Green Smart House Solution - Max-i Fieldbus

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The Green Smart House Solution
Smart House Systems the Traditional Way
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, but 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. It is also very difficult and expensive to make green sustainable solutions and add even the simplest smart-house features like dimming.
  • You can replace the wall switches with mains dimmers, which reduces the average mains voltage, but there are a lot of disadvantages with this method:
      • Most dimmers can only control one lamp and therefore cannot replace a double switch.
      • There is no or very limited ways to implement more advanced features like multi-way (landing) switching, all-off and remote control.
      • 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 the LED lamps to glow all the time.
  • You can replace the LED-bulb with someone with wireless control such as WiFi, Thread, Bluetooth, Zigbee or Z-Wave, but this too has many disadvantages:
      • Even more electronics is needed in each bulb and with that even more ressources to manufacture, reuse and/or dispose the device.
      • The bulbs need to be powered up permanetly and must therefore not be forgotten in off-state.
      • It may be necessary with routers, border routers, gateways and the use of advanced control devices like smartphones.
      • 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.
      • Wireless communication may be hacked without physical access to the system and 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 needed. The manufacturer must be trusted and must guarantee that all devices are safety updated even several years after the purchase! In practice, this may be impossible - especially with low cost devices.
      • Safe wireless systems like Matter over Thread require a fairly expensive microprocessor with an advanced (128 bit) cryptographic engine and a lot of software layers on top of each other like TCP or UDP, IPv6 (128 bit) addressing, block-chain technology etc. Below the surface most such systems are insanely complicated, which makes it extremely difficult to handle by yourself if you don't have a finished protocol stack, and it may cause a lot of headacke if something don't just works out of the box. 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 ones, who have installed it, it may reduce the selling price of the house!
      • All devices must usually be certified and go through a time-consuming and expensive conformance test.
      • Systems like Matter, which standardize the interoperation on device level, will never be able to cover new, advanced features.
      • It can be very difficult or even impossible to ensure that such systems do not send information about your behaviour to Google and others.
  • You can replace the mains voltage LED-bulbs and with that perhaps also the entire lamp with someone, which is driven by a separate LED driver with remote control such as 0-10V, 1-10V, DALI, KNX or DMX512. This makes it necessary to rebuild the lamp outlets, ensure proper cooling for the LED drivers, which can be very difficult if they must be mounted in insulation material, draw new cables for the control system and add and use more advanced control devices than simple wall switches.

Very often, traditional smart house systems are driven by small batteries or mains voltage, but there are a lot of disadvantages of both methods.
  • Battery powered devices are often chosen because they are easy and cheap to install, but the batteries have a lot of disadvantages:
      • They 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.
      • Battery leakage can cause bad connections and corrosion.
      • Small batteries do not have power enough for example for intelligent and fail safe alarm sensors and for solenoid driven devices like locking pawls.
      • They must be replaced fairly frequently if a device is to be expected to work. This can be difficult for elderly people and it is a very big problem for actuators like radiator thermostats, locking systems and access control because the battery voltage may be high enough for stand-by, but not for operation, so a bad battery or a corroded battery connection may not be detected before it is too late.
  • Mains driven devices including LED bulbs and chargers include an AC-DC converter, which has a lot of disadvantages too:
      • It increases the price and size of the device considerably and may even be a clumsy "brick" on the charging cable as it is usually the case with laptop's and tablets.
      • It generates electrical noise.
      • It may turn off for a short time in case of transients or voltage drops.
      • It may cause a risk of fire and/or shock due to the high mains voltage level and often very doubtful quality and cooling.
      • It require big resources to make and are 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.
      • The necessary conversion to and from mains voltage makes it very expensive to utilize a house hold battery and solar panels to save energy, as an inverter is needed to generate AC. This also significantly reduces the service life and reduces the efficiency at low power level.
      • It often results in a chaos of socket outlets, chargers and cable spaghetti on the floor with very low "Woman Acceptance Factor" - WAF.


A different Sustainable Solution
In 2019, 54 million tons of electronics ended as wast globally and UN estimates that this will grow to 74 million tons in 2030 and 120 million tons in 2050. The best solution to this is simply to avoid most of the electronics, and this is what Max-i makes possible!

