About the reliability of our devices
We have been developing and manufacturing electronics for automation and monitoring since 2012. We specialize in developing industrial Linux-based controllers, as well as Modbus-interface peripheral devices: universal sensors, relay modules, lighting dimmers, multichannel meters, analog input blocks, etc.
Over the years, we have released eight generations of Wiren Board controllers and several generations of peripheral devices. We have helped our partners automate tens of thousands of sites and accumulated extensive experience in developing, testing, and deploying equipment.
Our equipment is used in various projects, from automated apartments to greenhouses, weather stations, and other facilities. Therefore, the requirements for our equipment are higher than for consumer electronics.
In this article, we will talk about which factors affect equipment reliability and what we do to ensure our devices please their owners with unpretentious and long-lasting operation.
Every device we manufacture undergoes a mandatory
automated check before being sent to the customer
Circuit Design
When developing new devices, we try to use only proven circuit solutions that already work successfully in our other products.
But when designing and producing equipment that is fundamentally new for us—for example, an HMI panel—we have to experiment, as much of it is a first for us:
- a new enclosure,
- components that are new to us—a liquid crystal display and a sensor,
- a new control interface,
- new solutions for component layout on the board,
- new production and testing standards, and unknown potential issues.
Despite thorough testing and refinement of a new product before release, the first users will still act as beta testers. And we will learn from their feedback and make our devices better.
Component Quality
Counterfeits are often sold on the electronic components market: remarked parts with worse characteristics or chips from no-name manufacturers that enterprising sellers rebrand as well-known brands.
We try to address the issue of counterfeits by working with official distributors and trusted suppliers.
For example, we encountered a mass failure of AM2320 temperature and humidity sensors—about 20% of the sensors failed after a year of operation. To solve the problem, we switched to another sensor model from a different manufacturer—HDC1080. The new sensor cost more, but defects became isolated cases.
On another occasion, we purchased a large batch of MAX485 transceivers that turned out to be counterfeits of a well-known brand and did not meet the “A/B line short-circuit current” parameter.
Due to the controller’s circuit features—a powerful power supply and self-resetting fuses on lines A and B—this led to transceiver failure with the case melting. Moreover, the effect did not appear in peripheral devices because their circuitry was different. We reworked the controllers, discarded the remaining parts, and switched to another transceiver model purchased from an official distributor—this solved the counterfeiting issue; MAX485 is very popular and therefore often counterfeited.
Assembly Quality
All assembly operations are regulated by instructions, and assemblers undergo training and briefings.
When a batch is launched, it is assigned a number and a batch card is created.
We record every operation performed: who did it, when, and how long it took. We also carry out visual inspections at separate stages: SC—soldering of SMD components; VC—soldering of through-hole components; QC—appearance.
Each device with a microcontroller also has a unique serial number. This allows us, when problems are detected, to understand which other devices may be affected, notify customers, and arrange returns if necessary.
Functional verification (testing) is automated for almost all devices. During testing, the operation of inputs/outputs is checked, sensor measurements are compared against a reference, the device’s current consumption is measured, etc. Test results are stored in a database. If a device does not meet the specified test parameters, it is sent to the repair department to determine the causes. Analysis of test data also allows us to identify problems with purchased components, consumables, and bottlenecks in the assembly technology.
The photo below shows the documents that regulate assembly, testing, and the transfer of devices from production to the warehouse:
- assembly diagram for through-hole mounting,
- a table comparing actual time spent with estimated time for each operation,
- bill of materials (BOM),
- batch card,
- operator’s manual for automated final testing,
- checklist for transferring the device to the warehouse.
Documents regulating assembly, testing, and transfer of devices
from production to the warehouse
WB-MAI11 test bench: the device measures reference resistances and voltages
Test bench for WB-MR relay modules
Test bench for WB-MSW3 sensors: all sensor parameters are checked automatically
in any configuration
External Influences
Two types of external influence are relevant for panel automation—overheating and overvoltage at the device terminals.
Devices whose components are manufactured using an industrial
process handle high operating temperatures better
High Temperatures
High temperatures affect key device components: integrated circuits and electrolytic capacitors.
At elevated temperatures, component degradation accelerates: device service life is reduced by 2× for every 10°C above the recommended operating temperature.
We strive to reduce the impact of high temperatures on the stable operation of our equipment:
- We use components manufactured with industrial processes and with an industrial operating temperature range. Such ICs degrade 10× more slowly than commercial ones, but they also cost more.
- Wherever possible, instead of electrolytic capacitors we use ceramic or solid-state ones.
We also try to reduce the devices’ self-heating; to this end we:
- use energy-efficient circuit solutions: synchronous DC-DC converters, low-power ICs
- select components with a power margin during design—for example, in all our relay modules we install relays with a 1.5× current margin
- design boards with heat spreaders for hot components and good thermal distribution.
The technical solutions we apply make it possible to operate Wiren Board devices at temperatures from −40 to +75 °C, whereas most consumer devices are guaranteed to operate from 0 to +55 °C.
Overvoltage at the Device Terminals
All inputs and outputs of our devices are protected against electrostatic discharge (ESD).
In addition, most inputs and outputs are protected against the application of DC voltage up to 24 V and higher, and therefore can tolerate miswiring errors during installation.
Software
Almost every one of our devices contains a microcontroller that is controlled by software (firmware). Statistics show that the likelihood of device issues due to firmware errors is higher than due to hardware problems.
We put into series production devices with stable firmware proven by time and many users. However, newer firmware with additional functionality—and possible bugs—is available for enthusiasts.
To update the controller and our Modbus devices’ software, you don’t need
to go to the site—everything can be done remotely
or automatically
For convenient firmware updates of our Modbus devices, we wrote a utility for remote updates and added support in the bootloader. A user can manually update any of our Modbus devices individually, or all at once automatically. This is convenient—you don’t need to open the automation panel, and with remote access you don’t need to visit the site.
The controller is the heart of the automation system, and the system’s stability depends on its reliable operation, therefore:
- As the operating system we use Debian Linux, known as a reliable and stable system.
- We have built in a watchdog—hardware health monitoring with automatic device reboot—which helps avoid controller hangs due to incorrect settings.
Conclusion
Our efforts were not in vain, and we managed to achieve stable quality of the devices we produce.
Here are failure statistics within the warranty period among the devices we have manufactured and sold:
- complex devices: controllers, WB-MSW sensors, etc. — 1% (detailed statistics for Wiren Board 6);
- simple devices: relays, dimmers, etc. — 0.5%.
A small failure rate is the result of our efforts
in unification, automation, and quality control in device production
We provide a 2-year warranty on all our devices. However, whenever possible, we continue to support devices even after the warranty period ends.
If you encounter unstable operation of our devices, contact us using any convenient method listed on our website, and we will do our best to help.
It is important to understand that a controller with software is a complex system that must not be used in highly critical locations if its failure would put human life at risk or lead to major financial losses: production lines, protective automation in industry, etc.
Such systems are built using specialized (and simple) PLC controllers. But Wiren Board controllers can successfully operate at industrial sites as monitoring systems and for controlling engineering systems: lighting, heating, irrigation, etc.
The Wiren Board Team