Breaking down the Capaforce: electronics for signal processing

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Today, Nicolas, COO, and Pauline, Electronic development engineer give insight on how simple electronics can be put to the service of state of the art, disruptive technology.

Nanomade is the creator of the capaforce sensing technology, combining both touch and force in one sensor. Their patented smart ink deposits nanoparticles on the Capaforce sensors. The space between nanoparticles varies when pressure is applied on the sensor, which can be measured and determine force level and touch motions with a precision of up to 15 times that of current market offer, all while Ignoring unwanted interactions

The sensor can measure the force applied on any type of material : paper, wooden table, glass by using the variation of the resistance. As the capaforce is extremely sensitive and has endless use cases, the aim is “to find the right electronics that can optimise the sensor’s performance. “ says Nicolas.

It boils down to this : when we apply force on the sensor, it will result in it’s deformation. This change in deformation is highlighted by the resistance’s variation, which will serve as a measurement of the said applied force.

Creating the Capaforce sensor : the alliance of force and capacitive

Upon deformation, the smart ink on our Capaforce sensors has its deposited nanoparticles to move away from or closer to each other. This causes an exponential change in electrical resistance, allowing us to precisely determine the amplitude of deformation with a gauge factor is fifteen times higher than average.

The sensor’s thickness is of the order of a hundred micrometers, costing up to 10 times less than piezoelectric sensors. Associated with standard capacitive sensor technology, we were able to overcome the minor variations in electrical resistance of our deformation-sensitive (force) sensors. As a result, our CapaForce (capacitive and force combined) sensors ignore the unwanted interactions

The Analogic Capaforce

Applying the same force on a table or a sheet of paper will clearly deform both surfaces very differently: the signal may either not be detected or saturate. To convert a continuous signal to discrete values, Nanomade engineers conceived the Analogic Capaforce.

The signal can be amplified between 1 to 16 times or reduced, by modifying the gain. In both cases, the noise, or irrelevant data, also needs to be filtered out.
The Analogic Capaforce It is composed of 4 elements to ensure a high treatment speed of 50Hz.

  • The Capacitive Driver : harvest all the “touch value” on the surface (touch interaction like motions or level of force applied)every 10 millisecond
  • Numerical potentiometer : The potentiometer calibrates the sensors to stabilize the signal.
  • Multiplexer : Used to select the best signal to treat
  • Amplifier : Treat the signal by amplifying it (or not) relative to the at rest reference.

Depending on the use case, Nanomade engineers can optimize the analogic Capaforce to better translate the analog signal. They will focus on electronic efficiency, simplifying the tech for a significantly lower cost. If a project is about smart wooden tables, the sensors will never be used on any other surface, which means the amplification and calibration will not vary as much.

However, this practice raises two problems

Optimizing the electronics for all use cases at once

The first issue arises when companies do not have clear ideas or projects: how can Nanomade then demonstrate their Capaforce Technology to their potential clients ?

That is when the Dev kit comes into play. It is a plug and play overview of the Capaforce technology that could demonstrate the behavior of sensors on any type of shape and material. It is designed so engineers from different backgrounds or electronics lovers can quickly take in hand the sensor to test and visualize it’s behavior, and build a quick prototype.

 
 
 
 
 

Optimizing the electronics for extreme usage of the sensors

The second issue is how do Nanomade manage their technology for more advanced, extreme usage of the sensors ?

To answer this, we will take the example of the Pulse. The Pulse, is a non-intrusive, transparent wellness monitoring system, adaptable to any material and shapes. It is designed to improve your consumer experience needs by bringing Wellness Monitoring everywhere
The electronic of the Pulse is a first layer of signal processing, converting Analog to digital signal. The integration of the sensor is different, and with a very specific electronic conditioning to, from the moment the signal is perceived, draws out and interprets it.

To be able to interpret a signal, the main parameter is “the gain”: the signal has to be amplified a 1000 times, filtered out from the noise (the more a signal is amplified, the more saturation and noise appears) to optimally recover the BCG ( the ballistic forces of the heart valves).

    To filter the noise, the techniques used are :

  • assive components: resistance, capacitor…active: integrated circuits to make calculations, acquisition chain similar to that of the CapaForce with a processing speed of 250 Hz.
  • Capacitor and resistances to filter and amplify the signal. first order analog filter to remove unnecessary elements from the signal
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    To enquire about our sensors or request further information, contact us as [email protected]

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