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:
C:\Programs Files (x86)\lonworks\bin.
..\smartserver-iot\apps\Dsp SP Controller Example\Internal App EVB files. This directory branch was created when you cloned the github repo: https://github.com/izot/smartserver-iot .
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.
..\smartserver-iot\apps\Dsp SP Controller Example\Internal App EVB fileand in the address bar type
cmdto launch a Windows command window with this folder as the current working directory.
nodeutil -dx.default.[rni name]where [rni name] is the name you used in step 6 above (RNI).
gand select device 1.
yand 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.
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).
..\smartserver-iot\apps\Dsp SP Controller Example\Internal App EVB fileswill heartbeat as 120s.
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.
Return to Creating a Custom LON App.