that make up the holding company Allterco whose headquarters is in Sofia, Bulgaria. Allterco has 20 years of experience in mobile, value-added products and services. The company is expanding beyond the telecommunications industry and is now focusing on the development and distribution of IoT products and solutions.
Allterco Robotics introduced its Shelly line of smart home IoT products in 2018. These products are sold in 120 countries around the world, and the company opened an office in the U.S in 2020.
These include:
Shelly 1: Provides control of a single circuit through its internal relay
Shelly 1PM: Provides control of a single circuit through its internal relay and can measure the power used by lights / appliances connected to the controlled circuit
Shelly 2.5: Provides control of two circuits through its internal relays and can measure the power used by lights / appliances connected to the controlled circuits
Shelly EM: Provides power measurements of up to two circuits by using clamp on current transformers and can control a relay connected to its contactor control terminal. The relay can then control a circuit with any number of lights/appliances connected to it.
All of these are very small, compact IoT devices. In fact, they are each only about the size of two Oreo cookies stacked on top of each other!
The Shelly 1, Shelly 1PM, Shelly 2.5, and Shelly EM all connect through Wi-Fi to an 802.11 b/g/n network and have internal web servers that are used to configure and operate the device using a browser. Each device can also be operated and configured using the following:
- The Shelly smart phone app (Both iOS and Android platforms are supported)
- The Shelly Cloud API
- A local REST API
- MQTT
- CoAP
More information on these APIs and third-party smart home systems that integrate with Shelly devices is provided below.
Beyond just the basic ability to turn on/off a relay and measure power, each device has a number of very useful built-in features
Timers
Auto on and auto off timers can be configured for each relay. The auto-on timer will automatically turn the relay on, whenever it is turned off, after a specified number of seconds. Similarly, the auto off timer will automatically turn the relay off, whenever it is turned on, after a specified number of seconds. This can be very useful if the Shelly 1 PM is employed to monitor the power used by, for example, a refrigerator or freezer. In this case the relay should never be turned off as this would cut power to the appliance. So, it can be programmed to automatically come back on if it was accidentally turned off. Some appliances can be damaged by removing power and immediately powering them on again. In this case being able to delay the relay turning back on is very useful.
Default Power-On Mode
The relay can be configured to turn on when power is restored, turn off when power is restored, or go back to the setting it was at when it lost power. This is very useful if, for example, the Shelly relay is used to control lights in your home.
It would not be desirable to have the lights suddenly come on at 3:00 a.m. after a power outage that began earlier in the evening while the lights were turned on. Alternatively, if the relay was being used to monitor the power of a refrigerator or freezer, the relay should always turn on when the power is restored after an outage.
Scheduler
The built in scheduler allows a relay to be turned on, or off, at a specific time on specified days of the week, sunrise, or sunset. For example, the Shelly relay could be used to turn on outside lighting at sunset each night of the week. The scheduler could then turn the outside lighting off at 10 pm on week nights and off at 11 pm on the weekend.
Security
The feature optionally requires a username/password to control the device.
Time
Connect the device to an SNTP server of your choice so its internal time clock is always accurate and scheduled events will occur when you expect them to. Shelly devices can also automatically detect the proper time zone where they are located. The time zone can also be manually configured if the automatic detection doesn’t properly identify the correct time zone due to how a homeowner’s Internet connection is routed.
Dependability
You can specify a backup Wi-Fi network for the device to connect to in case the primary Wi-Fi network is down.
The Shelly smart phone app also provides the ability to create groups and scenes. Groups allow multiple Shelly devices to be controlled at the same time. Scenes can provide much more sophisticated automation though they do require that the devices be connected to the Shelly cloud.
A Shelly scene begins with defining the “When” condition that will trigger the scene. Scenes can be:
- Repetitively triggered by a timer on a daily or weekly schedule
- Triggered on a one-time basis at a specific date/time
- Triggered when there is predefined activity on another Shelly device
Once the “When” condition is defined, you will need to define the “Do” action that will be performed. There are a number of possible actions:
- Phone notifications (either a push notification or an alarm that will occur whether or not notifications are disabled)
- Email notification
- Adding the event to the Shelly event log
- Send a notification to Alexa (there is a limit of three virtual switches that can be used to trigger Alexa notifications)
- Trigger a Shelly device to turn on or off
Finally, you can define an active time for the scene so it may only be active during specific days of the week and at certain times of the day.
