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February 3, 2012 / Dan Ackermann

Panasonic Quick Clips: A5 Servo Notch Filter

This video demonstrates the A5 Servo’s Notch filter function which is useful for vibration suppression by eliminating harmonic frequencies.

 

Learn more about the A5 Servo on Panasonic’s site: http://pewa.panasonic.com/automation-controls/servos-and-drives/a5/

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January 24, 2012 / Aiman Kiwan pewa

On-resistance vs Output Capacitance for PhotoMOS Relays

In previous articles, we’ve shown how a PhotoMOS works, and how to optimize certain characteristics. Here we talk about the balance between  Output Capacitance  and On-resistance (C vs R).

Trade-off between On resistance and Output capacitance:

Implementing  a PhotoMOS relay is a simple task, especially in electronic circuits where the coil EMI in electromechanical relays can cause unwanted noise and false signals.   The PhotoMOS can be tuned to be suitable for different applications.  Since a MOSFET is being used to switch the output side, it is apparent that the MOSFET characteristics influence the behavior of the PhotoMOS relays.  By adding more photo-cells, the operating power can be reduced. In addition, the breakdown voltage, on-resistance and switching capacity can be changed by adjusting the design of the MOSFET.  For example, increasing the breakdown voltage requires slightly doped drain area.  However, this change will also decrease capacitance and increase on-resistance.  On the other hand, lowering the on-resistance by changing the drain area leads to higher capacity but lower breakdown voltage. So, getting the right formula is a lengthy and difficult task.

Low CxR  PhotoMOS Relays:

Low on resistance and low capacitance switches are needed to reduce signal loss and improve switching time and isolation characteristics, which are key requirements for high precision applications such as in measurement and data acquisition devices.  Since both the on-resistance and the capacitance are reduced, these devices are referred to as low CxR PhotoMOS.  These improvements in the CxR values are achieved by optimizing the layout of the MOSFET and improving the internal structure including the layout of the bonding pads, manner of wire bonding and new terminal leads.

By reducing the CxR value of the PhotoMOS relay, there is some trade off in other important values such as load voltage.  Table 1 shows a the characteristics of some typical low CxR PhotoMOS relays.

 

Table 1: List of low CxR  PhotoMOS relays

Applications for Low CxR PhotoMOS

Low CxR PhotoMOS are especially suited for measurement and data acquisition applications.  For example AQY221N3V has on resistance of 5.5W and output capacitance of 1pF, resulting in switching speed of 20ms and providing excellent isolation characteristics.  The reduced length of the internal bonding wires enable new smaller package.  The new SSOP (Shrink Small Outline Package) is 60% of the surface area of the conventional SOP (Small Outline Package).  This could translate to significant board space saving when the system requires several switches such as the case of Automatic Test Equipment (ATE).

In an ATE system, various AC and DC signals are applied to Device Under Test (DUT) where the switching speed plays a major role.  The input and output signals are monitored and the measurement is taken.  Because of the variety of signals in the test system, relays with different characteristics are needed.  Low CxR PhotoMOS with reduced on-resistance are needed for DC signals reducing signal loss while PhotoMOS with reduced capacitance are needed for AC signals providing optimized isolation.

Please describe yourtoughest design-in challenge with PhotoMOS relays in the Comments section.

January 19, 2012 / nickpana

Using Time-of-Flight Cameras for 3D Sensing

There was so much buzz this past year on various and unusual reality based applications. These included: augmented reality, virtual reality, immersive reality, haptic and domotics reality , digital-out-of-home ( DOOH), so on and so on. Enough to make your head spin!

This whole reality based phenomena can be traced back when we had simple game-consoles. These started with wired joysticks then transitioned to wired position-type sensors (ie.Wii) – where the controller senses position by its orientation and acceleration in space.

We also have been exposed to a number of different sensing technologies : laser based, infra-red based, combination of infra-red and laser, laser and RGB, optical sensors, etc.  Some of these have found their way in both consumer and commercial use. Take gaming as example. Microsoft’s Kinect is quite popular today in the gaming space, reported to be in the billions of dollars.

Non-gaming markets, like hospitality, entertainment, retail, airports, interactive kiosks etc all have been reported also showing double digits growth…all way to 2015!

Let’s look at Time-of-flight (TOF) based sensors. TOF is one of the simplest and oldest technologies around.  Many instruments today use this sensing technique in spectrometry devices, ultrasonic flow meters, optical flow meters….even gesture control devices.

The concept of TOF is pretty simple. A TOF based camera emits an infra-red light ( like a TV controller), hitting a target. The light then bounces back to the sensor which then calculates the distance that it took to travel back and forth. Bingo!

