Why you should avoid a wired bus in automation

The word bus comes from the Latin word omnibus, meaning ‘for all’. Connecting a lot of devices to a pair of wires is a seductive idea. It works in computers, but automated gates are in a relatively wild environment where things go wrong.

Wiring buses simplify wiring, but have reliability issues. A wiring failure can disable any safety sensitive bus. The first power bus was the national grid introduced in the 19th century. At the lowest level, all our mains’ devices are
fused to protect supply to the rest of the house. The modern National Grid has high voltage breakers, and the ability to reroute power over whole areas. Automation buses have no such protection. One short circuit can take out the whole bus.

ADVANTAGES
So, what are the advantages of a bus? Activation inputs to a control panel are more than likely to be connected into the same terminal because they are normally open contacts. Safety devices use normal closed contacts wired in series, which requires extra connecting wires between contacts.

Digital buses interrogate each device in turn, asking for its state, and if it is a safety device, is the device working. Twoway communication ensures accuracy and safety. Polling the devices in a sequence keeps wiring simple. In comparison, an 8k2 input has one way communication, checks integrity, but
only handles one or two devices.

Any simplification to bespoke safety wiring is welcomed by the installer on the ground, but simplification must not impair the integrity of safety circuits. A safety bus is simple, but for safety’s sake, any error must disable the automation.
The elephant in the room - safety is the enemy of reliability! Every automation system is a bespoke package. Every gate is different. Until the gate is proven (force tested) experienced system designers will make wiring provision for extra safety devices. A bus is a beguiling solution, but a few extra cores of cable is flexible without the risk.

Another disadvantage is standardisation. So many elevators are out of action because “we can’t get the parts, guv”. Bus devices lock you into a particular manufacturer. No other part will fit, so you are reliant on one part from one supplier. Remember the ‘chip shortage’ in 2022? Service engineers should carry on their van what it takes to repair a system. Carrying a set of universal “old school” devices that can fit to standard wiring is efficient and good customer service.

MOTOR POWER
So, let us look into the future of automation. ACIM’s and 3 phase are out. 24V dc motors and brushless motors are in largely because ELV category voltages have a lower wiring requirement. The auto industry is having to retrain their engineers to work with the high voltages (400V-500V) used on electric vehicles. So my prediction is the use of 48V brushless motors and also compatible with solar panels. Peripheral devices, traditionally 24Vac, will drop to about 3V
to suit small solar panels, lithium-Ion batteries, and chips. New EU regulations also drive control circuits to use lower standby power.

DIGITAL MOTORS
So a digital motor could be defined as one with power and data. Came’s FROG-X motor breaks new ground. FROG-X is a brushless motor on only 3 wires, two for 24V dc power and a two way data wire. Brushless motors normally have 3 wires for the motor windings and other wires for feedback. The FROG-X data wire carries the instruction and the feedback.

This simplifies the control panel, taking out all the high current power supply and switching circuits. The control panel is reduced to a processor with two serial ports about the size of a pack of cards or a Raspberry PI.

FROG-X wasn’t an easy birth. FROG-X first ‘stepped outside the box’ in March 2022, but was withdrawn after problem in the field. Once proven, the core motor technology will be seen in other products.

WHERE NEXT?
The next logical step is to power the motor with the original power bus (240Vac) then connect by Wi-Fi - the original wireless data bus. The two bus that will be the future of automation have been with us since 1897 and 1997.
The Wi-Fi controller meanwhile needs a secure method of configuration by the installer. What better method than a mobile ‘phone app by Wi-Fi or cloud control via LTE.