Green Smart House Solution - Max-i Fieldbus

For many years, lighting in buildings has been implemented with simple point-to-point connections between wall switches and lamp outlets in the ceiling. This is easy to overlook and install by any electriciant, which is very important, but it it has a lot of disadvantages:

• All the point-to-point connections make it impossible just to use flat cables and connect everything by means of piercing technique.
• A failure on the neutral conductor, which is often routed through several contacts and outlets, may cause the voltage to raise from 230 Vac to 400 Vac if another phase is heavily loaded, which may destroy a lot of equipment and even cause fire.
• It is very difficult to rebuild - especially in low energy houses with an unbroken vapor barrier between outer walls where it may be necessary to remove the ceiling.
• There is no or very limited ways to implement more advanced features like multi-way (landing) switching, all-off and smart-house features.
  
• Most dimmers can only control one lamp and therefore cannot replace a double switch.
  
• Because most LED-drivers and LED-bulbs have a capacitive input, the dimmer needs to be a trailing-edge type, which is much more expencive than a simple leading-edge TRIAC dimmer.
  
• There may be a minimum wattage, with can be difficult to fulfill with LED lamps and may require a resistor, which burns off energy all the time.
  
• The flicker-free dimming range is usually very limited - often to only 10 %, which the eye only regards as a 2.7 times reduction in light intensity.
  
• Induced currents may get LED lamps to glow all the time.
  

Distributed I/O

This is a more advanced version where groups of control modules in one or more control cabinets are linked together by means of a fieldbus so that some cabling can be spared. Each control cabinet contains one or more modules for example for:

• Power supply.
  
• Central controller.
  
• On/off, open/close or "american" 3- or 4-level switching.
  
• Direct lamp dimming by means of 230 Vac or 115 Vac leading edge or trailing edge outputs.
  
• Indirect lamp dimming by means of control signals to other devices like for example 0-10 V, 1-10 V or a fieldbus like Dupline, DALI or KNX.
  
• Boolean (digital) on/off or multistate sensors.
  
• Analog sensors and inputs for example for energy, temperature, water, humidity, fire, smoke, air quality, 4-20 mA etc.

There are however still a lot of serious disadvantages:

• It is a very expensive and physical big solution because it requires one or more cabinets and a lot of different and often expensive modules.
• It is impossible to add new features before a module for that functionality is available.
• Although some cabling is spared, there is still a point-to-point connection from each modules to the connected device(s).
• It is usually necessary to draw new cables if the system is expanded or rebuild.
  
• The limited number of modules in each cabinet may make it impossible to expand, or it may be necessary to mount a new cabinet, which may be difficult to find space for.
  
• The used fieldbus usually does not have enough power to drive actuators, lamps and sensors directly so it is usually necessary with a power supply - either through the modules like switching and direct dimming or to the devices themselves. This may make it necessary with further cabling and maybe a galvanic separation between fieldbus and power supply to prevent ground loops.
• The fieldbus is often proprietary so that it is impossible to use modules from different vendors. This may make it impossble to expand and/or repair the system.

The new Trend

To work aound the limitations of these methods, by far the majority of all smart-house systems today use wireless communication, battery driven contacts and sensors, battery or mains driven actuators and mains driven lamps. This is very easy and fast to install even in existing houses where it is very difficult or almost impossible to draw new cables, but it's like peeing in your pants to keep warm. After the initial advantage, it is just an endless row of serious disadvantages:

Wireless connunication

• Wireless communication may be disturbed by other communication in the same band and may be jammed so that for example alarm systems either don't work or create false alarms with perhaps a loud siren sound in the middle of the night, which a thief may utilize to force the owner to switch it off.
  
• Wireless communication may be hacked, and WiFi based systems may even open a back door into your computer network on the wrong side of the firewall so a very high degree of safety and credibility is necessary. All manufacturers of devices on the network must be trusted and must guarantee that their devices are safety updated even several years after the purchase! In practice, this is usually impossible!
  