As you can see, Shelly provides a great deal of functionality out of the box without requiring a user to connect their devices to a smart home processor or hub. Provided below is further detail on the Shelly 1, Shelly 1PM, Shelly 2.5, and Shelly EM.
Reviewing the Shelly 1
The Shelly 1 is Allterco Robotics’ most popular product. It is a very small, compact IoT relay switch.
The Shelly 1 is designed to be very flexible. It is the only Shelly relay where the relay provides dry contacts. That is, the internal relay simply connects/disconnects the two terminals on the Shelly 1, and there is no voltage applied to them.
The Shelly 1 can be powered by 12 volts DC, 110 to 240 volts AC, or 24 to 60 volts DC. You simply select the voltage you will use to power the Shelly 1 by moving a jumper between three pins on the unit that are accessed by removing a small rubber cover over an access hole.
By default, the jumper is set for 110 to 240 volts AC and 24 to 60 volts DC operation. The jumper only needs to be moved if the Shelly 1 will be powered using a 12-volt DC power source. The internal relay of the Shelly 1 is rated at 15 amps here is the U.S., which matches the standard circuit breakers used in homes.
There are five screw terminals for attaching wires to the Shelly 1:
- The terminals labeled L (-) and N (+) are used for supplying power to the Shelly 1.
- The terminal labeled SW is used to connect a switch to the Shelly 1. The switch’s other contact needs to be connected to the wire supplying power to the Shelly 1’s L (-) terminal.
- The terminals labeled I and O are connected to the Shelly 1’s internal relay and will be shorted when the relay is closed. These are used to connect the device that will be controlled by the Shelly 1 to it.
- Complete wiring diagrams for the Shelly 1 can be found here.
As described earlier, Allterco Robotics has built a wealth of features into their Shelly relays so they can be used in a wide variety of applications in a smart home. Here are just a few examples:
Basic Lighting Control with Shelly 1
First, a basic lamp can be converted into a smart lamp using the Shelly 1. A wall switch can also be connected to the switch input of a Shelly 1 and the O and I terminals wired to the lighting load to convert the light switch into a smart switch. The “button” input on the Shelly 1 can be configured a number of different ways to provide the optimal user experience. For example, it can be configured as an “Edge Switch” so every change of the switch (on to off or off to on) will result in the Shelly 1 changing the state of its relay.
In this configuration if the switch connected to the Shelly 1 is in the on position and someone uses the Shelly app to turn the connected load off, when the switch is flipped from on to off it will turn the load back on. This avoids user confusion of flipping the connected switch and nothing happening.
Shelly 1 Advanced Lighting Control
The Shelly 1 supports the ability to detach the button input from the control of its internal relay. In this way a Shelly 1 relay can be wired to a lighting load and have the light controlled through the Shelly app, the Shelly 1’s web client, a smart home processor/hub, etc. Then the wall switch (that was previously controlling the light) can be wired to the Shelly 1’s button input and used to control any desired function in a smart home.
For example, in a multi-gang switch box the switches can be configured to control different lighting scenes instead of individual lights that were originally connected to them. If you want to do this, it makes more sense to have the switches being used to select the scenes be momentary switches instead of on / off toggle switches. While I have never personally tried this, there are a few YouTube videos that describe how to convert Decora style wall switches into momentary push button switches. One can be found here.
Garage Door Control with Shelly 1
The O and I terminals that are connected to the Shelly 1’s relay can be connected in parallel with the wall-mounted controller on most overhead garage door openers to make them into smart openers. It should be noted that it is important to provide both audible and visual warnings whenever a garage door is being remotely or automatically closed without a person present to make sure it is safe. For more information on this you can see the article I wrote on making your garage smart here.
Shelly 1 Security Integration
Any standard security sensor that provides a dry contact closure can be connected to the button input on a Shelly 1. Then the Shelly 1 can be integrated with a smart home processor/hub and it can be used to trigger smart home actions based on, for example, the opening/closing of a door or a motion sensor being triggered when someone enters a room.