The high power capability and use of standard installation cables in a "multi-loop plus two tails" structure as shown on the drawing on the top of this page makes it extremely suited as a supplementary 20-Vdc power supply with control possibilities in the houses of the future. It can replace all the point-to-point connections, most mains voltage converters and chargers and be used to drive and control low to medium-power equipment like for example LED lighting, window openers and sun shading, computers except for high power gaming PC's, tablets and peripherals like screens and modems, low power infotainment systems including TV, low energy refrigerators and freezers, door bells, coupled smoke alarms, burglary alarms and locking systems. In a typical house, such devices use approximately 60 % of the electricity exclusive electric heating, so in case of solar panels, a huge energy saving is possible at a fraction of the cost of a traditional AC system, which is also designed for driving all the high-power devices like stoves, ovens and other kitchen appliances, washers and dryers, vakuum cleaners etc. With Max-i, high power devices are still driven by the mains voltage. Calculations done by the Danish engineering company Rambøll shows that such a low-voltage DC-network can save the Danish households in the order of 1 billion Danish kroner per year corresponding to approximately 134,000,000 Euro or $144,000,000.

There are two primary reasons to chose 20 V instead of the much more common 24 V or 28 V.
  • Since the minimum burning voltage of an electrical arc is 18 - 20 V (between copper parts), it is the highest voltage, which cannot cause a dangerous arc. At just 28 V, which is the charging voltage of a 24-V battery, arc lengths up to 12 mm are possible at 50 A and house hold batteries can easily source way over 1 kA! At 20 V, a creepage distance of only 1 mm is enough to extinguish an arc and a bigger distance is not reasonable to specify.
  • It has become the de facto standard for the maximum level for many chargers for mobile phones, tablets and laptop computers as listed below:
      • USB Power Delivery (USB-PD) up to version 3.0 (20 V, 5 A = 100 W). Version 3.1 however goes up to 48 V, 5 A = 240 W.
      • Quick Charge from Qualcomm (20 V, 5 A = 100 W).
      • SUPERVOOC Endurance Edition (20 V, 7.5 A = 150 W).
      • Infinix (20 V, 8 A = 160 W).
      • Xiaomi HyperCharge (20 V, 10 A = 200 W).
      • Realme (20 V, 12 A = 240 W).
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. 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.

Max-i is also the ideal replacement for the traditional 12-V systems in mountain huts without any grid connection as the higher voltage is better suited for LED lighting and can be used to charge and drive laptop PC's directly. 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.

Max-i can be installed and serviced by any electrician and like most other hardware standards like CAN, it does not get obsolete overnight. For smart house applications where there is no problems with mutual coupling to other cables and high current levels are needed, Max-i uses a 5-conductor industrial flat cable with two conductors (1 and 5) for positive voltage (L+), two (3 and 4) for negative voltage (L-) and one (2) for communication (COM), and it uses piercing technic to get contact and make outlets without cutting the cable. If more power is needed than possible with a pure 20-V system, conductor 4 and 5 may instead be used for mains voltage (mains-plus-dimming) as shown below:

Security, Privacy and Safety
Security is of the utmost importance to many people, but it is an area where present technology based on wireless communication and small batteries is almost useless:

  • If an alarm system should not give you false security, it must be fail-safe, that is, an alarm is also generated in the absence of a sensor signal - not just as an active signal. If a wire is cut or the system is jammed, an alarm must be generated in less than 1 second, but due to the battery life, it is usually not possible to supervise a device more frequently than approximately once every 10 minutes.
  • Battery driven systems only have enough power for simple, low-power sensors such as passive infrared detectors (PID), but these kind of sensors generate many false alarms and may be easy to fool.
  • Wireless communication is very easy to jam and may generate false alarms due to other wireless communication in the same frequency band. False alarms and jamming are not only very irritating, but also makes you nervous and it can even be used to force you to switch the system off. A thief just needs to jam the system from time to time in the night to trigger it until you are forced to switch it off because the alarm wakes-up your neighbors.
  • It can be very difficult to ensure that wireless communication do not disclose information about your home. This is especially a problem with alarm systems with cameras where it is almost imposible to guarantee that your behaviour is never transmitted to third parties or to second parties such as alarm centers when you don't want it. If you even add a cloud based speech recognition system, your privacy is gone forever. Everything you say or do may end up on the wrong places on the internet, and even though it only ought to be the commands to a speech recognition system, which are transmitted, there are people listening to optimize the systems!
  • Wireless connection may be used to hack into the system even from a long distance. The safety is not better than the weakest link and the majority of devices are not updated after some time or not at all. Just one unsafe device is enough to open a backdoor into your system on the wrong side of the firewall where there is free access to your other devices and computers.

With Max-i, it is different.

