Optically-isolated relays inherently have a long lifespan, thanks to their lack of moving parts and the robustness of their solid state electronics. You can, however, make them last even longer by accounting for LED power losses.
Keep in mind that LED power does not remain constant over time. Instead, all LEDs experience a power loss in proportion to the time that current is applied to them. With optically-isolated relays, including PhotoMOS, this loss of LED power affects the device’s operating characteristics and lifecycle.
Rising Currents. As LED power falls, the relay’s operating currents will rise accordingly. On a typical PhotoMOS relay, for example, LED power might drop by roughly 3% after a 5 mA input current has been applied for 100,000 hours. As a result, the relay’s operating (IFon) and turn off (IFoff) currents would rise from their initial value by 3%.
This change in the electrical characteristics of the PhotoMOS has lifecycle implications. As LED sensitivity degrades with continues usage, more current is needed to generate the same amount of light. This light is used to charge the gates of internal MOSFETs and ultimately turn the relay on.
Slower Turn On Time. The turn on time of optically-isolated relays slows as LED power falls. Going back to our example of a 3% degradation of LED power after 100,000 hours at 5mA, the turn-on time would likewise slow down by 3%. Put differently, a PhotoMOS with a turn-on time of 0.03mS out of the box will have a turn-on time of 0.0309 mS after 100,000 hours of use at 5 mA.
This slowdown occurs because light intensity diminishes, which reduces the voltage and current output of the photo diode array in the IC. So it takes more time to bias the MOSFET gates.
Elevated Temperature Effects. At elevated ambient temperatures, more LED current is needed to generate the same amount of lamination. This lamination will then be converted to produce the necessary electrical voltage and current to charge the gates of MOSFETs and maintain ON state.
Careful design is required to set up the series limiting resistance of the input LED to ensure proper operation of the relay across the operating range of the relay.
Design Takeaway
In many applications, the electrical change related to optically-isolated relays may not make a practical difference. Adding 3% to an already fast on-time, for instance, won’t matter in every application.
Yet even incremental changes in performance or lifecycle can be significant in cutting edge applications. Examples include high-speed test and measurement systems.
In these cases, the datasheet alone won’t tell you whether you have picked the right relay for the job. You will have to evaluate the relay based on the electrical characteristics that will emerge after an operating time horizon that corresponds to your application.
For more information on how LED power losses will affect your application, contact Aiman Kiwan.
Panasonic’s 3D Sensor Camera
As interactive signage and immersive multimedia installations become more widespread, they have driven a need for advanced 3D imaging devices that can track gestures and other human movements under challenging lighting conditions. Our D-IMager sensor camera is a prime example.
This time-of-flight (ToF) imaging device combines 3D distance measurement with a patented background light suppression technology. It senses gestures and movement in lighting conditions ranging from total darkness to bright sunlight. And its ability to process data pixel by pixel enables accurate motion capture and recognition of spatial objects.
Here’s a closer look at how the D-IMager works and what it can do.
Operating Principles
D-IMager consists of a LED block, a proprietary CCD imaging sensor and an ASIC. It works by emitting light from the LED block and calculating the time it takes for that light to reflect back from people or objects in its field of view (FoV). Complex computer algorithms crunch all the distance data.
The ASIC, meanwhile, performs the patented background light separation operation, separating ambient light from the light reflected by the target on a pixel-by-pixel basis.
The D-IMager processes the image data in pixels as raw depth data map. The image data, which is 16 bits long, is extrapolated as polar coordinates. This raw data map then needs to be converted to spatial cartesian coordinates via readily available software development kits (SDK).
The SDKs typically handle the cartesian conversion in a graphical way that makes it possible to create gesture control and body tracking applications. For example, raw data can be converted into skeletal models and displayed as avatars.
What it Can Do
Currently, three different D-IMagers are available—Models 3104, 3105 and 3106. All three have some common characteristics, but they differ in some key regards:
- Lighting Requirements. The original D-IMager, Model 3104, serves in lighting conditions up to 20,000 lux. So does the Model 3105, though it has a higher sensitivity than than 3104. Model 3106 addresses high illumination applications—up to approximately 100,000 lux. To date, the 3106 is the only commercially available IR ToF sensor that can be used with such high illumination levels.
- Pixel Format. All D-IMagers have a nominal pixel format of 160 x120. They have a minimum measurement range of 1.2 meters. Maximum measurement range is 9 meters for Models 3104 and 3106. Model 3105 has a maximum range of 5 meters.
- Frame Rate. All three models offer frame rates of 15, 20, 25 and 30 fps.
- Field of View. The further the target is away from the camera the greater field of view (FoV) angle and the lower the resolution. In most applications, FoV above 60 degrees can easily be balanced with the resolution needed for gesture or movement tracking applications.
Important Applications
Whenever an interactive system requires a display to react to human movement, the D-IMager sensor camera can be a key enabling technology.
Applications that this 3D movement sensor has helped to date include interactive informational kiosks, digital mirrors, interactive museums displays, traffic tracking systems for stadiums, augmented reality systems, hospital operating room x-ray imagers, interactive CAD software, immersive multimedia systems, interactive digital signs and more.
Check back soon for more posts on D-IMager or contact Dario Torres for additional information.
As solar farms and energy storage systems grow in scale, they increasingly require power relays that can safely cut off high DC voltages. That’s where our new HE-V relay comes in.
Designed specifically for alternative energy applications, this new 2 Form A power relay provides:
- Outstanding capacity. A nominal voltage of 800 VDC and maximum switching capacity of 1000 VDC, 20 A has been achieved at each of the HE-V relay’s 1 Form A contacts. These contacts are connected in series to allow the simultaneous cutoff of DC positive and negative terminals.
- Reduced energy requirements. HE-V relay contributes to energy saving in devices thanks to a coil hold voltage that is just 33% of the nominal coil voltage. Nominal operating power is also low at 210mW.
HE-V APPLICATIONS.
The HE-V relay can be used in a variety of DC power applications—including photovoltaic power generation, energy storage, inverter control and DC load control.
- In solar applications, one or more HE-V relays can disconnect individual solar panels or strings of panels. Reasons for cutting of panels include maintenance, emergency response and bypassing panels with efficiecy problems. (See Figure 1)
- In energy storage applications, HE-V can protect against high inrush currents during the charging of capacitors or storage batteries.
For more information on HE-V, contact Mamitha Mathew.
GT Series HMI
Is your GT series HMI in a public area or used by multiple site personnel? While leaving HMI programs open to your entire staff is the easiest route to take, it is also the most dangerous. Allowing access to high level functions and settings which require expert knowledge and experience, to all personnel is ill-advised and has the potential to interrupt and/or delay production. With the GTWIN operation security features, setting access and permission levels is easy.
Panasonic has included operation security settings on the GT05 and GT32 for some time and it is now available to all USB enabled HMI. When activated, operation security allows you to assign passwords and various levels of security to GT parts.
There are 16 security levels available, (0 through 15). Level 0 requires no password. Access to any level grants the user access to that level and all levels below. For example, an assembly line worker with level 3 access, can see and operate all devices with level 3, 2, 1, and 0 security. Supervisors with level 6 access, can see and operate all devices with level 6 and below security.
Panasonic’s operation security settings allow up to 64 accounts with individual passwords, enabling multiple registrations per level. Shown below are screenshots of the the Operation Security Dialog boxes.
