First Innovation in Robotic Sensors in 3 years!

Strange. This sounds like a more clunky version of the Motorala e-Field sensor.

-- D. Jay Newman

This looks to be a rip off of Motorola's E field sensor devices. Looks like someone violated someone's patents. Besides Motorola was giving them away free for a Circuit Cellar contest last year. I wonder if he used the Motorola chips in his system?

Did they licence Q-Prox?

This is an old, old idea. It was once called a "capacity operated relay". There are lots of variations on this theme, running touchscreens, touch lamps, elevator buttons, and related devices.

Now the next thing would be to build a time of flight/phased array version. Get real distance measurements. And, sure enough, somebody has done that.

>This looks to be a rip off of Motorola's E field sensor devices.

Friction Stir Welding! Now that is a really cool idea, thing, thought.

It's more than an idea/thought.

--kyler

The other chips that are discussed are not appropriate.

On the discussion group site:

Mr. Fritz writes about the Motorola chip, e.g. which I have copied below:

I first started this project using the MC33974 back in mid November. I overnighted the eval kit in from DigiKey thinking I would be all set...

Unfortunately, the MC33974 is very insensitive. It can detect a car seat (it's real use) but it cannot detect to the fine levels needed for robot work. With a 10 bit AtoD (it has analog output), the chip can go to 0.1pF if you are "really" lucky. Most of the details I stuck here:

Although neat for many uses, it was instantly obvious that the chip was not going to work for the range of 0.0001pF which such a system really needs. I gave the kit to a guy at the robot club for his object grabber where it might be more useful (I think I also have a bunch of bare chips in my junk box...). I then started looking into the theremin's circuits. There was a version-I which used all analog circuits that is still described at:

However, the new all digital version is vastly better and really made this whole system fly:

ThereminVision can detect capacitance levels about to 1/10000th what the Motorola chip can. The Motorola chip does have nine channels and can do shield referenced antennas which is cool, but the sensitivity is just not there.

The key difference is that the Motorola chip just sets up a 120kHz capacitance controlled oscillator and measures the frequency delta directly. A nice solid thing for critical car safety systems, but too insensitive in our case. However, ThereminVision "heterodynes" the oscillator signal with a reference signal just like the theremin instrument to run the sensitivity way up while still remaining stable. That is the key difference. This is all explained in the manual under "Theory of Operation" on page 5.

What is really sad is that apparently the Motorola chip was originally going to heterodyne the signal against a reference and be very sensitive just like the theremin. I might guess that the analog designers were just not able to get it going or the car application changed there plans with million piece sales prospects. ThereminVision could actually be adjusted to be just as insensitive as the MC33974 if anyone really wanted too. If they had just gone all digital and allowed for the full range of sensitivity adjustment, the Motorola chip might have been perfect for everyone!! But they didn't... Maybe someday they will... The Motorola package is also pretty messy for home soldering and such. They added a bunch of automotive things too like the incandescent dash board light driver circuits (it does have an error signal if it burns out :-p).

If I have not already told you far more than you wanted to know ;-)) Here are two posts that go over this too:

There has been a long running saga about this at:

All the relevant posts are "MC33947" or "ThereminVision" reports.

Cheers,

Terry

(via Bob Leonard)

Sorry, but I feel that the other chips discussed are higly appropriate.

This is a robotics newsgroup, and not an advertisment for the theremevision.

Also, the first posting stated that the theremevision was a "new" and "innovative" sensor. Indeed, the claim was that it was the "First Innovation in Robotic Sensors in 3 Years".

Frankly, this is what I was disputing. This is *not* an innovation. It is merely an improvement of an existing sensor technology.

-- D. Jay Newman

Agreed.

It's a nicely executed project, though.

Once you get past the awful web site design and find the manual

there's some good stuff in there.

John Nagle

D. Jay Newman wrote:

I think advertisements are welcomed if they are robot related. I just bought one of these kits for 50 bucks for my ER1 platform and will post the test results here.

The subject line may be a bit exaggerated but it did catch my attention. I don't think it's a big deal if the product is affordable and can improve our robots. We'll see.

DT

Yes, I can see that now. Unfortunately I didn't see that in my first look at the web site.