Similarly, the O and I relay terminals of a Shelly 1 can be connected to a zone input on a traditional security system and trigger the zone when events detected by a smart home processor/hub occur. It is important to remember, however, that a security system goes through extensive testing and certifications to assure that it is 100-percent reliable. Peoples’ lives are dependent on a security system notifying them when an intruder enters their home, if there is a fire, or other critical events taking place in and around the home that the security system is designed to sense. Smart home products are not subject to this same rigor, and this needs to be kept in mind when using smart home technology to augment a security system.
The Shelly 1 and Shelly line of relays/switches are very versatile devices. Their uses in a smart home are only limited by a homeowner’s imagination.
Testing Out the Shelly 1PM
The Shelly 1PM, like the Shelly 1, can switch a single load on/off. However, it differs from the Shelly 1 in several important ways:
- The 1PM doesn’t control a dry contact relay. Instead it switches power from the device’s L terminal to the device’s O terminal on / off.
- It can measure the power being consumed by the device that is being controlled.
- It includes internal temperature protection. The 1PM monitors its own internal temperature and can shut down the device it is controlling if the power being consumed is overheating the Shelly 1PM.
- It includes power overload protection. The 1PM can shut down the device being controlled if its power consumption exceeds a user defined threshold.
- Like the Shelly 1, the Shelly 1PM can be powered by 110 to 240 volts AC or 24 to 60 volts DC. Unlike the Shelly 1 it can’t be powered by 12 volts DC.
There are five screw terminals for attaching wires to the Shelly 1PM:
- The terminals labeled L1 and N are used for supplying power to the Shelly 1PM.
- The terminals labeled SW and L are used to connect a switch to the Shelly 1PM
- The terminals labeled O will supply power to the load when the 1PM is turned on. The second connection to the load must be made to the wire connected to the 1PM’s N terminal. Unfortunately, the terminals on Shelly relays are too small for multiple wires to be connected to them at the same time unless the relays are being used to control low voltage devices that consume very little power.
- Complete wiring diagrams for the 1PM can be found here.
Like the Shelly 1, there is a wide range of ways that the Shelly 1PM can be used.
- Basic and advanced lighting control applications as described for the Shelly 1.
- Because the 1PM doesn’t turn on/off a dry contact relay it cannot be used to control a garage door or interface with a security system as I described for the Shelly 1.
- Making Dumb Appliances Smart – The 1PM can be used to monitor the power usage of a single-phase appliance in a home. For example, the 1PM can be wired into the outlet of a clothes washer. The internal switch would be configured to turn on automatically if power is lost and to turn back on if it is ever turned off. Then the power consumed by the washer during the spin cycle could be studied and a profile created. The profile could look for level of energy usage by the washer’s motor to spin the drum at high speed for a specific period of time during its final spin cycle (vs. the spin cycle that takes place between the wash and rinse cycles). Then when the energy being used drops to near zero (the clothes washer is done) a notification could be sent to the homeowner that it is time to move the load of laundry to the dryer.
- Home Energy Monitoring – The 1PM can be part of an overall plan for managing energy usage in a home.
- Appliance Wear/Failure Monitoring – Some appliances, like a refrigerator will consume more power over time as they show wear, or energy use may spike as the appliance starts to fail. By monitoring energy use of an appliance, a homeowner can be warned when it is time to replace an important appliance, like a refrigerator. If the refrigerator fails, without warning, a homeowner can lose hundreds of dollars of food, adding to the cost of replacement.
Checking Out the Shelly 2.5
The Shelly 2.5 is essentially two Shelly 1PMs stuffed into the same size package. Similar to having two Shelly 1PMs, it can independently switch power to the O1 and O2 terminals on the device on/off. It can independently measure the power being consumed by each device that is being controlled. And, like the 1PM, it includes internal temperature protection. The 2.5 monitors its own internal temperature and can shut down the devices it is controlling if the power being consumed is overheating the 2.5.
Like two 1PMs, it provides independent power overload protection for each device connected to it. The 2.5 can shut down either device being controlled if the device’s power consumption exceeds a user defined threshold.