• It is extremely difficult to log and decode the activity so it is virtually impossible to ensure that wireless systems do not send unwanted information about your behaviour or even pictures to hackers, Google, alarm companies and dubious websites.
• It is usually necessary with routers, gateways etc., and if something don't just work out of the box, you may be in serious trouble and often on your own.
• Safe wireless systems like Matter over Thread require a fairly expensive microprocessor with an advanced (128 bit) cryptographic engine and a lot of extremely complicated software layers on top of each other, and the devices must be certified and go through a very time-consuming and expensive conformance test. This makes the devices very expensive and difficult to make - especially for small companies, who wish to enter the smart-house market. From August 1^st 2025, similar security requirements will apply to all wireless devices sold in Europe as they must comply with the RED DA radio directive where cyber security is built in so that they cannot harm other connected devices and applications and at the same time guarantee personal data privacy in connection with the communication. It is expected that there will also be requirements for patch management, where in the future companies must be able to proactively deliver software updates to patch security holes. This means that even low-cost devices from China must be allowed Internet access, increasing the risk of malware considerably.
• Systems like Matter, which standardize the interoperation on device and function level, are very much like standard Windows drivers - they can handle the most basic functions, but will never be able to keep up with new, advanced features.
• Complicated standards change very fast and may make older systems obsolete. There are numerous examples of smart-house systems, which cannot be expanded or rebuild after just a few years, and that newer products from the same manufacturer are not even backward compatible! If a smart house system cannot easily be serviced, safety updated, rebuild and expanded for a very long period af time and not just by the one, who has installed it, it can reduce the value of the house!

Battery driven devices

• Batteries require many resources to make and recycly. For example, it requires approximately 270 Wh to produce a single AA alkaline battery, but the stored energy is only approximately 3.9 Wh, which is 70 times less, so battery-driven devices are very far from being green if they are not rechargeable.
• Small batteries do not have enough power for example for solenoid driven devices like locking pawls and for intelligent and fail safe alarm sensors and especially not for sensors based on AI (Artificial Intelligence). In the future, AI will enable many unprecedented possibilities such as facial recognition, alarm sensors that can distinguish between humans and animals, fall detection of elderly people, etc., but the downside is a very high power consumption, which excludes systems based on battery-powered devices from keeping up with the technical development.
• There may not be power enough to supervise an alarm sensor more frequently than typical once every 10 minutes, which delays any tamper detection.
• The batteries must be replaced fairly frequently if a device is to be expected to work. In a typical Bluetooth or WiFi contact, the batteries only last for 2 - 5 years depending on the use and in door locks, it is typical only 1 year. If you choose a battery driven solution, you will be facing an endless battery replacement for years to come, which is certainly not very green and can even be very difficult for elderly people.
• The low battery voltage of typical 3 V is far too low to burn through corroded contacts, which requires a fritting voltage of approximately 100 V/µm, so the usual click contacts may work fine on new devices, but after a few years, you may experience that you have to push the buttons hard many times to make them work or they don't work at all and these problems only get worse.
• Battery leakage and moisture very often cause bad connections and corrosion and together with the short service life it is a very big problem for actuators like radiator thermostats, locking systems and access control. The battery voltage may be high enough for stand-by, but not for operation, so a bad battery or a corroded connection may not be detected before it is too late and you may stand outside your house in rain or snow with no way to enter unless you have a powerbank to power the lock.

Mains driven devices

• The devices need to be powered up permanetly and must therefore not be forgotten in off-state. This is especially a problem if a device is driven from an outlet in the ceiling or on a wall.
• It is not possible to drive the devices directly from a house hold battery. This makes it very expensive to utilize solar panels to save energy.
• The necessary AC-DC converter increases the price and size of the devices considerably and may even be a clumsy "brick" on the cable.
  
• It may cause a risk of fire and/or shock due to the high mains voltage and often very doubtful quality and cooling.
  
• It generates electrical noise.
  

• It may turn off for a short time in case of transients or voltage drops.
  
• It require big resources to make and is difficult to recycle due the the use of toxic epoxy boards and big components with the result that the device often just end up as waste in the incinerator or even on the landfill.
  
• It limits the service life of the device considerably - typical to less than half, which makes the waste problem even bigger.
  
