Radio Frequency Test Stands for Remote Controllers
- 1. Radio Frequency Test Stands for Remote Controllers by Sundaram Raghuraman, Lorne Repas, Wei Tung, Kripa Nidhi, Ujjal Dutt, Anthony Young, John Field, Ryan Hess, Anthony Sahm Team Leader, District Manager, Sr. Project Engineer, Sr. Project Engineer, Project Engineer, Co-op, Co-op, Co-op, Project Engineer VI Engineering Category: Telecom Products Used: PCI-6023E, PCI-6024E, PCI-MIO-16XE-10 PCI-1408 SCC-2345 PCI-DIO-32HS PC-ER-16 PC-DIO-24PNP PCI-GPIB-TNT LabVIEW™ 5.1 LabVIEW Test Executive 5.1 LabVIEW SQL Toolkit IMAQ™ Vision The Challenge: The objective was to develop four test stands for production testing of Radio Frequency (RF) remote control components. The main challenges were: • Complexity of the UUTs and test requirements. • Both test stand and product development were in parallel necessitating close co-ordination between both teams. • Management of the project with a large team, several pieces of both custom and standard equipment. The Solution: By using LabVIEW and LabVIEW Test Executive we were able to rapidly develop the software by concentrating on individual tests instead of the test sequencing architecture, user interface etc. Introduction The UUTs tested were transmitter PCB, receiver PCB, receiver assembly, and transmitter assembly. Some tests required an anechoic RF chamber to exclude RF interferences. Several instruments were used in the test stand (RF signal generator, RF spectrum analyzer, power supplies, digital volt meters, pressure transmitters, optical encoders) and were controlled by the computers using GPIB or RS-232 communication. In addition, the stands required relay control for activating solenoids and switches and this was accomplished using PC-ER16 relay devices. Digital I/O cards were used to read/write EEPROM data in the receiver and transmitter PCBs. All stands included bed-of-nails fixtures or clamping fixtures for mounting the UUT and providing access to the electrical input points and test points on the UUT. The transmitter assembly test stand used IMAQ Vision software, and IMAQ hardware and cameras for testing LCD screen on the UUT. Requirements Some important requirements for all test stands were ease of use, automatic test sequencing, user-configurable test sequence, test limits, test parameters, and test branching, user-configurable multiple security levels with corresponding function levels, self-diagnostics, user-configurable maintenance scheduling/monitoring/logging. In addition each test stand had its own test requirements. Project Management and Software Design Project management was important because of the strict deadlines, short development period, design changes, involvement of a large team of people, and multitude of custom and standard hardware from several vendors.
- 2. Therefore VI Engineering (VIE) developed a comprehensive project plan outlining all major software tasks, hardware delivery dates, resources and deadlines and created a project schedule based on their dependencies. VIE created a design document and a software architecture document for each of the test stands. The design document defined the test sequence and individual tests for each test stand. It served as a scope of work document and was provided to the customer. The software architecture document described the test sequence and tests in more detail. It served as a developer’s reference document and was provided to the VIE’s project team. It identified test VIs, test sub-VIs and common sub-VIs to be created, and driver sub-VIs to be used. It defined the terminology and software conventions to be used so that all the team members could create software in a consistent manner. The choice to use LabVIEW Test Executive was an obvious one as it satisfied many of the requirements. Although NI’s Test Stand is more powerful, we selected Test Executive because it was easily customizable. We enhanced the Test Executive with several new features such as user-configurable security and function levels, user-configurable test parameters, preventive maintenance scheduling and logging, enhanced test report and error messaging capabilities, and diagnostics. Figure 1 shows the Test Executive operator interface screen. Figure 1. Test Executive Operator Interface. For each test stand, the test sequence was broken down to a series of tests which were developed as individual LabVIEW test VIs. These LabVIEW test VIs were created using VIE’s state queue software architecture. This was done by first breaking down each test into a series of steps, and then assigning each step to a state in the state queue. Additional steps were created for pre-test and post-test operations and were integrated into the state queue. Additional LabVIEW VIs were created for pre-UUT, post-UUT, pre-UUT-Loop, and post-UUT-Loop operations and integrated into the test sequence. A typical test sequence is as follows: • The operator scans the UUT using the barcode scanner to read in the UUT’s ID. • The software checks the main database to see if the UUT has passed all previous up-stream test stands. • The operator places the UUT in its fixture and closes the door of the chamber. A switch on the chamber’s door initiates the automatic test sequence. • The software then proceeds through the test sequence by controlling instruments. • The software displays the PASS or FAIL banner to the operator.