Like the 1PM, the 2.5 can be powered by 110 to 240 volts AC or 24 to 60 volts DC. Again, unlike the 1PM it can’t be powered by 12 volts DC. The maximum load is 10 amps per channel.
There are seven screw terminals for attaching wires to the 2.5. The terminals labeled L and N are used for supplying power to the 2.5. There are a total of two L terminals on the 2.5. Power need only be applied to one unless the total load of the devices being controlled by the 2.5 is greater than 15 amps.
The terminals labeled SW1 and SW2 are used to connect switches to the 2.5. The Other contact of each switch is connected to the wires supplying power to the 2.5’s L terminals
The terminals labeled O1 and O2 are connected to the 2.5’s internal relays and will have power applied to them when the an internal relay is closed. These are used to connect the loads that will be controlled by the 2.5.
Complete wiring diagrams for the 2.5 can be found here.
Unique Features of the Shelly 2.5
As mentioned previously, the Shelly 2.5 is essentially two 1PMs in one enclosure. However, a feature that is unique to the 2.5 is that it can be configured in the device’s setting to be in “roller shutter mode”.
In roller shutter mode, the 2.5 is used to control a motorized shade or any dual input motor; one input to move the motor in one direction and the other input to move the motor in the other direction. In this case, the O1 terminal of the 2.5 is connected to one motor input and the O2 terminal is connected to the other.
Roller shutter mode then interlocks the O1 and O2 outputs of the 2.5 so that both can’t supply power to the shade motor at the same time. Second, it enables the use of up, down, and stop commands to be accepted by the 2.5. When the up command is sent to the 2.5 the relay feeding the O1 terminal is closed and power is applied to the O1 terminal so it can power the motor to raise the shade. When the down command is sent to the 2.5 the relay feeding the O2 terminal is closed and power is applied to the O2 terminal so it can power the motor to lower the shade. Finally, when the stop command is sent to the 2.5 both relays are opened.
There are also additional settings available when the 2.5 is in roller shutter mode. First, a working time can be set, and the 2.5 will automatically stop all movement after a preset period of time. Second, a cut off power limit can be set. The 2.5 will monitor the power used by the shade motor and will automatically stop all movement if the motor exceeds this limit. A spike in the power being consumed by a motor will typically occur when the device the motor is moving reaches a travel limit or there is an obstruction that blocks the movement of the device.
While the 2.5 can be used to control a motorized shade, there are a wide range of other motorized devices that it could be used control:
- A lift that raises/lowers a TV that is hidden inside a cabinet
- A roller shade that hides a wall mounted TV that is surrounded by a picture frame. The roller shade will have artwork printed on it. The shade will be raised, exposing the TV, when it is turned on. When the TV is turned off the shade will be lowered, hiding the TV, and displaying the artwork in the picture frame.
- Motorized windows and skylights. A smart weather station can detect rain and trigger motorized windows and skylights to close. In addition, the windows and skylights can automatically be closed when either the home’s air conditioning or heat is turned on. If a 2.5 is connected to a motorized window, it is critical to fabricate an interlock that disables the motor from closing the window when the window screen is removed. This keeps the window from accidentally being closed on someone causing injury or death.
Reviewing the Shelly EM
The Shelly EM is a very different device from the Shelly 1, Shelly 1PM, and Shelly 2.5. It provides power measurements of up to two circuits using clamp on current transformers (CTs). Shelly can provide either 120 or 50-amp CTs for power measurement with the EM. The choice of which CTs to use will be based on how much energy the device being monitored will use. For example, if the EM will be used as a whole house energy monitor in a house with 200-amp service, it will require the larger CTs as they will be placed on the “mains” powering the entire home. If EM will just be measuring the power being used by a single appliance, 50-amp CTs should be sufficient.
The EM has a single contactor output. It is only rated for 2 amps and is designed to drive a relay that can then be used to control lights/appliances that draw much more power.
Another difference between the EM and the other devices previously described in this article is that the EM can only be powered by 110 to 240 volts AC. DC power sources are not supported by this device.
The EM, like the 1PM and 2.5, has an internal temperature sensor. However, the latest firmware doesn’t yet support over temperature protection. I’m told that is in the works and should become available with a firmware update in the future.
