As we mentioned in the last post, the new DiscoFridge design includes an Arduino single-board microcontroller. The x86 controller board we’re using is designed for building small form-factor PCs, which typically don’t have a GPIO interface. Because DiscoFridge will need to control valves, interpret pulse trains generated by the flow meters, control LEDs, interface to a dollar bill reader, etc., we need a way to talk to these hardware peripherals. We decided that an Arduino microcontroller such as the Uno or the Pro Mini would be a cheap and easy way to talk to hardware peripherals, and we happen to have one sitting around. (Actually about 5; these things are awesome!)
The Internet of Things (IoT) is hardly a new concept; the term has been around since 1999, and the objects themselves have been in development even longer. IoT objects are usually described as “uniquely identified objects with embedded technology to communicate with each other and the internet”, and there are already over 10 billion in use today. While IoT connectivity is standard for computing devices, in the next few years the network will expand to…well, everything. By 2020, experts predict:
- There will be over 50 billion connected things
- Every product that costs more than $100 will be smart
- The IoT will add $1.9 trillion in economic value Read More
Earlier in this series we discussed why design validation testing (DVT) is important, and how Environmental DVT is performed. Now we’ll take a look at Mechanical and Reliability DVT, and how electronic product designers ensure that their customers always receive the product in full working order.
The objective of mechanical DVT is to verify the integrity of the mechanical design and product assembly under various use cases. Mechanical DVT will usually contain drop tests, vibration, and shock impacts testing.
A drop test verifies that the product will survive mishandling situations. A realistic scenario is where the product is dropped on to a hard surface such as hardwood floor, tile, or a concrete surface, and is best replicated using a free fall drop testing method. In the free fall drop test the product will be dropped from a recommended height based on its overall weight onto a hard surface (e.g. concrete) on all its faces and edges.
Random vibration testing, as the name suggests, simulates vibrations that are found in everyday life that are neither repetitive nor predictable. The goal of vibration testing is to uncover weaknesses in the mechanical design as a result of the environment it may encounter. This type of design validation testing will provide data points for improvement. During vibration testing a product is tested independently on each of its three orthogonal axes while operational. The vibration levels and frequency range is dependent on the target application for the product. Read More
“Gratitude is a quality similar to electricity: it must be produced and discharged and used up in order to exist at all.” – William Faulkner.
We have so much to be grateful for. Best wishes for a wonderful and relaxing Thanksgiving to our families, friends, clients and partners.
In our previous post we discussed why design validation testing (DVT) is so important for electronic product designs, and described how electronic and electromagnetic tests were performed. Next we’ll take a look at environmental DVT and how it can ensure the reliability of an electronic product in all conditions.
The objective of environmental DVT is to verify that a prototype design satisfies product requirements for various environmental operating conditions such as temperature, humidity, altitude, water and dust exposures. Consumer electronics are not usually expected to withstand extreme conditions, but products for applications such as military or aerospace will have a much wider operating range.
Temperature testing (or Thermal Cycling) validates product operation within specified operational temperature limits. Humidity testing can be phased in with the operational temperature tests so that all conditions can be represented. The duration of thermal testing will vary depending on the application, and can range from a few hours to many days. The figure below shows a thermal cycle profile for a product used in an industrial environment. In this case the product was tested between 0°C to 50°C 70±5% RH for duration of approximately 3 days.
Temperature tests can also include scenarios where the product is not expected to be operational, such as storage environments, or situations where the product has been exposed to cold and hot temperature conditions for an extended period of time (e.g., left in a car during hot and humid or sub-zero conditions). For these test conditions a product undergoes a cold and a hot temperature soak for an extended period of time, and is then powered up to verify correct operation. Read More
GPS has become nearly ubiquitous in all autonomous designs; even so, GPS is rarely used as the sole sensor for navigation. This section outlines some of the limitations of GPS systems and how they can be overcome by combining GPS with other technologies. (Catch up on Part 1 and Part 2 of our GPS design series if you missed them.)
One of the main limitations of GPS, and a continuing issue for autonomous design, is accuracy. Even though high-end systems can provide centimeter-level precision, these systems are cost-prohibitive for most hobby and commercial applications. Most cost-effective GPS receivers provide GPS and GLONASS support with WAAS capability. These receivers can, at best, provide precision to about three meters.
