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This page is updated February 13th 2020. It is only available in English.

  Max-i Association
c/o Innovatic
Bøgebakken 3, Gjessø
DK-8600 Silkeborg
Phone:  (+45) 86 84 72 92



Welcome to the official home page for the Max-i fieldbus
and Max-i Association.

Specification v10.2 has been released!

Battery voltage changed from 18 V ±20 % to 20 V ±23 % to:

  • Be able to comply with the voltage range of USB Power Delivery and Quick Charge (20 V ±5 %)
    when the battery is not charged and in this way be able to the utilize solar power much better.
  • To be able to use devices designed for standard 24-V operation (up to 24.6 V).



Max-i is a new, very cheap, but extremely powerful fieldbus, which enables the lowest, total, automation and LED-lighting costs ever seen combined with maximum performance! It may be regarded as a combination between a highly improved CAN bus and a 20-V power supply and may be used for virtually all low to medium speed applications (up to 30,000 telegrams per second) like:

  • Industrial, building and home automation including motion control and safety applications.
  • Transportation applications such as automotive, special vehicles, railway, ships and aerospace.
  • Traffic lights and supervision on bridges and tunnels.
  • Intelligent LED lighting including demanding stage light and architectural lighting.
  • Supplementary 20-V supply with control possibilities in the houses of the future.
  • Internet of Things - IoT.
  • Military applications.

Max-i has six basic properties:

  • It is possible to make a complete bus interface in one integrated circuit (IC), which is small and cheap enough to be built into even the smallest and most price sensitive actuator, sensor or lamp, gets its supply voltage of 20 V (15.4 - 24.6 V) directly from the bus and only needs an absolute minimum amount of external components - often only 4 capacitors including capacitors for a 5 V and a 3.3 V outputs (100 mA switched-capacitor converter), which may be used for driving external circuitry. This enables a whole new world of single-chip sensors and IoT devices and it not only saves the traditional distributed coupling boxes, components for transient protection and a lot of cabling, but also the expensive and time consuming conformance tests, which are required by most other fieldbus standards. It also makes it possible to do with only one bus in automotive applications because Max-i is almost as cheap as LIN, more powerful than CAN, as deterministic as TTCAN (Time Triggered CAN) and for a given amount of money, it offers the same speed and safety as FlexRay.

  • It is possible to use cheap, standard, unshielded and un-terminated installation cables instead of special communication cables. This not only saves a lot of money and mounting troubles, but also makes it possible to transfer much more power over the bus than any other fieldbus. If more power supplies are used or the cable is bend together in a "multi-loop plus two tails" topology as shown below so that all segments except for the two tails receive power from both sides, up to approximately 800 W per segment is possible on 4 x 4 mm2 (balanced) cables and even 1500 W on 5 x 4mm2 flat cables where two conductors are used for the positive supply (L+), two for the negative (L-) and one for communication, so in practice an almost unlimited amount of power is possible.

    The principle may be expanded to any number of loops for example in case of buildings with more floors. Since there are two cables in parallel in the worst-case points, the DC-resistance is reduced to the half and with that the voltage drop.

    With a 5-conductor flat cable it is even possible to mix Max-i with 230 Vac or 115 Vac mains voltage for example to control lighting, window openers and sun shielding in big buildings.

    Because the cable is not shielded, the traditional dilemma with the shield connection is avoided. For the sake of noise immunity, a shield must be connected to ground/chassis in both ends, but it is simultaneously a very bad idea to establish ground loops and potential equalization between different parts of the plant through a thin fieldbus cable - especially in plants, which use a TN-C net with a common neutral and protective earth! Nevertheless, it is common practice with most other fieldbus systems!

    The name Max-i means Multiple Access Cross (X) coupled interface. It refers to Max-i being a multi-master bus (no dedicated master and slave units), which for industrial applications, railway applications, stage light control and long distance communication uses a cable with 4 conductors connected as a balanced 4-wire line (X-coupled) to prevent mutual coupling to other cables.

    The name also refers to the Max-i-mum performance, which by far exceeds comparable fieldbus systems on most fields.