Pixaleted image output from Panasonic D-IMager

Pixaleted image output from Panasonic D-IMager

The individual pixelated data produced by these infra-red lights bounce off the target and then are extrapolated ( via middleware) to produce the target’s equivalent avatar. See above.

Panasonic’s D-IMager is a good example of a TOF camera:

Panasonic D-IMager TOF

Panasonic D-IMager TOF

January 19, 2012 / Aiman Kiwan pewa

How to Speed up the Switching Time for a PhotoMOS Relay

In the last PhotoMOS blog post, we discussed how to select the correct capacitor for the application. Now we’ll move on to switching time.

Minimizing Turn-on Time

There are some cases where turn on time is crucial and the circuit designer must find ways to reduce the amount of time it takes from applying the LED forward current until the MOSFET gate is closed.  Typically, higher LED current will lead to faster switching time.  On the other hand, it will increase power consumption and reduce the LED life.  Therefore, it is ideal to initially increase the LED forward current for switching operation and then reduce it afterward.  This operation can be done using the circuit in Figure 1

Capacitor C has no voltage drop across it when the circuit is in the off state.  Once a control signal is applied, the capacitor acts as a short circuit causing high inrush current limited only by RI through the LED.  After capacitor C is charged, it acts as an open circuit; thus RI and RF determine the LED current.  Based on the previous example, the maximum value for RI+RF=714W

For example to speed up the turn on time, we can increase the IF current from 5mA to 20mA.  The VF value at 20mA and 85oC from Figure 3 is 1.11V

Figure 1: PhotoMOS fast switching circuit

Thus, a standard resistor value of 150W should be selected for RI.  Now the value of RF can be determined as follow:

This yields a standard resistor of 560W.

Assuming same criteria as before, 5% tolerance and a temperature coefficient of 250ppm per oC, RF of 560W can no longer guarantee safe operation over the entire temperature range.

Ensuring Safe Operation

This value is higher than RFmax.  Therefore, RF must be reduced to the next lower standard value of 470W to insure safe operation over the entire temperature range.  The next step is to determine capacitor C value.  The time constant of an RC circuit is the amount of time it takes to charge the capacitor to a certain level.  After one time constant the capacitor will be charged to 63% of the applied voltage.  The following assumption can be made to calculate capacitor C value: time constant t = RI x C shall equal twice the maximum turn on time t =2 x Ton and the maximum Ton is 2ms

Thus a standard value C = 22mF should be used in this circuit to insure a maximum turn on time of less than 2ms.

If you have any questions on how to optizimize turn-on time of a PhotoMOS, please use the Comments section.

January 16, 2012 / Tom Monczka

CES 2012

More than 140,000 attendees were at the 4 day show covering 1.8 million plus square feet of space with over 3,100 exhibitors. Stakes are high with projections estimating $200 billion of CE gear will be sold in the U.S. during 2012, an increase of 3.7 percent over 2011. Celebrities at this year’s show included Tom Hanks, Justin Timberlake, Ryan Seacrest, Will Smith, LL Cool J and Kelly Clarkson.

Panasonic

A wall of 3D TVs dominated the Panasonic booth with stadium style seating for viewers to fully experience the latest 3D technology. Highlights from Panasonic’s booth space include: electric car technology and charging system, advanced Li-ion batteries, solar car, smart energy gateway for energy management and a live social network broadcast.

Taylor Outlines Panasonic’s Near Future (interview with CES Daily)

Joe Taylor, Chairman/CEO of Panasonic Corp. of North America, outlined the company’s strategy to expand beyond A/V business in the near future. Panasonic North America is expected to post a profit by the end of the fiscal year on March 31. CE sales are lower with higher sales on B-to-B segment (globally consumer sales are 50 percent of revenue). Short term focus in the next two to three years will be on the B-to-B side. Initial investments in cloud-based initiatives include healthcare to allow doctors and hospitals to interact with consumers at home. A reduction of smaller plasma sizes and increase in larger plasma and expansion in LCD are planned. Ninety percent of the lineup will feature 3D and 94 percent will include smart TVs.

Intel Ultrabook

Ultrabook laptops using Intel technology are under 5 pounds, less than 1” thick, take 7 seconds from sleep mode to up and sell for under $1000. Promotional campaign for the product includes an interactive display using Panasonic’s D-IMager 3D image sensor. Gesture control enabled by the D-IMager enables the user to virtually explore Ultrabook features using a menu driven system in an intuitive manner. Also on display was an augmented reality interface deployed in Lego stores using Intel technology.