They look interesting, but I *really* hate two things about this site:

1. The blinking text! I hope there is a special place in hell for the programmer who inserted the "blick" tag into HTML.
2. Even worse, I couldn't find the price for the kits until I actually clicked the "buy" button. I then had to cancel the purchace as all I was looking for was the price. Plus it took several clicks to get to this place.

On the other hand, I will probably buy a kit next month or so.

-- D. Jay Newman

Agreed. My objection was not to the original posting being an advertisement, but to Bob's attempt to close discussion about the topic.

I'll probably purchace a kit next month. This month I already have enough budgeted under the topic "robotics".

-- D. Jay Newman

1.A close friend called the web site 'Visually Unappealing'. My own characterization is: Amateurish. And I wrote it. I'm obviously not a web designer. The web site was rushed. The Web design company told me, at he last minute, they were over-comitted. The site will get a facelift (hopefully sooner than later)

1. I'm sorry if it appeared I wanted to shut-down a discussion. That was not my intent. I wanted to point out that the kit designer did not like the chips being discussed and his reasons for rejecting those chips.

2. I could have made it more clear, I suppose, that if you had any questions for Mr. Fritz, he is monitoring the discussion group on Yahoo and I'm sure would respond to any Yahoo posts

Bob Leonard

Good luck responding to Yahoo posts. I quit trying to use that crappy, unreliable forum.

BRW

So, what was that innovation three years ago???

-----

Indeed. I hope someone with more information posts here where everyone can easily follow.

I'm thinking that these sensors *might* be useful for detecting obstacles around a wheelchair robot I'm trying to develop as a research project.

--kyler

I still follow a couple of groups which are only on Yahoo, but their licencing policies pretty much keep me from posting code there.

-- D. Jay Newman

Hmmm. I went to the website. Looked for about three and a half seconds, and didn't see how this is a "vision" system.... went back while writing this just to make sure, and took a longer look. Understand, I am not knocking it... looks like a useful proximity system. It just doesn't seem to be what I'd call "vision."

Am I correct in my understanding that the four antennas on the corners of the example 'bot are the sensors? And that the information they give can be interpreted to give a direction, from a reference point at the center of mass of the four antennas, to a nearby object? The website was kind of sketchy on the kind of data that the thing would collect...

Does it resolve distance too, or just direction?

The kit designer responded to you question on the discussion group:

His answer is below:

Hi,

I really did not think about the name very much. I wanted to certainly credit Leon Theremin. I quickly though of a few terms and just started using "ThereminVision". Then I made PC file directories called ThereminVision and started naming all the files with it. For better or worse, that is the name that stuck. If I had thought about it "too" long, it may have been named something like "Pentium", "palladium", or ".net" :0))) I guess I really like the name. The "theremin" right off tells a lot of people how it works and the "vision" thing sort of indicates it help a robot "see" what's going on out there. But it is certainly not like a TV camera or true image processing thing at all.

The four antennas are indeed proximity sensors. They detect capacitance change caused by an object near the antennas. If we take the case of just one antenna, there is no direction information since the object would "look" the same in any direction. With two antennas, we can tell if the object is closer to one more than the other or if the object is centered (near equal readings). We still really would not know where in the center it is (front, true center, behind), but rather that it is just equally distant to the two antennas. With three antennas, you can "triangulate" and pretty much determine the general direction. Four antennas fit most robots well so there ended up being four. The number of antennas "could be" more or less. Four just worked out well without adding complexity in our case.

For distance, we can just look at the one antenna case as an example. If we have a reading of say 1000, we don't really know if it is a full size car 10 feet away or a fly sitting on the antenna. Each could give the same reading. A tiny fly very very close, or a giant metal object far off. But we can guess about "what" we are looking for. Say it is a 10cm x 10cm sumo robot that we are really looking for. Since all little sumos will "look" very much the same. We could make a little table of readings vs. distance and it would be fairly close for all sumos.

I should point out that one may not really need to worry too much about distance. In my case, I just look for "anything" out there and attack it >:o)) In a Critter Crunch match, there is only one other thing out there, the opponent robot, so I go for it. One "could" make things very complex by reducing the readings to degrees, velocity, meters, Farads... but the number crunching gets to be hard for a little microcontroller. But if one wants to crunch the numbers, you could get a lot of info other than just which direction to attack.

Cheers,

Terry