  • It uses bit-wise bus arbitration, which has many very important benefits compared to for example token passing, summation-frame and time division multiple access (TDMA) systems and of course also master-slave (single master) systems:

    • Bit-wise bus arbitration is the only multi drop technology (not point-to-point), which does not need any reconfiguration when devices are added or removed! In this way, devices may be added and removed at any time on the fly without any need to stop the process. This is of course very important during production and to be able to add debuggers during commissioning, but also for applications like "Internet Of Things" (IoT) where the new devices may be mobile phones, tablets etc. In all other systems, a new device needs to be inserted in the communication sequence before any direct communication is possible (not through a common device), and if a device is removed without reconfiguration or fails, time is lost forever. In a token passing system, it may even stop all communication until the system has been reconfigurated.

    • The responce time is much faster for the same speed. A device on a master-slave, token passing or TDMA bus needs to wait for a poll, the token or the time slot before it can send a message.

    • The bandwidth utilization is much better since no time is lost on devices, which do not need communication.

    • The failure tolerance is much higher since there is no dedicated master unit, no need for a centralized database and no device needs to insert a new token if the token is lost. Since Max-i uses voltage clamps in each device instead of resistor termination, the cable may even be cut in two or more parts and each part will still work if they are poweret up and still fulfill the requirement about maximum cable length without devices (voltage clamps).

    • It is possible to use many different protocols simultaneously. On Max-i, it is for example possible to run any CAN protocol like DeviceNet or CANOpen together with the Max-i protocol. In a master-slave system, the master needs to understand all communication if it should know what to do with the data.

    The disadvantage is the time needed to do bus arbitration, but since Max-i does not use termination resistors, the minimum bit width is anyway set by the propagation delay of the line, so there is almost no overhead due to bus arbitration.

    When more devices drive a long transmission line simultaneously, there may also be problems with DC-offset, and due to the laws of nature, there is an unavoidable line ringing/oscillation on the line between the driving devices. This makes CAN very problematic to use on longer distances and without a common chassis, which it is also not designed for, but to get rid of the DC-offset, Max-i uses a virtual midpoint between the supply rails as reference, and the voltage clamp in each device removes the majority of the harmfull ringing/oscillation and a digital filter handles the rest.

  • It uses the very efficient publisher-subscriber model, where it is not the various devices, which have an address (identifier), but the various values. In this way, the same value may be utilized by any number of devices and without any mutual delays, and it is not necessary to add a long list of source and destination adresses when gateways are used.

  • It is the first fieldbus designed directly for highly demanding safety applications according to IEC 61508 SIL 3. Many fieldbus systems are approved to this level, but they all obtain that by means of an additional safety protocol on top of the fieldbus, separate safety monitors etc.

    In Max-i, all data processing for simple functions supported by the chip like (4-bit) Boolean I/O (used for safety applications), A/D and D/A conversion, UART and SPI interface, keypad scanning and advanced lamp driving is done entirely in hardware, which cannot "go down" in the same way as software and is much more predictable and failure tolerant. If a transistor fails, you will only lose the function(s) that transistor is a part of, and in case of majority-voting, the function may even be retained. In a microprocessor, all data processing is done in the same core (CPU) and it may be possible for one program to overwrite the memory of other programs so it is very likely that you lose everything.

    Because of the hardware-based architecture, the reliability of a Max-i-connected I/O channel is as high as the internal parallel or serial bus in a microprocessor plus the necessary I/O cards, which usually use opto couplers. This enables the replacement of hundreds of cables and conductors with a few fieldbus cables without any sacrifice in reliability. This level of reliability is not possible with any fieldbus, which needs a microprocessor to handle the protocol stack on the I/O side or needs routers, that is, almost any other fieldbus including ethernet!

  • It combines the outstanding performance with a remarkable simplicity. There are just a few registers to setup and a new numbering system - PNS, which allows the various process values to be addressed directly as properties of the equipment to which they belong like for example HX127AT4 for Heat Exchanger 127A Temperature 4. The Max-i specification fills only 214 pages where approximately half is used for background material and annexes. As a comparison, most other fieldbus systems have specifications way over 1000 pages, which requires several months to study and implement.

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

    Released specifications can be downloaded from this page and used free of charge for all non-commercial use. Commercial use requires membership of Max-i Association.


Highly Improved CAN

Max-i is very similar to CAN, which - as far as we know - is the only other event driven multi-master bus based on bit-wise bus arbitration except for the old, obsolete STL-Net, but as can be seen from the table below, it is not just much cheaper, but also much more powerful, reliable and safe.