Omek Interactive Software

Omek is a middleware partner for the Panasonic D-IMager and showcased 2 interactive software experiences: Intel Ultrabook and 3D car explorer. Intel’s Ultrabook software is based on Omek’s development platform and includes a menu driven system to explore the laptop’s features. 3D car explorer enables the user to virtually kick the tires on a car and start the engine, turn on the radio, and view the engine bay. Gesture enabled technology allows navigating the interface in an intuitive manner and is completely natural even for first time users. All 3 versions of the D-IMager were on display: EKL3104 (standard), EKL3105 (high accuracy) and EKL3106 (high ambient brightness).

Verizon 4G Kiosk

“Retail in the cloud” is a concept Verizon developed from commercially available components. POS system is designed for retail locations where the user initiates by tapping a smart card to load stored data from the cloud. For a clothing retailer the user can have an avatar stored under the account. High speed LTE (4G) allows others (say store assistance or a friend) to join by video, view the clothes and comment from a remote location. Going wireless simplifies the installation and allows the kiosk to easily be moved to another location if traffic is low in that spot. This is a perfect fit (pun intended) for 3D image sensors employing full body tracking and gesture control. Sensor enabled kiosks are expected in the near future and will allow a virtual dressing room experience.

Mercedes Dynamic and Intuitive Control Experience

This technology won’t be in production soon but is an indicator of the direction vehicle manufacturers are going. An autonomously controlled car frees up the driver to interact with the environment by way of a windshield projected display and gesture control. One possibility – traveling through a neighborhood where your friend sends you a message to meet at a local bar. Display will show an incoming message and proximity of the location on a translucent overlay for a section of the windshield. Using gesture control the driver can identify the location on a map and initiate a response (“10 minutes away – see you there”) using a voice recognition program to translate into text. System is designed to differentiate driver from passenger and there are endless options for the interface. A myriad of safety issues need to be resolved for this to make it into production and could take 5-10 years before aspects of this concept appear in vehicles.

Audi Heads Up Display

Audi showcased a heads up display concept using 2 time-of-flight sensors for gesture recognition. Displays are split into driver, passenger and center location on the windshield. One example is to project GPS turn signal information on the driver’s side view while the passenger can select a multimedia experience. Driver and passenger are not able to see the other’s view, most importantly protecting the driver from distraction. All controls are initiated using gesture control and production is to be determined.

Ford EVOS Cloud Vehicle and Focus EV

Ford displayed the EVOS concept car embodying the company’s new design direction and showcasing technology as a cloud connected vehicle. Enhancing driver health is also a goal using a heart rate monitor connected to the cloud that monitors the physical state of the driver and adjusts the driving experience accordingly. Focus EV was shown and incorporates a clever illuminated ring around the swiveling panel covering the charging socket. Charging status and battery level are shown in increments as the ring illuminates full circle. A Level 2 charger made by Leviton intended for the Focus EV was on display with an expected cost of $1500 including home installation at Best Buy.

HzO WaterBlock Technology

Revolutionizes the concept of guarding electronic devices from water using proprietary nanotechnology that blocks out moisture without interrupting electronics. Protects from splashes, humidity, spills and even immersion on a molecular scale. A chemical vapor deposition blankets vital electronic circuitry with a nano-thin film. As a result highly effective water-repelling properties can be applied to plastic, metal and ceramic. The finish is transparent and doesn’t change the look and feel of the device. Intended for use at the production level and compatible with any electronic device. HzO’s display included smart phones that underwent the process and submerged in a tank (and functioning underwater). This can be applied to any object – paper sheet or tissue for example – and shows no signs of moisture after removal from water submersion.

Duracell Powermat Inductive Charging

Inductive iPhone charging is debuting in the 2013 Chevy Volt. Inductive technology enables charging your phone by placing on a compartment in the center console. A receiver case snaps onto the back of the iPhone and enables wireless charging on any Powermat surface. Inductive charging is considered safe and the charging surface is indistinguishable from the plastic console. The charging area will have a cover similar to the center armrest console opening up to a storage bin. Possibility to expand into other vehicles in the GM lineup by 2015. Duracell will develop wireless charging stations for a variety of environments, including sports arenas. Jay-Z was recently signed on as the spokesperson and will become an investment partner in the company.

  


January 10, 2012 / Aiman Kiwan pewa

Circuit Design Criteria for PhotoMOS Solid State Relays

In an earlier blog post (here) , we described the principle of operation of a PhotoMOS solid state relay. Now we’ll look at some considerations when designing the circuit around the PhotoMOS.