The EM has independent over-power and under-power thresholds that can be set for each CT. If an over-power threshold is exceeded the Shelly Ems, then the output can automatically be turned off. However, the EM doesn’t have hardware level over-current protection like the 1PM and 2.5.
There are seven screw terminals for attaching wires to the EM:
- The terminals labeled L and N are used for supplying power to the EM.
- The terminals labeled O is the contactor control output and can be connected to a relay that will control power to the device(s) being monitored. The second connection to the relay is made to the wire connected to the to the EM’s N terminal.
- There P1+ and P1- are used to connect a CT to the EM
- There P2+ and P2- are used to connect a second CT to the EM
- Complete wiring diagrams for the EM can be found here
The obvious use for the EM is to measure the power used by one 240 VAC device, or two 120 VAC devices, and then use those measurements as part of an energy management plan. It can also be used in many of the ways that I described for the 1 PM including making a dumb appliance smart. Using the over- and under-power threshold URL actions, messages can be sent to a smart home processor/hub so it can notify a homeowner when, for example, their clothes are done drying and will wrinkle if not removed from the dryer.
Smart Home API Integration for Shelly Products
Allterco Robotics has a fully documented API for the entire product line. Shelly IoT devices have been integrated with the following smart home platforms:
Some of these integrations make use of Shelly devices’ ability to communicate using MQTT. MQTT is an industry standard messaging protocol for IoT device communications.
Drivers for Crestron, Savant, Control4, and RTI smart home platforms are also in the works.
For testing, I wrote a basic Crestron driver that leveraged the local control REST API. The driver I wrote supports on, off, and toggle commands for the Shelly 1, Shelly 1PM, Shelly 2.5, and Shelly EM. It also supports the use of the Shelly 2.5 when it is configured in roller shutter mode to control a motorized shade and reading power measurements from the Shelly 1PM, Shelly 2.5, and Shelly EM.
I expect that the Crestron driver Allterco Robotics is currently involved in developing will be much more full featured. However, until that is ready, the driver I wrote can be found on my GitHub here.
Shelly relays are based on the industry-standard, ESP8266 Wi-Fi microchip. So, in addition to each of the above integrations, Shelly devices include a port that can be used by hobbyists to flash the device with an alternate firmware. One alternative that is popular with smart home hobbyists is the Tasmota open source firmware.
Hands-On with Shelly
The first thing you’ll need to do is to download the Shelly app from either the Apple App Store or the Google Play Store. You’ll need to create an account and provide the typical permissions to send notifications, etc. The app will also need location permissions. This is so it can decide whether to communicate with your devices through either the local or cloud API. You also have the choice of whether to even enable cloud access to your devices. If you disable cloud access you will lose remote access of the devices through the app and the Shelly cloud’s collection of historical power data from its devices.
The first time you use the app, it goes through a loading process. I waited several minutes and then guessed that something might be wrong. I restarted the app, and it then immediately came up and started working. I’ve reported this issue to Allterco Robotics. It isn’t a big deal, but just something to be aware of.
Once the Shelly app was up and running, I added the Shelly 1 that I was testing to the app. I attached a power cable to the Shelly 1 and plugged it in. I then started the app and selected “Add a device.” I was prompted to provide the password to my Wi-Fi network and was then provided with a list of all the different Shelly products. I chose the Shelly 1 and was then prompted to join the Shelly 1’s local network. The app then configured the Shelly 1 and added it to my home network.
The next step was to create a room in the app where you will be installing one, or more, devices. You get to supply the name of the room and a picture. You can either upload your own picture or choose one of the two default pictures available in the app; a living space or a bedroom.
With a room defined you can then add your device to the room. First, you’ll need to supply a name for the device and choose an icon. Each device in a room will have an icon and you can select from 16 choices. You can then choose how the device will be used; as a relay to control some device or to control a light. This doesn’t affect how the device will operate when controlled through the Shelly app or local REST API. However, it does affect how voice assistants and smart home hubs that interact with Shelly devices through the cloud API, will work with the Shelly device. Finally, you can choose which room the device will be located in. You can either choose any room you have created or make it a hidden device that is not exposed within a room for on/off control.