Comparison between CAN and Max-i CAN Max-i
Economy Possibility for cheap, single chip interface No Yes
Product certification and registration needed Most protocols Not necessary
Use of cheap, unshielded, standard installation cables No Yes
Maximum practical power transfer per segment 384 W at 24 V 1) ≥1500 W at 20 V 1)
Maximum practical number of devices per bus 64-127 ≈1000
Environment Power saving mode / sleep mode (≤0.5 mA) Only partial network Not necessary
Group control No 255 groups
Data Multiple master bus with bit wise bus arbitration Yes Yes
Publisher/subscriber model Partly 2) Yes
Identifier length 11 or 29 bit 12 or 31 bit
Multiple use of same identifier No 3) Yes 3)
Number of addressing modes per identifier 1 4
Local and global data and global poll of local data No Yes
Possibility for temporary change of (erroneous) values No Yes 4)
Maximum number of bytes 8 1028 or infinite
Different data to more devices in same telegram No Yes 5)
Specified layers of OSI 7-layer model 1, 2 1, 2, 3, 4, 6, 7
Setup attributes per I/O (OSI layer 6) 0 16-1024
Reliability Unshielded cable = no ground loops and potential equalization No Yes
No termination resistors = high failure tolerance No Yes 6)
No bias distortion at capacitive loads (symmetrical drive) No Yes
Line-ringing between devices during bus arbitration High, but damped Low (short pulses)
Sensitivity to voltage drops in negative supply line High 7) Low 7)
Uncritical timing on all bus length and nothing to setup No Yes
Timing not affected by galvanic separation/insulation No Yes
Tolerant to contact or conductor failure No Up to 2 contacts 8)
Contact fritting No 9) 0.15 - 0.2 µm 9)
Typical transmitter power / total power loss 0.2 W / 0.4 W 6.8 W / 1-1.6 W 10)
Receiver hysteresis 0.1-0.2 V ±1 V, 3-level
Sensitivity to vibrations and low temperatures Crystal oscillator RC oscillator
Safety Error detection 15-bit BCH (CRC) 11) 20-bit CRC
Protection against masquerading (wrong identifier) No 7-bit Hamming code
Detection of wrong number of telegrams No 7-bit serial number
Predictable response time (babbling idiot protection) No Yes, deterministic
Designed for IEC 61508 SIL 3 without additional layers No Yes
Speed 4-bit / 20-bit polled values/s on a 1 km line 612 / 530
4-bit / 20-bit polled values/s on a 1.5 km line (1.5 times slower) 480 / 350 12)
4-bit / 20-bit event driven values/s on a 1 km line 1136 / 880 13)
4-bit / 20-bit event driven values/s on a 1.5 km line 480 / 350 12)
4-bit / 20-bit polled values/s at maximum speed 9800 / 8472 30500 / 17600 12)
4-bit / 20-bit event driven values/s at maximum speed 18176 / 14080 13) 30500 / 17600 12)

1) 1500 W requires 5 x 4 mm2 flat cables and two power supplies - one from each end. For the 384 W power level, CAN requires a very expensive thick DeviceNet cable (12.2 mm with 15 AWG / 1.65 mm2 conductors for DC).

2) CAN uses the publisher/subscriber model, but many protocols such as DeviceNet and CANopen need to establish a communication channel between devices before communication can take place and may even divide the network into masters and slaves.

3) Without this feature, it is not possible to make for example two-way/landing switches for LED lighting, and it is not possible to have more control buttons for the same process function or the same function in for example coupled trains, but most (all) CAN protocols such as DeviceNet and CANopen actually has a feature to prevent multiple use of the same identifier!

4) Most process values use 4, 20 or 36 bits, and it is possible to change a value temporary, which can save a lot of time during commissioning in case of sensor errors. It also makes it possible to run tests without material simply by simulating the presence of material.

5) Max-i can send individual 8-bit, 16-bit, 24-bit or 32-bit values to more devices in a common telegram with up to 1028 bytes and in this way ensure 100% data synchronization and a very high efficiency for example for motion control, positioning systems and for stage light control where Max-i with advantage can replace DMX512. CAN is only able to transmit 8 bytes in each telegram and is therefore not able to synchronize more than two servo axes with 32-bit precision.