Choosing An Input Resistor:

The most basic method to drive a PhotoMOS relay is to apply a switchable voltage directly to the input pin of the PhotoMOS through a resistor to limit the current through the LED (Figure 1). It is very critical to choose the correct RF value to insure that the LED turn on to full intensity, but will not be overdriven by the input voltage.   The Rvalue can be calculated using the following formula:

Figure 1: PhotoMOS relay basic input circuit

Temperature must be taken in consideration when designing any electronic component.  Since the LED operating current increases as the temperature rises, we must use the typical IF value (typical recommended value is 5mA) at the maximum operating temperature of 85oC to insure safe operation.   The LED forward voltage (VF) depends on the forward current (IF) and the temperature.

Figure 2: LED forward voltage vs. ambient temperature

Let’s for example calculate the RF value for AQV210 PhotoMOS.  Figure 2 shows the LED forward voltage vs. ambient temperature graph for the AQV210 PhotoMOS.  The LED forward voltage with IF of 5mA at 85oC is 1.03V. The maximum RF value can be calculated as follow:

Assuming a 5% tolerance and a temperature coefficient of 250ppm (Parts Per Million) per oC, the appropriate RF value will be the next lower value from the standard resistors: RF=680W. This will insure safe operation over the entire temperature range.  If the supply voltage (Vcc) contains a ripple, the lowest possible Vcc value should be used for the calculations.

Figure 3: PhotoMOS relay transistor input circuit

Although power consumption and drive current for PhotoMOS relays are significantly lower than electromechanical relays, some logic circuits can not drive the PhotoMOS directly and require some additional components.  Using a transistor as a control mechanism to switch an external power supply is one method that is typically used by circuit designers.  Figure 3 shows the PhotoMOS input circuit with external power supply controlled by a transistor.  In this scenario the transistor is controlled by the output of the logic circuit.  When the transistor is turned on, it will create a path to ground for the power supply Vcc thus turning on the LED.  When calculating the RF in this circuit, we must account for the voltage (Von, typically 0.4 to 0.7V) drop between the collector and the emitter of the transistor.  Using the same example of the AQV210 PhotoMOS, RF can be calculated as follow:

Assuming a 5% tolerance and a temperature coefficient of 250ppm per oC, RF of 680W can no longer guarantee safe operation over the entire temperature range.  In this case it is recommended to use the next lower standard resistor to insure that RF is lower than the maximum allowed value of 714W: RF=560W.

In the next PhotoMOS post, we’ll discuss how to optimize the switching time .

January 5, 2012 / Kasey Mirecki

PID – Tuning A Control Loop

Tuning a control loop – PID – is the adjustment of its control parameters (gain/proportional band, integral gain/reset, derivative gain/rate) to the optimum values for the desired control response. Stability (bounded oscillation) is a basic requirement, but beyond that, different systems have different behavior, different applications have different requirements, and requirements may conflict with one another.

PID tuning is a difficult problem, even though there are only three parameters and in principle is simple to describe, because it must satisfy complex criteria within the limitations of PID control. There are accordingly various methods for loop tuning, and more sophisticated techniques are the subject of patents; this section describes some traditional manual method for loop tuning.

Designing and tuning a PID controller appears to be conceptually intuitive, but can be hard in practice, if multiple (and often conflicting) objectives such as short transient and high stability are to be achieved. Usually, initial parameters need to be adjusted repeatedly while PID is running until the closed-loop system performs or compromises as desired.

Some processes have a degree of non-linearity and so parameters that work well at full-load conditions don’t work when the process is starting up from no-load; this can be corrected by gain scheduling (using different parameters in different operating regions). PID controllers often provide acceptable control using default tunings (or auto-tuning), but performance can generally be improved by careful tuning, and performance may be unacceptable with poor tuning.

Manual Tuning
If the system must remain online, first set Ti and Td values to zero*. Increase the Kp until the output of the loop oscillates, then the Kp should be set to approximately half of that value for a “quarter amplitude decay” type response. Then increase Ti until any offset is corrected in sufficient time for the process. However, too much Ti will cause instability. Finally, increase Td, if required, until the loop is acceptably quick to reach its reference after a load disturbance. However, too much Td will cause excessive response and overshoot. A fast PID loop tuning usually overshoots slightly to reach the setpoint more quickly; however, some systems cannot accept overshoot, in which case an over-damped closed-loop system is required, which will require a Kp setting significantly less than half that of the Kp setting causing oscillation.

Effects of increasing a parameter independently

Parameter

Rise time

Overshoot

Settling time

Steady-state error

Stability

Kp

Decrease

Increase

Small change

Decrease

Degrade

Ti

Decrease

Increase

Increase

Decrease significantly

Degrade

Td

Minor decrease

Minor decrease

Minor decrease

No effect in theory

Improve if Td small

* Use minimum value possible in case PID Functions (F355 & F356) doesn’t allows you to use zero as a valid number. (PLC can error out in case zero is not allowed but is being used in the logic and PID is triggered)