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MAXX :: NODEs
   

 

Nodes allow a generic hub enclosure to have a custom configuration by just plugging in the combination of IO that is appropriate for the application.

 

Nodes are very small, most currently designed nodules fit onto a 41x37mm PCB. Up to four nodes can fit into a single hub (limited only by the current enclosure, there is no practical electronic limit so other physical formats could have many more nodes) and share the network interface provided by the hub's interface PCB.

Nodes can be designed to perform any IO function, and many standard functions are currently at the design stage. Because nodes can be isolated (by adding an isolated interface to a hub) they can be used to measure high-side voltages and currents or even mains-level voltages with a high degree of safety.

MAXX nodes normally have a PIPE processor, an application processor and a small amount of logic to implement the nodule's IO. However for very simple functions a PIPE can be used in stand-alone mode in which case no application processor is required.

Current designs use a 32-bit LPC1227 for the application processor. The use of such a powerful processor may be considered an overkill but it will allow an node to perform many signal-conditioning and data averaging functions, thus taking a load off any system controller.


   
    nodes currently being designed    
   
At present a range of nodes to cover basic monitoring and control functions are being designed.
  • ACCELEROMETER - A 3-axis accelerometer.
  • ALARM - Audio and optical alarm function.
  • AMPS - This node uses two hall effect sensors to measure two separate currents up to ±20A. The contacts are isolated.
  • COUNT - High-speed counting of period, frequency and pulse widths.
  • DISP-7SEG - A simple node with four .8" (20.4mm) 7-segment displays, colon and minus indicators, and four pushbuttons. (non-standard physical format designed for a different enclosure)
  • GPIO - 12 general-purpose digital in/outputs and 6 analogue inputs.
  • GPS - Features a GPS module. NMEA sentences are parse by the node and presented to the network in a simple format.
  • DISP-LCD - An 8x2, 16x2 or 20x4 LCD display.(non-standard physical format designed for a different enclosure)
  • PROTO - A double-sized node that is Arduino compatible, to be used for prototyping.
  • PSU - Provides 12 or 24V power to the network.
  • RELAY - Two pairs of voltage-free contacts.
  • RS232 - A DB9 connector and a MAX232 chip to provide full RS-232 levels for RX, TX, RTS and CTS.
  • RTC - A highly accurate real time clock.
  • SHUNT - This node is designed to amplify and read the voltage across two current shunts. The shunts can be high side (65v) or low side.
  • TCOUPLE - For measuring temperatures up to 1000°C
  • TEMP - Measures 4 temperatures in the range -55 to +150°C.
  • USB - A USB gateway to the network for a computer.
  • VOLTS - Six analogue inputs that can read voltages up to 30v with 10-bit (approx 30mV) resolution.

 

   
    PCB    
   


The standard node PCB is 1/4 the size of the enclosure's internal dimensions.

Corner bevels allow clearance for the enclosure's centre column regardless of the node's position.

The green section is outside the enclosure and available for connectors. The two yellow sections are reserved for the backplane connectors. What remains is for use by the node's circuitry. It's not a huge area but with modern components on both sides a lot can be done.

If more space is required for a given application a double-sized node can be used.

 

Mezzanine nodes

An node that doesn't have a need to use external connectors can be mounted on top of the other node and it can occupy the entire internal space of the enclosure. Such an node must implement the backplane (the four yellow areas) but apart from that you are free to use the entire 75x55mm area.

Some typical examples are an RTC, GPS, Xbee or other wireless, SD data logger, accelerometer, compass etc. None of these need access to connectors and can therefore be accommodated with an internal node. Of course none of the above examples would need a board this large, but as long as the backplane is implemented the board can be any size you like up to the maximum.

 

   
 

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