6) In Max-i, the traditional termination resistors have been replaced by voltage clamps in each device. This gives a very high failure tolerance even without multiple communication lines as the bus may be cut in as many parts as there are power supplies, and each part will still work! The clamps also remove excess power during bus arbitration and therefore reduce the ringing, they reduce the power loss in the line termination to approximately the half compared to termination resistors and they utilize the reflections to improve the signal waveform and prevent bias-distortion due to noise rectification.

7) The CAN transceiver is usually connected to the negative supply line so a voltage drop on this line causes bias distortion. Max-i uses the midpoint between the power supply lines as 0-V reference, but must then require that the voltage drop in the two lines are approximately the same.

8) In case of a balanced 4-wire line, where the two communication conductors are connected together in all devices, Max-i will usually survive a failure on one of these conductors or connectors. If more power supplies are used, Max-i may also survive a failure on one of the supply lines so that Max-i is able to survive a failure on two neighbor conductors or connectors.

9) Usually, a fritting voltage of approximately 100 V/µm is required to burn through contact corrosion. Since the supply and communication voltage of Max-i is approximately 20 V, approximately 0.2 µm can be accepted. Below 3-5 V, no fritting can be expected. This makes CAN inexpedient for connections between for example tractors and trailers (trucks) and between train wagons.

10) When a transmitter is activated, two waves are generated with a typical power of 3.4 W in each direction. Because Max-i does not use any termination resistors, the current in each wave falls to zero after the time it takes for the wave to travel to the end of the line and back again to the transmitter. If for example a device is placed in the middle of the line, the two waves will arrive simultaneously, so the power will fall from a total of 6.8 W to zero after a time corresponding to the propagation delay of the line. If the device is placed at the end of the line, one wave arrives immediately, so the power falls from 3.4 W to zero after a time corresponding to two times the propagation delay. No matter where a device is located on the line, the energy (power multiplied by time) is the same, and if the line is shorter than the maximum length, the energy is reduced correspondingly. This reduces the emitted noise and enables battery operation and operation in explosive atmosphere. The power loss in the transmitter and the clamps depend on the supply voltage and the sum is maximum at maximum voltage.

11) In CAN, two bit errors may on rare occasion remain undetected when the first generates a bit stuffing condition and the second then removes a stuff condition (or vice versa), shifting the position of the frame bits between the two bit errors. The shifted area may lead to a burst error that is too long for the CRC mechanism.

12) In Max-i, it does not take longer time to poll a value than to transmit it event driven as the first and last part of the telegram are just transmitted by two or more devices.

13) Because CAN does not have any "babbling idiot" protection, it is not possible to reach this number of telegrams in practice without a completely unpredictable delay of low priority telegrams. Max-i may run even at 100% and is faster than CAN for safety telegrams where CAN needs an extra layer and it is much faster if the possibility for different data to more devices in the same telegram is utilized as it is the case for stage light and motion control systems.


Supplement to Ethernet

Ethernet is growing fast in industrial process control. This puts traditional 5-V based fieldbus systems under pressure. Because they need a power supply to convert the supply voltage to 5 V, a timing crystal and some microprocessor assistance to handle the communication stack, they are too big and expensive to be included in the smallest and most price sensitive devices like push buttons, lamps, micro switches, motor contactors etc. It is therefore only possible to use these bus systems for distributed I/O and for connection to more complicated devices, but Ethernet can do that too at very much the same price. There may even be Ethernet in the building already, which may save some money for cabling. Ethernet will however never get out to individual actuators and sensors - even if the price and size is not taken into consideration. Because Ethernet is today a point-to-point communication, the signals in a big plant would have to pass so many routers and with that so many cable connectors and so much electronics that the reliability would fall to a totally unacceptable level with maybe up to one failure per week.

In the future, there will therefore probably only be room for two types of bus systems - Ethernet with an added layer to make it deterministic like Ethernet PowerLink, EtherCAD, ProfiNet, Ethernet/IP, Time Sensitive Networking (TSN) or Sercos, and an ultra-low-cost, but still high performance and deterministic bus system for connection to individual actuators, sensors and lamps. This bus system must:

  • Be deterministic.

  • Be cheap and small enough for even the smallest and most price sensitive devices as these devices by far make up the majority of devices in most plants. A vendor of a complex device may find it easy to add for example a CANOpen or Profibus Interface if the device already contains a power supply and a sufficient powerful microprocessor with bus controller, and the necessary software stack is available, but selecting a bus system, which is too complex for simple devices on the same bus, will not lead to an optimized total solution.