• It often results in a chaos of socket outlets, chargers and cable spaghetti on the floor with very low "Woman Acceptance Factor" - WAF.
  

 

The 100 W of both USB-PD 3.0 and Quick Charge is due to the safety standard IEC 60950-1, which specifies a maximum power of 100 W and a maximum current of 8 A. In this way, "the maximum apparent power and fault current available on the outlet under any load conditions including a short-circuit are limited to magnitudes not likely to cause ignition under fault conditions in connected equipment mounted on, and constructed from, suitably rated materials." Higher power and current levels should be used with great care - especially if a USB-C connector is used as a standard USB-C connector and cable can only handle 5 A continuously!

Since the charging voltage of a 20-V battery fits very well with the maximum-power-voltage of 54-cell solar panels depending on the voltage variations of the battery, such panels may be connected directly by means of a simple Max-i controlled switch as shown on the drawing. This saves the traditional charging controller. The charging voltage is simply set by connecting an appropriate number of solar panels, which changes the charging current in steps of typical 20 - 180 W depending on the sun light. This corresponds to micro inverters, but at a fraction of the costs. Even in case of a failure on the battery connection, the load dump transient, which occurs until the panes are disconnected, is limited to approximately 35 V (open circuit voltage of the panels), so there is never any shock hazard, which is especially important in case of fire extinguishing by means og water, which may be very dangerous on traditional high-voltage systems.

In sunny areas, it may be possible to drive the devices totally off-grid even in the winter, and the excess power in the summer may then for example be used to drive a ventilation heat pump and additional 24-V heating elements so that the house gets ventilated and additional heating is not needed most of the year, which can save a lot of energy. The outlet of cold, dry air from the heat pump can even be used for a (supplementary) compressor-less refrigerator to squeeze the last efficiency out of the system and make the household even less vulnerable in crisis situations. As the global temperature is rising (AGW) this is especially important in areas, which are often hit by hurricanes, but the war in Ukraine has also shown that the first thing an enemy will do is to destroy the power infrastructure. Without electricity, the citizens has no light, no communication, no heating, no water and after just one week, any food in freezers and refrigerators may be destroyed so they may even starve. The ability to run off-grid (islanding) with the most important parts will therefore become more and more important in the future and with Max-i, it is possible to realize this at a very affordable price and without any shock hazard in case of floods or damages, which must be repaired.

Even though many traditional photovoltaic systems have batteries, they generate AC for the grid and must therefore have "Grid - Anti-islanding" to prevent that a disconnected grid is powered up and therefore becomes dangerous to the utility workers, so the majority of these cannot run off-grid, and the few ones, which can, are very expensive. With traditional systems, you may find yourself without electricity even though you have the roof full of solar panels.

Max-i is also the ideal replacement for the traditional 12-V systems in mountain huts, hunting lodges and holiday cottages without any grid connection. The higher voltage is better suited for LED lighting and can be used to charge and drive mobile phones and laptop PC's directly, and the inherent possibility for light dimming makes it possible for a household battery to last much longer in periods without sun and wind such as high pressure weather in winter. Because of the logarithmic characteristic of the eye, the power consumption is reduced to only 18 % if the light is just dimmed to what the eye regards as half. Besides, the multi-drop line is easier to install in a nice way than point-to-point connections between buttons and lamps.

If there is not enough solar power to supply the system in the winter, a grid-powered charger may be necessary as a supplement, but it can be quite small and thus inexpensive as it should only be able to deliver the average power. Besides, it can charge the battery when the grid is low-loaded and/or the share of renewable energy is high and thus both save money and CO2 emissions. Of cause it is also possible to add a 230 Vac or 115 Vac inverter directly to the battery and in this way sell excess electricity to the power grid and/or install high voltage outlets, which may be used to drive equipment, which cannot be driven from 20 Vdc. The inverter must however be switched off in periods where it is not needed (loaded) as it would otherwise drain the battery.

Not only is the data model and the underlying layers extremely complex, but before two devices are able to talk to each other, it is even necessary to build an encrypted communication channel (interaction relationship) between them, so unlike Max-i, devices including debuggers cannot just be added and removed "on the fly" at any time.