Once your rooms are defined and the Shelly devices added to them, the app makes it very easy to configure or control the devices.
If you happen to be working at a computer, then the web interface for a Shelly device is another very convenient way of configuring and controlling it. However, you just need to be aware that you can only configure or create groups and scenes that were described earlier using the product’s app.
It should be noted that a user will need to periodically check the Shelly app or the web interface for each device they have installed in their home to know that there is a firmware update available. The devices do not automatically download and install firmware updates by themselves.
The small size of the relays makes them very convenient to work with. They are designed to fit inside a single gang electrical box so they can be used to automate the operation of a switch or outlet. It can be a bit of a squeeze when you consider the room taken up by the wires in the box. However, it is no more of a squeeze than when a smart switch or outlet is installed.
Once wired in place, the Shelly devices worked very well. While I encountered a few minor glitches with the app, the devices themselves were 100-percent reliable. I never had a device fail to respond properly to a command or unexpectedly go offline.
Areas for Improvement for Shelly Devices
When you write drivers to integrate with a product, you get a much more detailed picture of it than if you just performed some basic testing. I found the Shelly 1, Shelly 1PM, Shelly 2.5, and Shelly EM to be excellent products. The fact that I have listed a number of areas of improvement shouldn’t be viewed as a critique of the products. It really represents that I saw so much potential in a smart home for the products and just wanted even more.
1) Shelly’s local REST API is a welcome feature that allows the brand’s devices to be directly integrated with a smart home processor/hub such that the devices don’t become dumb when there is an Internet outage. However, there are some holes in the API that need to be filled. Shelly provides URL callbacks so if a device is, for example, controlled through the its app an HTTP call is made from the device to the smart home processor/hub to make it aware of the change in status of the device. This works very well but, unfortunately, there aren’t URL callbacks available for all of the attributes of a device.
Most notable is that there aren’t any URL callbacks to report changes in power consumption by devices connected to a Shelly 1PM or a Shelly 2.5. A smart home processor/hub integrated with these Shelly devices has to constantly poll for power to implement smart home actions such as sending notifications when a clothes washer finishes or to monitor if a refrigerator or freezer suddenly stops operating.
A smart home processor/hub must poll a Shelly 2.5 in roller shutter mode for the position of a shade because there isn’t an URL callback that reports it.
The Shelly Duo bulb (that was not included in this article) doesn’t include any URL callbacks at all so it can’t be seamlessly integrated with a smart home processor/hub without ongoing polling to keep its status up to date.
2) The Shelly 1, Shelly 1PM, Shelly 2.5, and Shelly EM’s internal relay(s) provide normally open contacts. When an “on” command is sent to the Shelly device, it internally powers the relay to close the relay’s contacts which completes the circuit to the device it is connected to.
While relays are very reliable, they are electromechanical devices and will eventually fail. It would be better if there were both normally open and normally closed contacts from the internal relay exposed on each Shelly device’s terminal strip. If, for example, a Shelly 1PM is being used to monitor the power to a refrigerator, then the relay doesn’t need to be continuously powered because the refrigerator could be wired to the Shelly 1PM’s normally closed relay terminal. In this way, even if the Shelly device failed, the refrigerator would continue to receive power and there would be no risk of the stored food spoiling.
3) There are some challenges when using a Shelly EM to monitor the power consumption of devices in a home. Over and under URL actions can be triggered when the power being consumed by a monitored device exceeds or falls below a defined threshold. If the only requirement is to send a notification when, for example, a clothes washer or dryer has finished, then the over and under power URL actions are a good solution. However, there is one thing to understand about the over and under power URL actions on the Shelly EM.
There are independent URL actions for each channel, and they can’t be triggered based on the total power being consumed by a 240 VAC. It would be nice if there were an option to simply add the power of channel 2 to channel 1. Then the existing URL actions for channel 1 could be used to inform a smart home processor/hub of over and under power usage events based on the total power being consumed by a 240 VAC device.
