Pressure Sensor Variation Brain-Storming

One of the challenges in an open-source project compared with a commercial approach, is that you don't have budget for lawyers to defend against (often frivolous) patent claims.  However, this can be more than offset by using a basic knowledge of patent law. Specifically, if you talk publically about something, no one can go and patent that, or anything that can be obviously inferred from that in any jursidiction thereafter. This is because the public discussion forms part of the "prior art" once it is made public, e.g., by being described in this blog post.  Unlike when you want to file a patent, this disclosure doesn't even need to be "reduced to practice".  There are a lot of names for this approach, but let's just call it Patent Spoiling. The idea is to make sure that you have plenty of freedom of movement in innovation, rather than have someone come and patent all the way around you, so that you can't change or improve anything.

So the purpose of this blog post is to brainstorm as many ideas as possible about the pressure sensors I have been designing, and related aspects of the system, so that we have that "vacant land" around us, that no one can build patents on to impede ongoing improvement of the pressure sensors and the riding simulators we want to build that incorporate them.

I like numbered items, so I will number these as I go along, starting with aspects of the current design. This also makes it much easier to slap any frivolous lawsuit down, by being able to refer to the ideas by their number.

1. A pressure sensor that uses a sandwich of electric fence tape between two pieces of conductive foam.

That's a very specific description. It doesn't protect us much, so let's broaden that out as much as we can:

2. A sensor that uses a two or more conductive elements which are connected by a medium whose resistance or some other measurable property varies when subjected to pressure, or via some indirect process that causes pressure exerted somewhere to result in a measurable difference in the measure property.

That's pretty broad now. In fact, if you were trying to write a patent, that "claim" would almost certainly be thrown out, because it is way too broad, and almost certainly overlaps with existing prior art. That's bad if you are trying to write a patent, as those overlaps will be removed from your claim (possibly invalidating it completely). But when trying to expand the prior art to prevent the prosecution of patents, it's a good thing, because your broad claim adds to the area covered by the prior art.

3. Conductive foam can be used on only one side, rather than both.

4. If the electric fence tape or other conductive element is stainless steel, or some other material that is annoying to connect to the rest of the system, then an interface can be used, e.g., copper tabs crimped or otherwise connected to the annoying material.

5. To improve the connection between the annoying material and the rest of the system, an intermediate material can be used, e.g., steel-wool, to ensure adequate mechanical connection.

6. Stainless-steel wool or another specialised intermediate material can be used to improve the properties of the system, e.g., to reduce galvanic or other corrosion effects.

7. The intermediate material can be sourced from existing products, such as pot scrubbing pads.  

8. In some cases, that existing product may require treatment, e.g., removing soap or other impurities from it, before it is useful.  

9. It's also likely that it will require mechanical treatment, e.g., cutting up into suitable size pieces and/or otherwise rearranging it.

10. You could use flexible PCB as the conductive elements.

11. You could use conductive pen to draw conductive elements on some other material.

12. You could add or replace a conductive element to the electric fence tape, e.g., by weaving a copper wire through, to avoid some or all of the problems of bonding an annoying material like stainless-steel to other components of the system.

13. You could use something other than electric fence tape as a medium into which conductive elements could be woven into or otherwise incorporated.

14. As an example, you could use shade-cloth material, and weave wires or other conductive elements in.

15. As another example, you could use a piece of plastic, wood, rubber, car tyres, carpet or other flooring materials, silicone or some other material, into or onto which conductive elements are incorporated, woven, drawn, painted or otherwise applied.

16. Similarly, the conductive foam could be replaced by another material that has appropriate properties.  For example, car tyres that have enough conductivity.

17. The conductive foam could also be replaced by another material that has been modified or enhanced in some way to provide the necessary properties. For example, by applying or otherwise causing or allowing a partially conductive coating to exist on something that is normally an insulator, e.g., by spraying a light coat of a conductive paint onto a piece of plastic.

18. In the opposite direction, you could cause or allow a resistive or insulative coating to exist on a normally conductive material. This could be as simple as allowing an oxide layer to form on a piece of metal.  All that matters is that you have some means of converting a pressure to a measurable reading.

19. In another approach, you could use changes in measurable properties that result from deformation, e.g., forming something like a strain gauge.  For example, carbonised rubber might have different resistance based on how stretched or compressed it is.

20. In some cases, you might need to use an operational amplifier or other circuit to make the measurement readable or usefully readable, whatever the arrangement and composition of the sensor system.

21. In some cases, you might need to use hardware, software, mechanical or some combination of these and/or other filtering elements and/or techniques to obtain a useful reading. For example, in my design, I use some simple software to filter out the mains power signal that is picked up by the leads of the sensor and/or by the sensor itself and/or by other connected components such as the power supply, so that a useful signal can be read out.  This might mean that you have to use and/or combine multiple readings of a sensor, e.g., averaging over a period of time, and/or identifying good times or time periods to perform one or more measurements, e.g., to identify the actual or approximate time of each mains power cycle, so that the averaging of the signal can be done more consistently.

22. In some cases, you might use differential techniques to subtract out some or all of the noise.  For example, you could subtract or otherwise combine the readings of multiple sensors (including dummy sensor circuits or parts thereof). For example, this might be able to substantially subtract out the mains power signal from the sensor readings.

23. Any or all of these or other techniques might also be used to remove other forms of noise from the system. This includes, without limitation, noise caused by (or even just modulated or otherwise influenced by) other parts of the simulator, such as motors (electronic, hydraulic or otherwise), hydraulics, sensors, moving parts and/or their associated electronics.

24. Multiple sensors could be constructed that share one or more of the elements of other sensor(s) or other components of the system. For example, vertical and horizontally oriented sensors of the conductive foam and electric fence tape type might be constructed using a single layer of conductive foam between the horizontal and vertically oriented elements.

25. The copper tabs used in the current design could be placed anywhere in connection with the electric fence tape or substitute, provided that they are not in direct electrical connection.  For example, they could both be placed at one end or on one edge, to allow sensitivity closer to, or entirely reaching, the opposite end or edge of the sensor. This might be useful, for example, for sensors in the mouth, where we don't want dead or reduced sensitivity at the junction of the rear wall and floor of the approximation of the mouth.

26. The amount of dead zone and/or reduced sensitivity of the sensor might be reduced by reducing or eliminating the area(s) of insulation required to keep the copper tabs or substitutes from forming an electrical connection that would otherwise spoil the sensor.  

27. The insulation or other means required to prevent a spoiling of the sensor could be bonded to or form part of the copper tabs or substitutes, or to some other element of the sensor and associated system.  This could take many forms, e.g., an insulating paint coat on one or more surfaces of the copper tabs or substitute, or something like using needle and thread to create stitching that prevents the tabs or substitutes from coming into spoiling contact with one another.

Woah, that's a lot of things already. I am sure I will think of more over the coming days, but let's just push this out already, so that we protect against patenting of any of that. That's another great thing about trying to spoil patenting an area, rather than trying to patent it: We don't have to cover all the area in one go at one point in time.