  • Be powerful enough for even very complex and demanding devices like mass flow gauges and motion/motor control. On a 35 m trunk line, Max-i is able to synchronize 7 servo motor axes with 32-bit precision to an accuracy of 0.1 μs at an industrial state-of-the-art communication cycle of 400 μs. This is much faster than CAN and close to or even better than the performance of a much more expensive and complex Ethernet solution, which also has much lower reliability due to the necessary routers and other complicated electronics.

  • Be able to supply enough power for even big actuators and lamps where more amperes may be needed and do it in a cost efficient way. This demand excludes all fieldbus systems, which use special communication cables. A lot of fieldbus systems are really only sensor busses due to the low power or the use of communication methods, which do not allow switching of heavy loads, but in a typical process plant there are only approximately 1.5-2 times more inputs than outputs, so a bus, which does not take the actuator side seriously, will not lead to an optimized solution.

With its outstanding versatility, Max-i is so far the only fieldbus, which fulfills all these demands!


Internet of Things and
the House of the Future

Internet of Things (IoT) has become the new buzz-word, but there is really not much new in that. For years, thousands of industrial process signals have been available on the internet - simply because it is very practical and saves a lot of time and money to be able to perform remote service. There is also nothing new in controlling the various devices in an intelligent manner. In the industry, this has been done by means of for example programmable logic controllers for over 40 years.

In the home, you may for example connect the coffee maker and the refrigerator to the internet and control the light from an App on your smart phone, but although such technology has been available for years - I/O Consulting (now Prevas) connected a coffee maker back in 1998 - most people don't care about IoT except for a few geeks, who may use it to impress their friends. In daily life, it simply gives too less value for the extra money needed to put a device on the internet and it doesn't solve problems like the very fast growing chaos of charger and converter boxes with related cable spaghetti and the fairly high cost and size of today's LED lighting. It also doesn't give you any environmental improvements like the possibility to drive LED lighting, window openers, door locks, PC's and PC peripherals etc. from solar panels, and in case of wireless systems, it may even open a wide backdoor into the system, which hackers may use to entirely overtake your computers in seconds.

The only area where IoT makes sense to most people is alarm systems, but this is an area where present IoT technology based on wireless communication and small batteries in each device is least suitable:

  • 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 a wireless system is jammed, an alarm must be generated immediately or at least within approximately 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, which makes such a system quite useless in practice.

  • Wireless communication is very easy to jam and may generate many false alarms due to other wireless communication in the same frequency band. False alarms are not only very irritating, but they also makes you nervous.

  • It can be very difficult to ensure that wireless communication do not disclose information about for example when your home is empty or transmit unwanted information about your behavior to third parties. This is especially a problem with alarm systems with cameras where it is almost imposible to guarantee that your behaviour in your home is never transmitted to third parties or transmitted to second parties such as alarm centers when you don't want it. If you connect a camera and don't set the security code immediately or forget it, you may find a nice picture of your home half an hour later on a russian web-site. There is an example of that! Everybody may be able to see exactly, when you leave your home, and it can be very embarrassing with for example a public video transmission from your bed room. Some cameras have a red light showing when the camera is recording, but it may be switched off to hide the position of the camera, and a hacker may also be able to switch it off if he is able to penetrate into the system.

  • The wireless connection may be used to hack into the system even from a long distance, and the safety is not better than the weakest link. 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, and the majority of IoT devices are not updated after some time or not at all so safety holes will usually not be fixed!
  • Battery driven systems have only enough power for simple, low-power sensors such as infrared detectors, but these kind of detectors generate many false alarms and may be false triggered by temperatures as low as 28 °C. Cameras are a very good solution to avoid false alarms, but due to privacy, it is not a good idea to transmit the raw picture. A much better solution is to use modern person and face recognition technics and then just send the alarm and perhaps the necessary parameters to possibly identify the person. However, image processing requires a lot of power as many people know from their smart phones, which can discharge the battery very fast and even get quite hot when working with pictures or videos, so such intelligent sensors are not possible.

