404 2 Axis Installation

Considerations for Latitudes between 23 ½ N and 23 ½ S

Calibration Considerations:

This pertains to to 2 Axis Versions 404 and above and not for Single Axis or Parabolic Trough .

These lower latitudes experience different paths of the Solar Azimuth which require the tracker to operate the entire 360 range of the compass. Between the equator and 23 ½ N, the sun will rise in the east and track to the south and set in the west for most of the year. This is called a southerly path.

Near the summer equinox, in June, the sun will rise in the east moving south and then track to the north. It crosses 0 degrees north to 359 degrees and eventually sets in the west. This is called a northerly path.

This means that the tracker will operate for most of the year as all other trackers in the northern hemisphere above 23 1/2 deg. N but will behave like on in the southern hemisphere for part of the year.

azimuth

When moving along the northerly path, it is important that the controller keeps track of how it arrives in the quadrant between 270 deg. and 360 deg. so it can return in the same direction  and not wrap wiring around damaging the assembly. This is why it is important never to start operating your tracker the first time in this quadrant by manually moving it via the northern path because it will return via the southern path unless configured to do otherwise.

Tech Note:

The Tracker IPm automatically defaults to expecting a southerly path. This is reflected in register AX117 SOLAR_PATH as 0. If you have positioned the tracker to 320 deg. N via the northern path, simply change the 0 to 1. The controller constantly monitors the solar path and keeps track of this in non-volatile memory. A power loss will not affect this.

Limit Switches

The wide range of travel in the lower latitudes creates specific considerations for minimum limit switch placement. Your minimum switch cannot be placed in the east because it will prevent the tracker from tracking via the northern path. It therefore has to be placed somewhere in the northwest quadrant, ie. 290 degrees.

Set Operational Limits 2 Axis

The following instructions apply to locations above 23 1/2 degrees N and below 23 1/2 degrees south.

There are 3 Operational Limits to implement

  1. Soft Limits
  2. Mechanical or Proximity Limit Switches
  3. Night Stowage Setting

Soft limits will limit the tracker’s travel through software on both axis. If the calibration with the sun is incorrect then the soft limits will be off by the same amount so it is important calibrate the controller  before setting the soft limits. The soft limits add a degree of redundancy as a back up to mechanical limit switches. They can be configured to prohibit travel inside or outside the range of travel between the mechanical switches. Settings can be between 0-360 degrees Azimuth axis and -10 to 180 degrees Altitude axis.

SoftLimitsAZ

 

 

 

 

 

 

 

 

 

 

 

 

 

Inside the HARD LIMIT SWITCH MAX as shown in Figure 1 &  2, the tracker will stop prior to reaching the switch.
This might be used to save wear on the mechanical switch.

SoftLimitsAL

Outside the HARD LIMIT SWITCH MIN, the tracker will stop when it encounters the mechanical switch. This is selected when Auto Cal is in use or as a backup to the switch.

Mechanical or Proximity Limit Switches are wired to the controller and provide physical limits to the tracker’s travel. These should be located at the furthest point the Tracker should ever travel. The Tracker IPm will operate without limit switches but it is not recommended.

You should always use mechanical limit  or proximity switches to prevent over travel which could cause personal injury, damage the tracker or to nearby structures.

Test Limit Switches thoroughly prior to putting the tracker into service.

For increase accuracy and reliability, when Auto Cal is selected for each axis, the controller will re zero itself each time it touches the minimum limits. It is important to always  set the soft limit outside the mechanical switch position. Read more more on configuring Auto Cal …

 Night Stowage Setting moves the tracker to a pre-set position at sunset. If the position is outside either the soft or mechanical limits, the tracker will stop at the limit it encounters first and never reach the configured stowage position. Read more on configuring Night Stowage …

 

Continue on Tab F IN

F-IN-limit1

Click for enlarged view

See Figure below.  Arrows indicate “Required Information” Disregard I/O Tag Names beginning with AZI for Single Axis or Parabolic Trough.

Next Step:  Sunset Storage Position