The LabJack U12 is a versatile, precise, and inexpensive interface. It provides 12-bit analog input precision and both analog and digital outputs and connects to the computer via USB.
The LabJack cannot directly control the common Yaesu G-5400 and G5500 rotators, but adding a simple transistor interface (such as the LabJack PiggyBack) is an easy job.
Eight analog inputs, four digital outputs, and two analog outputs are available at screw terminals on the top of the LabJack case. Additional digital outputs are presented at a DB-25 female connector. The LabJack connects to the computer via a supplied USB cable. It needs no external power supply. Windows recognizes the LabJack as soon as it is plugged in; no setup is required.
Up to five LabJacks may be connected to Nova. This allows use of a separate LabJack (with its associated calibration settings and channel assignments) for multiple satellite systems.
Nova allows considerable flexibility in assigning LabJack channels to various functions. Below are the default assignments. The defaults are appropriate for the Yaesu 5400/500 rotators.
|Yaesu DIN plug||Function||LabJack
|6||Az position||AI0-AI1 (differential)|
|1||El position||AI2-AI3 (differential)|
The basic functions of LabJack are configured identically to those of other antenna control interfaces in Nova. Up to five LabJacks can be configured independently in Nova. If more than one LabJack is present, the Select LabJack drop-down box is enabled to select among them.
Advanced features, described below, are accessed through the Advanced LabJack configuration button. All advanced settings apply to the currently-selected LabJack.
Input config selects whether the analog input is configured single-ended (the default) or differentially. Single-ended is referenced to ground. In other words, the Azimuth voltage-sensing line would be connected to AI0 and the Elevation line would be connected to AI4. Note that the range for input is +/-10 volts. When using the Yaesu rotators, whose total range is 0-5 volts, only ¼ of the LabJack's potential resolution is being used. This loss of precision is unimportant because the Yaesu potentiometers have rather poor linearity.
Differential is measured between pairs of inputs. The advantage of differential inputs is greater use of the 0-5 Volt range of the Yaesu rotators. Differential operation allows selection of internal gain which maximizes the available precision. For use with Yaesu rotators, select +/- 5 V. When Differential is selected, a different set of channel selection options is presented. Note that channels are selected in pairs. It is permissible to connect one channel to ground so that operation is pseudo-differential. In the example to the right, AI1 could be connected to ground and sensing voltage connected to AI0. Please read the LabJack documentation for complete information.
Output channels are assigned from drop-down boxes. Note that the channels designated IO are available easily through the screw terminals on the top of the LabJack case whereas those with D prefix are accessible only through the DB-25 connector.
Normally, the LabJack digital output channels are set high (+5V) when on. Reverse polarity provides the opposite so that high = off.
Enable analog output, if checked, provides analog voltage at terminals AO0 (azimuth) and AO1 (elevation). The voltage ranges between 0-5 volts and is proportional to the difference between the current antenna position and the satellite target position. When the antennas are on-target, the voltage is nearly zero. Analog output could be used to drive proportionally-controlled rotators whose speed varies with angular error. Alternatively, one could display the error on a 0-5V panel meter. All LabJack functions remain operational whether analog output is enabled or not.
Although the Yaesu rotators do not have mechanical brakes, many other rotators do. Selecting Azimuth and/or Elevation in the Brakes page will enable brake control lines. Note: Because only four digital I/O lines are available at the U12's case-top screw terminals, it is possible to inadvertently assign a brake channel to a rotator-control channel. Be careful not to do this. If rotator-control channels are assigned to IO0-IO3, then the brake(s) must be assigned to one (or two) of the DB25 pins.
The brakes are disengaged immediately before initiating azimuth or elevation rotation. They do not engage immediately after stopping, however. A variable delay may be selected for each brake. This delay occurs before the brake is engaged so the antenna can coast to a stop.
Leave Az (or El) brake ON when quitting sets whether Nova toggles the brake lines when quitting. If you leave the brake on, then manually moving the rotators can be difficult without unplugging the LabJack. Un-checking these boxes sets the brake lines off when Nova closes.
Reverse polarity swaps the polarity of only the brake lines. These are treated separately from the antenna-control digital outputs because you may want the brake OFF when the rotator motors are ON. When un-checked, on=high, off=low. When checked, on=low and off =high.
The Utilities page provides information about the selected LabJack. Change local ID allow you to re-enumerate the selected LabJack. This makes sense only if more than one LabJack is connected. The Local ID is used by Nova to identify the individual LabJacks. Reset LabJack resets and then re-enumerates the device, something that should seldom (if ever) be necessary. Driver version is the version number of ljackuw.DLL, the driver provided by LabJack. Firmware version describes the EPROM firmware inside the LabJack. Serial number is a permanent unique number associated with each LabJack.
The Reset button acts independentlly for each page. Here are the default settings for use with the LabJack PiggyBack.