  • It has power enough for even the most advanced and fail safe sensors and for driving locking pawls by means of solenoids. Battery powered locks need to use motors, which are slow, need protection against blocking and may even run out of power.
  • It is fast and powerful enough to destroy the night vision of a thief by means of powerful light flashes.
  • Unlike a wireless system, a hardwired system like Max-i is not accessible from outside (unless a gateway/border-router is added), so it is not necessary with advanced encryption standards etc., which makes the necessary electronics much simpler, cheaper and smaller and increases the efficiency a lot.
  • It cannot be jammed unless you get physical access to the cable or an outlet with enabled communication, which should only be possible from alarm monitored areas.
  • The Max-i controller (chip) is entirely hardware based and therefore cannot be reprogrammed to anything else than its dedicated purpose so there are no "mousejack" problems etc.
  • It is very easy to log all communication to ensure that nothing or nobody transmit unwanted information behind your back. The Max-i controller even has a fairly advanced acceptance filter, which can block telegrams, which would otherwise overload the log-system.
  • Unlike for example WiFi, there is virtually no limitations on how many devices you can connect without any noticeable degrade of performance.
  • In daily use, you don't need an internet connection, which keeps even the best hacker out. Even when you need it, the connection only goes through one device, which is much easier to keep safety updated.
  • It can easily be installed by the user himself just by connecting the sensors to a free outlet, and polling or heartbeat can then ensure that the alarm is triggered, if a sensor is disconnected.
  • There is virtually no electromagnetic fields - not even from 50 Hz or 60 Hz solar power inverters.

Simplicy by Design
Unlike most other smart-house (and fieldbus) systems, Max-i is extremely simple. For example. the publisher-subscriber method, which addresses the various process values instead of the devices, makes it unnecessary to specify a lot of device data models, which anyway almost always will be more or less outdated. Even the most complex device now and in the future just publish and consume a number of process values, so it is only necessary to specify a few standard data types. With the long 31-bit data identifier, only 9 bytes are needed to set for example the hue and smoothing time of a tunable white lamp and this includes a 20-bit CRC check to detect errors and a 7-bit Hamming code on the identifier to protect against masquerading. As a comparison, the following table shows what Matter over Thread uses for the same job:

Matter over Thread
802.15.4 PHY Header
Preamble Sequence

Frame Length
MAC Header
7 - 37
Frame Control

Sequence Number

Address Information4 - 20
Auxiliary Security Header0 - 14
MAC Payload
28 or 33
Any Mesh Header for Multihop0 or 5
6LoWPAN Header

ICMPv6 Header

Data Payload Layers
Maximum 73 or 78
Message Framing and Routing
Security Encryption and Signing
Action Framing
Interaction Model
   Interaction 1 with another Data Model
       Transaction 1
           Action 1
           Action 2
       Transaction 2
           Action 1
           Action 2
           Action 3
   Interaction 2 with another Data Model
       Transaction 1
           Action 1
           Action 2
           Action 3
       Transaction 2
           Action 1
           Action 2
Device Data Model
       Node n
           Endpoint 0
               Cluster: Descriptor server
                   DeviceTypeList server
               Cluster: BasicInformation server
                   VendorName attribute (16 bit)
                   ProductName attribute (16 bit)
                   Startup event
               Cluster: GeneralCommissioning
           Endpoint n - Dimmable Light
               Cluster: OnOff server
                   OnOff attribute
                   OnTime attribute
                   Toggle command
               Cluster: LevelControl server
                   CurrentLevel attribute
                   MoveToLevel command
                   MoveWithOnOff command
Application layer
Frame Check

Not only is the data model fairly 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.

Even though Max-i is very simple - especially compared to this, it is much more powerful. On a 200-m line, it only takes an average of 454 μs to send the message to the lamp, which may be up to hundreds of times faster than Matter over Thread and is thousands of times faster than Bluetooth LE, and Max-i is even faster if the ability to transmit data to more lamps in the same telegram is utilized. In that case, it can be used for professional stage light with a performance far, far above what is possible with Matter, Philips Hue, DALI, KNX or any other smart house system today.

Simplicity in use
Max-i may be operated any way you want. Even without a central controller, you may for example control lamps, window openers etc. by means of traditional wall mounted buttons, which is usually the most convenient. In the long run, almost no one bothers to find the right app on a mobile phone every time they just want to turn a lamp on or off. The only difference you will experience with Max-i compared to a traditional system is perhaps a more beautiful touch control with light indication and that you simultaneously get a light dimmer in all lamps with a lot of features like night light and programmable start level, automatic daylight control, all-off (and all-on), synchronized multi-way landing switching and possibility for emergency light with programmable color (need to be reddish in case of smoke). If you connect the bus to a WiFi or Bluetooth interface, you may do the same from mobile phones and tablet and this also makes it possible to set different scenes and control the color hue in case of multi-color lamps. Max-i may of course also be connected to controllers and computers, which can enable more advanced functions like energy management and making the home looks inhabited when you are not at home. It is even possible for an advanced TV to control the light in real time from the image lighting with the same speed and performance as professional stage light.

"Everything should be made as simple as possible, but not simpler."
Albert Einstein

"Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away."
   Antoine de Saint-Exupéry.

.This page is created with WebSite X5 and updated April 5th 2023
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