With Max-i, it is different. Since it is a combination between a low-voltage DC power supply and a communication network, it has all the power needed for even the most advanced alarm system, it can simultaneously control the lamps to make the home looks inhabited and/or destroy the night vision of a thief, and it can be used for many other purposes than just IoT and therefore offers much more value for money. It is very easy to build fail-safe networks up to very high safety standards, it is easy to log all communication so that you can be absolutely sure that no device transmits unwanted information behind your back and you can just disconnect the internet when you don't need it and in this way keep even the best hacker out. Unlike for example WiFi, there is also virtually no limitations on how many devices you can connect without any noticeable degrade of performance.

If devices only did what they are expected to do like the majority of Max-i devices, which are entirely hardware based and therefore cannot do anything else, and the receiver only allowed data corresponding to the added sensors, the problem would not be so big, but virtually all wireless devices contain a microprocessor, which can easily be reprogrammed by hackers, and the receivers are often general purpose devices, which may allow many other functions than expected. If you have a wireless keyboard or mouse, just try to search the internet for "mousejack". A $15 dongle and 15 lines of Python code may be enough to entirely overtake your computer in seconds from over 100 m away!

With Max-i, it is possible to bring decades of industrial experience into the home without any compromise on security.

For developers or just makers, who wants to play with home automation, the extreme simplicity of Max-i and the easy connection to most small computer systems will be a completely new feeling compared to any other IoT and home automation technologies. There is no need to download and maybe pay for very big design suites, study specifications, new operative systems and user manuals with way over 1000 pages for months and finaly go through an expensive and time consuming conformance test before your product is ready for sale. In the future, you just buy a Max-i chip, put it into your device and program a few registers over the bus (no special programming tools needed). For the majority of devices, where the function is supported by the chip such as most buttons and keypads, lamps, actuators and sensors, you can have a prototype ready in a few hours - even if you have not used Max-i before. This also makes it possible to use Max-i technology for companies without programmers. If you for example want to make a multi-color lamp, you just need a Max-i chip and a few capacitors plus a current generator (can be a single transistor plus a resistor) with 4 - 5 serial connected LED's for each color (up to RGBWaAaC). Home automation and IoT has never been, and will never be, simpler and cheaper than that.


No Charger or
Converter Chaos

Today, most homes have a very fast growing chaos of clumsy charger and converter boxes with related cable spaghetti and outlet distribution boxes for smartphones, tablets, laptop computers, computer peripherals, cameras, LED lamps and lighting, toys etc. This really does not look very nice and makes it impossible to vacuum clean and therefore does not have any "woman acceptance factor" (WAF), generates a lot of electrical noise, creates an increasing fire risk due to the often very doubtful quality and cooling and destroys the smartness of the new, compact technology. It does not make much sense to buy for example an expensive only 17 mm thick laptop PC, and then bring a heavy and big brick of a charger with. Besides, due to the laws of nature, the efficiency of many small converters is way below what can be achieved with fewer devices with higher power - especially if 50 Hz transformers are used, so a lot of power may be wasted, and many of these small converters have been shown to be very noise sensitive and in many cases cut off for a short period of time in case of voltage transients or voltage drops.

Max-i offers the ideal solution to that. The high power and use of standard installation cables also makes Max-i extremely suited as a supplementary 20 Vdc power supply and control in the houses of the future where it may be used not only for intelligent LED lighting and all kinds of battery chargers including all levels of USB Power Delivery and Quick Charge, but also for window openers and energy management and alarm systems such as fire, smoke, burglary, water and power failure. Calculations done by the Danish engineering company Rambøll shows that such a network partly driven by solar cells can save the Danish households in the order of 1 billion Danish kroner per year corresponding to approximately $150,000,000.

Max-i has all the features needed for these kinds of applications. For example, it is very easy to make two-way/landing switches and light dimmers with the LED controller and all Boolean outputs may be divided in up to 255 groups, which may be switched off in three steps for example during lunch breaks, when you leave a building or in case of failing "green" energy supply or a heavily loaded power net.


Environmental Friendly

LED lighting is usually considered environmental friendly, but the necessary mains voltage converter requires many production resources and reduces the life time considerably, and the use of for example toxic epoxy boards and big components makes it very difficult and expensive to recycle with the result that they often just end up in the incinerator or even on the landfill. Due to the high voltage levels and often rather low quality there may even be a fire risk and many converters generate a lot of electrical noise. However, with a 20-Vdc net, a LED lamp only needs a simple series connection of 4 or 5 LED's and a linear current generator per color plus a Max-i controller if remote control is wanted. Such a solution can reach an efficiency of 75 - 80 %, and although this may be slightly lower than possible with a state-of-the-art switch-mode converter, the total environmental account becomes much better - especially because all components can easily be monted on the aluminum LED assembly, which is very easy to recycle. Besides, such a solution is much cheaper and smaller and can be contained in even the smallest and most architectural designed lamps, and because the full life time of the LED's can easily be utilized, it may not be necessary to be able to replace the light source.

