Nexa is a radio based system for remote control of switches and dimmers. Nexa is really just one of the names this system is sold under. The actual devices are made by ArcTec, but branded by resellers in Europe and US. It is also sold under the product names: Chacon, Elro AB600 and Proove. The system also includes PIR-detectors, magnet switches for windows and other detectors which work as remotes and can control the switches.

Nexa has two addressing systems, one old where devices are explicitly given a house code and device code with code wheels and one newer “self learning” system where transmitters have unique addresses and the receivers “learn” the code of the sender which is controlling it. NetHomeServer supports both variants, which in reality are two entirely different protocols.

The Nexa system have no native computer interface. It does however use the standard 433MHz radio band (in Europe), which makes it possible to use the generic 433MHz receiver and sender of the NetHomeServer to send and receive commands to and from Nexa devices.

You can use the NetHomeServer CUL Connection for sending the radio control messages

You can also use the AudioProtocolParser and the AudioProtocolTransmitter interface modules. Currently you will have to build the hardware for the actual transmitters and receivers yourself, but it is quite easy done by modifying existing products.

• Building receiver is done by modifying an UPM thermometer
• Building a transmitter is done by modifying a Nexa remote control

The NetHomeServer can act in several roles with the Nexa-system:

• Remote control of devices - you can switch on and off lamps via the WEB-interfaces
• Interface module - via the NetHomeServers interfaces (TCP/IP, SOAP UDP/IP) you can let other software control the lamps
• Nexa Home Automation - via NetHomeServer:s timers and other control objects you can automate and link events to actions on Nexa-controlled appliances.
• Home integration - let Nexa wall switches and PIR-detectors control other actions or remote systems via the NetHomeServer

The Nexa-Related objects in the NetHomeServer are:

• NexaLamp Controls a dimmer or a switch
• NexaRemapButton Lets you control other Items with a Nexa remote control
• NexaLCLamp Controls a dimmer or a switch using the Learning Code protocol
• AudioProtocolParser General protocol receiver using the microphone input, used to receive Nexa radio signals
• AudioProtocolTransmitter General protocol transmitter using the audio output of the PC to send RF-signal and control Nexa switches.
• CULTransceiver Interfaces with the CUL RF transmitter

The old Nexa system where you manually set the adresses has a big limitation in the way dimmers are controlled which makes computer controlled dimming of Nexa devices practically impossible. The self learning version however has excellent support for dimming to an absolute level.

Dimming of an old Nexa Device is done by holding down the button of the remote control for a while - this starts the “dim mode” where the dim level constantly rises and falls. When the wanted dim level is reached, you press the button again to freeze the current level. This means you actually have to see the lamp while dimming and it needs very low latency on the control (to stop at the right moment). This makes it difficult to use in computer controlled remote control applications. The on/off function however is good, in the sense that it has separate on and off commands (not just toggle), this is very good for computer control. See system comparison page for comparison with other remote control systems.