Jul 23, 2013

QTC Moves to the Screen

posted by Bryon Moyer

Not long ago we looked at Peratech’s QTC technology. You might remember it as a functional ink that’s highly sensitive to pressure. Our focus at the time was how the technology works; designs seemed to be in process at that point.

Shortly after, they announced a touch screen solution. Because of the ink’s sensitivity, they can actually put the touch sensor behind the screen, reducing the cost of the screen itself and getting the electronics out of the way on the edges. They can also make the screens arbitrarily large. But more importantly, the touch layer is no longer in the light path, meaning that it doesn’t absorb any light, meaning that power can be reduced for the same effective light output.

They recommend it in particular for e-paper and OLED screens, although it will work with anything except LCD (which doesn’t like to be pressed). You need to deflect by about a micron for it to register, but it can also measure the amount of deflection, meaning you get a pressure/z-axis component as well as the usual x and y components of the press.

You can find out more in their release.

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Jul 22, 2013

Antenna Tuning Without MEMS

posted by Bryon Moyer

Quite some time ago, we reported on WiSpry, a MEMS company that was using its technology to switch capacitors so that the antenna tuning can be optimized and changed in real time as conditions and needs change.

Much more recently, a new solution was announced based on collaboration between Taoglas, who makes antenna assemblies, and Peregrine, who produces an array of digitally-switchable capacitors (amongst other things). They’ve combined the two into a module that can fit into phones and other devices like automobile telematics and patient monitoring devices that have to be small and yet communicate afar. You might think this sounds just like what WiSpry is doing, but, while they’re attacking the same basic problem, their solutions are very different.

Peregrine’s capacitors aren’t actuated by MEMS elements; they’re switched electronically using Peregrine’s UltraCMOS process, which relies on silicon-on-sapphire technology to provide good RF performance. So they’re purely electrical where WiSpry (and also Cavendish Kinetics) is electromechanical.

So which one is better? I asked what the benefit of the electrical version is, and I can oversimplify the answer as being, “We can actually produce ours reliably.” (They didn’t articulate that in a snarky fashion, to be clear… Yeah, I’m sexing it up to keep your attention…) Which suggests, of course, that MEMS makers can’t.

So I asked both WiSpry and Cavendish Kinetics about this; I can’t imagine either one of them saying, “Oh yeah, our production sucks!” even if it were true (and, for the record, I’m not saying it is). But it’s only right to let them respond, so I checked in. Cavendish Kinetics’ Marketing and Biz Dev EVP Larry Morrell said that they have real customer designs in the works, but that they haven’t reached production status yet.

But significantly, he said, “Based on our collective management experience (and the management team has done all this before), we are on a normal yield learning curve for a CMOS process.  So we are tracking to our plan and the yields are improving monthly.  Our current yield levels are well above minimum requirements to be able to predict fab output to support customers.” Carefully worded; it suggests to me that yields aren’t great today (a threshold of predicting output simply means stable, not high) – but if they can support customers without going out of business, that’s all that matters to customers. They expect production this year and capacity in the 10s of millions per month by the end of the year. [Update note: more clarification on Cavendish Kinetics yields can be found here.]

I did not receive a reply from WiSpry by “print” time.

You can find out more about the Peregrine/Taoglas offering in their release.

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Jul 18, 2013

A Reverse Proof Mass?

posted by Bryon Moyer

This continues both the theme of “stuff at Sensors Expo” and non-traditional approaches to common sensors. Only this time, it’s the most ubiquitous of motion sensors, the accelerometer.

Most accelerometers use some sort of “proof mass,” a piece of silicon or metal or quartz or… whatever. Inertia makes the proof mass “move” in the opposite direction of acceleration, and you can measure that apparent movement.

Memsic (whose mag sensor we just looked at), does something different. The fundamental principle of inertia is still the same, but the proof mass, well, isn’t a mass. If you’ve ever carried a helium balloon in your car, you’ve seen the effect. (I haven’t, or I haven’t been perspicacious enough to notice and remember, so I’m taking their word for it.) When you accelerate your car, you’d expect the balloon to move backwards, just like those toys and stray French fries and the dog do.

But it doesn’t. It moves forwards. Why? Because the gas is lighter than the surrounding air (even compressed in a balloon), and the heavier air moves back, displacing the balloon forwards.

Memsic exploits this same behavior by heating gas in a cavity. They use nitrogen, although that’s not really critical. The point is that, by heating the middle of the chamber, you get this “ball” of warmer gas (I keep wanting to call it a “bolus” but I’m not sure if that word would apply). This heated mass is less dense – and hence lighter – than the gas on either side of it. So when the unit accelerates, it moves not back, like a normal proof mass would do, but forward, in the direction of acceleration. It’s like the proof mass is all the non-heated gas.

By putting temperature sensors at either end of the chamber, you can detect the approach and retreat of the heated gas and use that to signal acceleration.

The benefits of this are that you don’t get any of the messiness of a normal proof mass. There are no issues of shock, vibration, resonance, or stiction. Its calibration is more stable and it has better bias stability. The main drawbacks are that it’s not particularly responsive, so you can’t do high-G shock detection. And, of course, you need power for the heater, although they say it’s not that much – you could still use this in a phone.

The primary apps they’ve seen so far are for electronic stability control in cars and high-end inclinometers.

You can find out more on their website.

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