Many people wants to drive everything from their own solar panels including induction stoves, microwave ovens, washing machines, vacuum cleaners and maybe even chargers for electric cars, but due to the necessary inverter and the size of the solar panels and any batteries, it is an extremely expensive solution, which may even destroy the look of the house. Besides, the efficiency is usually very low during periods with low power consumption, which may make it very inefficient to use the energy in own batteries. An inverter big enough to drive for example a 10-kW induction stove may have an idle power loss much bigger than for example the power needed for LED lighting, so unless you can simultaneously sell power to the mains and in this way increase the load on the inverter, which will however simultaneously wear and tear the expensive batteries, it may be nothing but loss! However, in a typical house without electrical heating, approximately 65 % of the electrical power is used for low-power devices like LED-lighting, entertainment and computer systems with peripherals, low-energy refrigerators and freezers with variable speed compressors, window openers, sun shading, alarm systems, access control and all kinds of chargers. Such devices can easily and with benefits be driven from 20 Vdc, so instead of reaching for the entire 100 %, it is much cheaper to forget the peak power and only to go for the remaining approximately 65 %. With a sufficient number of solar panels, it may be possible to drive these 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 so that additional heating is not needed most of the year. A cold-air outlet from such a pump with a temperature close to 0°C or lower may even be used for a compressor-less refrigerator so that the last power and efficiency can be squeezed out of the system.

Since the charging voltage of Max-i fits very well with the maximum-power-voltage of 54-cell (or 60-cell) solar panels, such panels may be connected directly with almost the same efficiency as complicated switch-mode electronics. This further reduces the price, the electrical noise and the amount of electronics to manufacture and recycle and it increases the reliability. By means of a simple Max-i controlled switch to connect each panel, the charging current may easily be controlled in steps of typical 30 - 170 W, which is in the same order of magnitude as the maximum 100 W of each outlet. Besides, since the voltage is always lower than approximately 35 - 40 V (open circuit voltage of panels), the arc risk is very low and there is never any shock hazard even in case of fire extinguishing by means og water, which may be very dangerous on traditional serial connected systems.

In total, Max-i offers maximum "greenness" and value for the money!


LED controller

Max-i includes a very advanced LED controller with a lot of features:

  • Suitable for even the most demanding stage light and architectural lighting applications (DMX512 replacement).
  • Pulse code modulation with 1.25 µs pulses (not PWM) for very small decoupling capacitors, no flicker or stroboscopic effects and very long LED life (less thermal stress).
  • No violation of the Philips PWM patent for color changing (RGB) lamps or the similar Infineon sigma-delta patent.
  • 4 x 8-bit, 6-color RGBWaAaC system with automatic generation of artificial amber (aA) and artificial cyan (aC) on the basis of RGB.
  • Build-in gamma correction of 2.44 to increase the contrast ratio and keep the color hue constant during dimming.
  • Contrast ratio of over 11,000:1.
  • 3rd order smoothing filter on each color with 7 time constants (bypass, 2.5 ms, 5 ms, 10 ms, 20 ms, 40 ms, 80 ms and 160 ms), which may be selected on a per-telegram basis.
  • 6-bit dot correction on each color removes the necessity for expensive bin selected LED's.
  • Integrated one-button light dimmer with 60 levels, night light and possibility for synchronized two-way/landing switches.
  • Daylight control (dimming) in up to 255 groups with all-off (and all-on) function and slow smoothing filter to convert the 60 levels to 240 steps and in this way make each step invisible.
  • Integrated traffic light controller with dimming, programmable minimum level and green safety output.

The very advanced controller has previously unseen control possibilities. Without changing the settings, a lamp can simultaneously be controlled and dimmed by means of wall switches and automatic daylight control, be set to a specified color for example by means of a mobile phone or tablet and be controlled together with other lamps in a common group telegram with individual reception delay to set a scene or even control the lamps in real time from for example a TV set or a computer with the same speed and performance as professional stage light.

