This example uses the FT 6050 Evaluation boards on the IzoT FT 6000 evaluation kit as a target network of devices simulating a VAV-based HVAC system. Such systems commonly include 10-30 VAV controllers and a Discharge Air controller that, as part of its sequence of operation, will modulate the fan speed of the building air handler to maintain a specific duct static pressure. In simplistic operating sequences, the set point for duct static pressure is constant. For example, 2.5 inches of water (623 Pascals).

As demand for all the VAV zones is satisfied, there is potential energy savings by resetting the duct static pressure to a lower value. The VAV controller includes a data point that uses SNVT_hvac_status to report the operating demands of that zone to allow an area controller to calculate appropriate operating set points for duct static pressure, supply air temperature, hot water temperature for re-heat, and pressure for hot water supply circulation. This example focuses on duct static pressure.

An example VAV simulation is shown below. With just 2 FT-6050 EVB boards, you can build a network to follow the example.

You need to have the following software running on a Windows computer to setup the example network:

Setup SmartServer IoT RNI Feature

The SmartServer must be set up to support access by nodeutil.exe so you can download the example application images to the FT 6050 EVBs. 

  1. Log in to the SmartServer IoT configuration interface using the apollo user credential. 

  2. Select the Features tab, and select Enable, and optionally the Protocol Analyzer port
  3. Commit these features by clicking the Update button.

  4. From the Windows Control Panel, launch the LonWorks Interfaces (32-bit) applet.
  5. Select Add and then the RNI interface type.
  6. Provide a name for your RNI (using RNI below) and the host name or IP address for your SmartServer IoT.
  7. Click OK to save.

  8. Select the RNI interface you just created, and verify that your computer can connect using the Test button. 
  9. Review the results in the status pane and make any corrections to the interface you defined as needed.

  10. In File Explorer, navigate to the folder ..\smartserver-iot\apps\Dsp SP Controller Example\Internal App EVB file and in the address bar type cmd to launch a Windows command window with this folder as the current working directory.  

  11. Type: nodeutil -dx.default.[rni name] where [rni name] is the name you used in step 6 above (RNI).

  12. Press the service pins for each  FT 6050 or FT 5000 EVB board in your test network.
     
  13. Use the command g and select device 1.

  14. Type y  and select the target .ndl file you wish to load. Take note to use the correct file based on your target EVB (FT 5000 or FT 6000). One target should be loaded with the file DACxxxx.ndl, and one or more EVBs should be loaded with VAVxxxx.ndl.

VAV Simulation Application

This application does not implement a standard functional profile template. It includes only a single input (nviDemandSim, SNVT_lev_percent) and a single output variable (nvoVAVstatus, SNVT_hvac_status).

  1. At reset, the application reports the cooling output demand of 50%. 

  2. The cooling demand will ramp the a cooling_output to 90%.

  3. An update to nviDemandSim will initiate a ramping of cooling_output reported by nvoVAVstatus at 0.1% every sec 200ms, or 1% every 2 seconds.

  4. If you press the right button on the EVB, the cooling output demand will increase. After 1 second of no button press activity, the simulator will ramp to the increased level.

  5. If you press the left button on the EVB, the cooling output demand will decrease. After 1 second of no button press activity, the simulator will ramp to a decreased demand level.

  6. While the demand is ramping, the output value reported by the network variable nvoVAVstatus will throttle update to a minimum of once every 10s.     

  7. When the final demand is reached, the variable  ..\smartserver-iot\apps\Dsp SP Controller Example\Internal App EVB files will heartbeat as 120s.

Discharge Air Controller Simulation Application

This application implements the SFPTdischargeAirController (8610) functional profile. The input nviDuctStaticSP (SNVT_press_p) is targeted by the SmartServer IoT Internal App example.

The display on the EVB board reports the current value in Pascals. The conversion factor is 1 Pascal = 0.004 014 630 786 7 inches of water. For example, 2 inches of water = 498 Pascals.

Next Step

Return to Creating a Custom LON App.