If you do want to use the Shelly EM to trigger notifications when a 240 VAC device, like a clothes dryer, finishes its drying cycle, you may find a workable solution by just monitoring a single leg of the 240 VAC that is being fed to the dryer. If you do this, you will have to see which leg provides a better measure of the operation of the device. On my own dryer the power consumed by one leg periodically dropped to zero while the other leg never dropped below a few hundred watts.
I expect that the one leg was only powering the heating element and when it periodically cycled off the power being consumed dropped to zero. The other leg probably included powering the motor that was constantly running to spin the dryer’s drum and provided a much better indication of whether the dryer was running or not.
4) Most electrical boxes installed today in homes behind switches and outlets are plastic. This is ideal for installing Shelly devices into them as plastic doesn’t attenuate Wi-Fi signal strength by very much. This is not true for a metal circuit breaker panel where a Shelly EM might be installed. If the circuit breaker panel is installed in a basement or garage, it may already be a good distance away from the home’s Wi-Fi router. This will make it very difficult, or impossible, for a Shelly EM to connect to the home’s Wi-Fi network. It would be nice if there were a version of the Shelly EM that included an Ethernet port to work around this situation.
5) While the Shelly 1, Shelly 1PM, Shelly 2.5, and possibly the Shelly EM are designed to be stuffed in small plastic electrical boxes behind a switch or outlet, there are times when that isn’t practical. For example, they might be installed in a large electrical enclosure with DIN rails or a structured media cabinet. In this case, to keep the installation neat and organized, there should be a way of mounting the Shelly devices to a flat surface.
This could be accomplished by either adding some screw tabs to the Shelly cases (that could be quickly trimmed off if not being used) or to include a hole in the case that a screw could go through. Similarly, it would be nice if there were a small flexible cover, like is used to cover the voltage selection port on the Shelly 1, to cover the screw terminals on all the Shelly devices. This would eliminate any chance of someone accidentally touching these terminals and receiving a shock or accidental contact with a non-insulated ground wire inside an electrical box.
6) There is a Wi-Fi status light included on the Shelly 1PM, Shelly 2.5, and Shelly EM. It would be nice if this was also included on the Shelly 1.
7) There should be a notification feature to inform homeowners when a firmware update is available for their devices or an option to automatically install firmware updates. If Shelly devices are integrated with a smart home processor/hub, the homeowner may not ever use the Shelly app or a device’s web interface to become aware of the need to install a firmware update. Firmware updates can include important security patches and not installing these could leave homeowners at risk of their devices being utilized by hackers in an attack.
Shelly Conclusions
Overall, I found the Shelly devices to be very easy to work with, very fast to respond to commands sent using the local REST API, and reliable. Their design makes them very flexible and capable of solving a wide range of problems in a smart home. And, while there were a few glitches when using the Shelly app, the Shelly 1, Shelly 1PM, Shelly 2.5, and Shelly EM all operated faultlessly during my testing.
Their small size makes these devices ideal for installing inside the electrical boxes behind switches and outlets in a home. Alternatively, to turn a lamp bought at a department store into a smart lamp one could be installed inside the base of the lamp. This all makes these devices ideal for creating a smart home where all the technology is hidden from sight and doesn’t take over the home’s décor.
In addition to the uses for these products that I have outlined above, professional smart home integrators may use them in additional ways. Smart home processors, unlike most smart home hubs, are outfitted with relays. These become very valuable resources because if you need more relays than the manufacturer has provided, it can cost hundreds of dollars more to add them. The same is true when a relay is needed at a different location than where the smart home processor is installed. Shelly relays are an ideal solution for this problem at a fraction of the cost.
Besides their use by professional smart home integrators, the Shelly 1, Shelly 1PM, Shelly 2.5, and Shelly EM are primarily products for more advanced smart home hobbyists. Not because they aren’t very useful and of high quality, but simply because they have to be wired into a circuit. You either need to have this level of knowledge or hire someone with the expertise to do it for you; which would significantly add to a homeowner’s cost of using Shelly’s products. Shelly does make a line of plug and play products that the average consumer can install themselves including the Shelly Plug and a line of smart light bulbs. But, the Shelly 1, Shelly 1PM, Shelly 2.5, and Shelly EM all require a level of electrical wiring knowledge to work with that many people don’t have.
