Automated Production Testing
Reasons for Customised Testing
General purpose test equipment often fails to meet the requirements for individual products. This is particularly true where analog sensing and outputs are involved.
Another issue is licensing of run time executives where there are additional license costs for each instantiation of a tester.
Yet another factor is the time frame for producing the test scripts and debugging them. The structure of the test language can also complicate some simple tasks such as calibration or loop back testing where a test is rerun and a recalibration is done until a unit is in specification. This is sometimes required where a purely mathematical calibration equation is not available. eg. automating the setting of a trim pot.
To solve the above issue most systems then require development of custom Windows DLLs to add to the functionality of the underlying test language.
A number of our clients have run into the same issue so we have been producing automated testing stations for them. These stations have the following capability:
- can be controlled by any Windows version from Win98 up
- USB or Serial port connection. A single cable connection allows easy swap out of a PC.
- standard industrial control PCB based on Atmel ATmega128. This provides 8 Digital inputs, 8 Digital outputs, 3xRS232, 1xRS485, 1x1 wire bus and 4 analog inputs.
- multiple stations can be run from a single PC
- test script execution happens across the stations so time delays are in parallel rather than serial. This saves a lot of time compared to sequential testing processes where the delays are in series.
- an entire panel of PCBs can be tested together as a panel
- selection of individual fixtures in a multi fixture set for retest
- direct programming of Atmel AVR devices via an AVRISP connected to an RS232 port on the industrial controller
- calibration constants can be written directly in EEPROM as can a unique serial number and even test date and batch information
- automated serial number generation
- scripting to allow customisation of the test process - no need to rewrite the main application to vary a parameter
- scripting also allows testing of subsets of the protocol - eg. for service support
- on screen RED/GREEN light outcome as well as logging of all test processes
- use of an external LCD for displaying test results where a CRT or LCD monitor would adversely affect the test - eg. magnetic sensing systems
- all script, setup and results files are human readable and editable in any standard text editor
- can export reports in other formats as required
At present we have specialised in Atmel AVR devices but our technology could easily accommodate other processor families.
Software Costs and Licensing
Our experience to date has shown that a complete test application can be developed for a budget similar to the purchase of just the developer suite toolset for most of the mainstream automated test solutions. This includes any customised code in the industrial controller as well as the main PC application which is developed using Borland's C++ Builder toolset and a number of third party add-ons.
Most clients prefer to pay a single cost and then have the right to make as many duplicate test stations as they need.
In addition to the Software costs are the actual hardware costs associated with the fixtures and the industrial controller. These include:
- industrial controller and interfaces $600+GST
- AVRISP programmer $60+GST
- USB to 1 RS232 port $80+GST (if the PC serial port is already used)
- USB to 4 serial ports $300+GST (can run multiple fixtures from 1 PC)
- custom fixture hardware and power - this varies according to need. We can make it or our clients can make it to our specification.
- fixture mechanics - one client does pressure testing with air and water. We can accommodate your requirements.
- external LCD display - also varied by need. A common approach is to use a pocket PC or a terminal emulator LCD product to minimise cost.
Re-use of Existing Facilities
Where existing hardware is available this can be used as part of the process. We do not require a clean installation where we supply everything so your existing investment is not at risk.
The last test system we put together required about six weeks for the application development. The client built the mechanical and electrical fixtures in parallel with this and commissioning happened immediately afterward. So long lead times are not the norm and this is reflected in the relatively low development and implementation costs.
The standard pricing is based on the following:
- all fixture drawings can be freely used
- industrial controller source code and PC source code remains our property
- executables can be freely used and distributed
If you want to have access to the source code for your own internal use only, we can discuss pricing for that as well but it has been a substantial investment and we don't expect any one client to want to have to pay for it on their own.
An OEM supplier of controls and intelligent accessories to the white goods industry is using this system to test and calibrate their product in production runs which vary from 1000 to 5000 devices at a time. This replaces a facility based on one of the standard testing products. The flexibility of use, easy changeover of the PC (doesn't need to be dedicated to 1 job) and the ability to easily extend it to include product variants and the quick time to test is expected to save money in both the cost of getting a new rig together and also the cost of the testing itself. The ability to customise the scripts locally also saves on maintenance and extension costs. It also allows tweaking to cope with production batch variations without having to call in a third party to change the tester's operation. And the closed loop calibration facility where the calibration data is written directly to the EEPROM by the test facility also saves time and reduces the likelihood of operator error.
All of this and they don't need a programmer dedicated to production (or in their case even on staff) to support it.
Interested in Knowing More?
We would be pleased to review your requirements and offer you a solution to your current testing needs. We can also offer a comprehensive product design, development and production test service. Contact us for a quote on your next project.