- 3. Transmitter PCB Test Stand The test stand was designed to perform a test sequence of 6 tests. The main components of the transmitter PCB test stand are shown in Figure 2. The main purpose of the test stand was to verify components and functions of the transmitter PCB. The transmitter PCB is powered by the power supply, and electrical contacts are controlled by relays. By controlling the electrical contacts, the transmitter PCB is operated in factory test mode, where it transmits RF messages. The RF transmission is received by the patch antenna and demodulated and analyzed by the spectrum analyzer. There were tests to verify RF carrier strength and frequency, demodulated signal frequency and duty cycle etc. At the end of the test, data is written to the transmitter PCB’s EEPROM using digital outputs. RACK DELL Monitor P780 Keyboard, Mouse DELL Computer Optiplex GX1 PC-DI0-24 PCI-GPIB PCI-DIO-32HS Barcode Scanner Wiring Cabinet NI SCB-68 NI PC-ER-16 Bed of Nails Fixture Transmitter PCB ANECHOIC RF CHAMBER Cable for Data & Control HP Power Supply E3631A HP Spectrum Analyzer E4411B Antenna RF Signal RF Signal Cable Power Cable Figure 2. Schematic layout of the transmitter PCB test stand. Receiver PCB Test Stand The test stand used was designed to perform a test sequence of 12 tests. The main components of the receiver PCB test stand are shown in Figure 3. The purpose of the test stand was to verify various sub-assemblies and components and also specific functions of the receiver PCB. The receiver PCB is powered by the power supplies. The signal generator sends RF commands via the patch antenna to the receiver PCB to perform required tests. The data from the receiver PCB’s EEPROM were read by the optical encoder. There were tests to verify power up time, power up voltage, motor circuit, fan circuit, error codes, RF sensitivity, shut-down time etc.
- 4. RACK Dell Monitor P780 DELL Computer Optiplex GX1 PC-DI0-24 PCI-GPIB PCI-6023E Barcode Scanner Wiring Cabinet NI SCB-68 NI PC-ER-16 HP Power Supply E3631A HP Signal Generator 8648A Bed of Nails Fixture Receiver PCB Antenna RF Signal ANECHOIC RF CHAMBER RF Signal Cable Cable for Data & Control HP Power Supply E3631A HP Digital Volt Meter 34401A Variac Power Cable Keyboard, Mouse Figure 3. Schematic layout of the receiver PCB test stand. Receiver Assembly Test Stand The test stand used was designed to perform a test sequence of 2 tests. The main components of the receiver assembly test stand are shown in Figure 4. The purpose of the test stand was to both calibrate the receiver assembly and perform an operation check. The signal generator was used to send RF commands to the receiver assembly and used to control its operation. The receiver assembly valve motor was calibrated for different pressure levels by stepping it from high to low pressure. The software then performs an op-check by verifying that the receiver assembly reaches the correct pressure level for each calibrated position.
- 5. RACK Dell Monitor P780 DELL Computer Optiplex GX1 PC-DI0-24 PCI-GPIB PCI-MIO-16XE10 Barcode Scanner Wiring Cabinet NI SCB-68 NI CB-50LP HP Power Supply E3631A HP Signal Generator 8648A Clamping Fixture Receiver Assembly Antenna RF Signal ANECHOIC RF CHAMBER RF Signal Cable Cable for Data & Control HP Power Supply E3631A Power Cable Keyboard, Mouse Figure 4. Schematic layout of the receiver assembly test stand. Transmitter Assembly Test Stand The test stand was designed to perform a test sequence of 10 tests. The main components of the transmitter assembly test stand are shown in Figure 5. The purpose of the test stand was to verify the operation and image quality of the LCD screen on the transmitter assembly. The image on the LCD screen was acquired using the cameras and IMAQ hardware. The transmitter assembly was operated in several factory test modes, by pressing appropriate buttons using solenoids on the clamping fixture. There were tests to verify 7-segment LCD characters (vertical segments, 8’s, and horizontal segments) and also check for icons and patterns. In addition there were tests to verify that data was stored correctly in the EEPROM by viewing it on the LCD screen.
- 6. RACK DELL Monitor P780 Keyboard, Mouse DELL Computer Optiplex GX110 PC-DI0-24 PCI-6023E Barcode Scanner Wiring Cabinet NI SCC-2345 NI PC-ER-16 Clamping Fixture Transmitter Assembly Lamp LIGHT ENCLOSURE Cable for Data & Control Camera1 Camera2 PCI-1408 Cable for Cameras Figure 5. Schematic layout of the transmitter assembly test stand. Conclusions The RF Test Stands had more functionality, robustness, and consistency by using the Test Executive than would have been otherwise possible within the short time available. Diligent project planning and management allowed accelerated development by using a large project team. The systems were tested for repeatability, and performed as required. Acknowlegments VIE would like to acknowledge the many suggestions and contributions made to the systems by Robert Zak, Brent Chiang, Bruce Hill of Honeywell Inc. We would also like to thank Stan Case of VI Engineering for the most of the features of the enhanced Test Executive.