Receiver Accuracy Specification
When selecting a GPS receiver it is important to understand how receiver accuracy is specified by the manufacturer. Most accuracy tests are performed by the manufacturer in ideal conditions. Typically, the spec assumes little or no multi-path interference, and an open sky with at least five visible satellites. Therefore the specification will be a best-case scenario and should not be regarded as a typical measurement. It is also important to note that in many instances only the horizontal position accuracy is quoted; the altitude accuracy can be up to 2-3 times worse.
GPS accuracy is specified in terms of the probability that a particular measurement will be within a certain radius. In many cases the manufacturer specifies receiver accuracy as the Circular Error Probable (CEP).
Circular Error Probable (CEP)
The CEP is a statistic that specifies the radius of the circle that will contain approximately 50% of all position measurements. Furthermore, 95% of all measurements will be within twice the radius and 98.9% within 2.55 the radius.
As an example, for a particular receiver with a CEP of 3 meters, 50% of all measurements will be within 3 meters of the true position, while 95% will be within 6 meters, 98.9% within 7.65 meters, and the rest will be further out, as shown in the image on the right. Note that since consecutive measurements can fall anywhere in the circle, the difference between two consecutive measurements can be over 15 meters in the worst case, and can consistently exceed 6 meters. As can be seen, the 3 meter accuracy specification can be far from reality in a real-world application. Read More
After emailing with Steve and talking to him on the phone for quite some time, I was glad to finally corner him for a proper real-life meeting during a recent trip to the Waterloo Design Center. After a good chat about education (he’s basically a self-taught design guru), our childhoods (his parents were missionaries and he grew up in India!), and life in general, we got down to business with the interview. Read More
The worst fear of any electronic product company is that serious design issues will be uncovered after the product has shipped in volume. In 2010 the world experienced “Antennagate” when Apple customers reported dropped calls and poor reception with the iPhone 4. A class-action lawsuit was filed, and the settlement resulted in over 21 million people in the US being eligible for $15 or a free case from Apple. These scenarios are embarrassing for an electronic product company at best, and at worst can have irreparable financial repercussions.
The surest way to prevent a debacle like this is with thorough design validation testing (DVT). DVT is a method of testing products to verify that a product satisfies all of its design specifications. After production begins, DVT is required again if there are component substitutions due to second-sourcing or component obsolescence, to ensure that none of the design specifications has been compromised.
Design validation covers various aspects of a product design and can be categorized as follows:
- Electronic DVT
- Electromagnetic Compatibility DVT
- Environmental DVT
- Mechanical DVT
- Reliability DVT
- Transportation DVT
With Electronic DVT the product design is broken into various subsystems, and tests are created to validate each one. Subsystems in a typical electronic product design could include power supplies, clock and reset, memory, Video, USB, Ethernet, Bluetooth and Wi-Fi.
Our engineers are always up to something interesting, whether it’s designing a kegerator, building a flamethrowing fish, or doing astrophotography. Here, Lead Design Engineer George Reimer shares his latest after-hours project, a first person video (FPV) head tracking system.
I, like so many others, have been enthralled with the FPV activities by friend and colleague, Trevor Smouter here at Nuvation. A little while ago he invited me to his aircraft flight simulation laboratory to take the controls of a Bell 202 helicopter. The simulator he used was Microsoft’s Flight Simulator X projected onto the wall in 3D. I have flown flight simulators for a number of years, including ones with realistic yoke and throttle controls, but the thing that really captivated me with Trevor’s setup was the head tracking; it was fantastic! It really pushes the experience over the edge to make you feel like you’re really participating in the adventure.
I felt the need to bring this experience home. So for Christmas last year, my wife surprised herself by buying me a Nvidia 3D Vision upgrade for my desktop system at home. This was really great and I enjoyed using it, but it didn’t come cheap.
In part 1, we discussed how GPS works and some of the factors that degrade GPS accuracy. Here we take a look at how you can get around these limitations for your electronic product design.
Over the years, GPS receiver manufacturers have devised numerous algorithms and techniques resulting in significant GPS accuracy improvement using the existing GPS infrastructure. In fact, some of the advanced receivers used for land surveying are able to achieve sub-centimeter accuracy.
One of the most important techniques is called Differential GPS (DGPS). DGPS systems use a stationary GPS receiver placed at a precisely known location as a reference for other stationary or mobile GPS receivers. The idea is that two receivers sufficiently close to each other will receive GPS signals that travel through nearly identical slices of the atmosphere. By knowing the precise location of a receiver, the error introduced by the atmosphere can be computed. This error is then relayed to other receivers in the area that can then compensate for the error in their measurements.