With the 6-color RGBWaAaC system, which can generate excellent pastel colors, and the possibility to address many light sources in the same telegram, the lamp controller is perfect for illuminated ceiling panels with diffused light where it can create an illusion of being outside with drifting clouds and varying color temperature depending on the time of the day. This may for example be used to create a pleasant feeling in stores, treatment rooms in hospitals and in rooms without daylight such as rooms in the basement.

The ceiling may simultaneously hide alarm sensors etc., which can just be connected to the same bus.

If 6 colors are not enough, any number of Max-i controllers can very easily collaborate by means of common telegrams. Just two controllers where the reception in one is delayed 4 bytes can create an absolute state-of-the-art 8-color system (plus 4 artificial colors) at a previously unseen low cost. With for example a royal-blue, artificial blue, cyan, green, lime, amber, orange, red and deep red system, any color and color temperature can be created with excellent accuracy for example for lighting in art museums etc. Because of the inherent possibility for battery backup, the lamps for such applications can simultaneously be used for emergency lighting, which can even show the way to the nearest exit by means of running light for example controlled by means of a common group telegram. In case of smoke where white light is scattered, the light may even change to red or reddish, which makes it easier to find the way out. If the lamps are equipped with sensors, they can simultaneously be used for alarm systems for example for burglary and fire so that only a single lamp unit may do it all.


Trafic Lights

For many reasons, Max-i is perfect for driving traffic lights:

  • It makes it possible to replace all the expensive and thick multi-core cables and belonging connection boxes with a single balanced 4-wire loop.
  • It saves all the expensive controller-I/O for point-to-point connections to the lamps. This saves a lot of money too and makes it possible to drive everything from a microprocessor with the size of a credit card.
  • It is very easy to connect a laptop PC or tablet to the bus for programming and debugging so there is no need for an operation panel.
  • The excellent dimming possibilities with group control and programmable minimum level makes it easy to optimize the light intensity in each direction according to the ambient light and solar radiation in that direction. This can save a lot of power and prevent dazzling of the drivers at night.
  • The inherent possibility for battery operation can easily prevent the trafic from breaking down in case of a power failure. This is especially important in critical situations like terror where a loss of trafic lights very fast makes it imposible to evacuate people and get rescue vehicles and police through.
  • In case of a power failure, the lamps can be dimmed to save power and in this way make the batteries last much longer.
  • The publisher-subscriber mode makes it possible to update all lamps i one direction simultaneously.
  • The 4-bit boolean values fits perfectly with the usual number of lamps in a lantern (in one direction).
  • It is designed for maximum safety according to IEC 61508 SIL 3 (death of 1-3 persons) and even has a green safety output with own decoding circuit to prevent green light in case of a failure.


Military Applications

Strong electromagnetic fields may be very destructive for most kinds of electronics. This is utilized in various kinds of electromagnetic weapons. One of the most powerful discharges occurs when a nuclear weapon is detonated in the upper atmosphere. This creates an electromagnetic pulse (EMP) with field strength up to approximately 50 kV/m, a rise time of 5 ns and a duration of approximately 1 µs. One way to survive such a pulse is to keep the system fully balanced - even in case of very high voltage levels (good insulation) - and keep the physical dimensions very small and this is exactly what Max-i can offer. With a well insulated 4-wire cable and a very small (single chip) interface, there is a good chance that the system will survive. A field strength of 50 kV/m is only 50 V/mm, so a chip with a size of 1 × 1 mm will be exposed to a maximum of 70 V (diagonally), which is in the same order of magnitude as the maximum working voltage and therefore easy to limit.


Evaluation Board

Until the final IC solution is available, Innovatic can offer an evaluation board - EB1, which simulates a Max-i IC by means of an FPGA and other standard components. This solution may be very interesting for vendors, who want to take the step into the future and have a possibility to influence the standard before the IC is made. It may also be interesting for semiconductor companies, who may be looking for a new product family and/or can see the enormous potential in one fieldbus for virtually all low to medium speed applications from the most price sensitive ones to the most demanding. Because EB1 was designed for a previous version of the specification, it is not using 20 V, but only 12 V, and it has only 2 inputs and 3 outputs, but a new 20-V board with 8 inputs and 8 outputs, which can also be used for products (not just evaluation) is under development and expected to be released in Q2 2020.