Class 6

Stable voltage is important!
We have big two goals. Talking about the readings, two technical material is not that technical. Nothing to demo. Identification versus location.
How php connects to sockets? Basically what you do, you set your arduino up sitting there waiting for connection, write a php script that conencts to that address, john schimmel did something similar. Turning LED on/off with php? You cannot do the way I describe, what to give the model: Web page is php it calls the server ask for information, server connects to xport and delivers the message.
Another model is far more difficult. Put webpages directly on the xport. IT becomes webserver in itself. Setup menu is oone webpage of xport. Another way you can do it, there is an online tutorial. tutorial about this at tom’s site.
You can even put java applets there, java applet sits on the xport it gets loaded on to your browser and browser makes a socket connection to xport to change it. He doesn’t advice doing it. You don’t full access to php over xport. In general the model to keep in mind in most of your project is central server to central xpository.
For your final you can do anything you want. What I wanna is, tangible networked interface of some sort. Simple as pong, or complex as sensing ambient conditions of your house etc. Datalogging project. Any applicationary is fair, good clear networking system. Any technology is fair game too. Next week we are going to start talking about ideas on that.

Identification versus Location

Walmart RFID tags. They were going to put tags on every product. RFID works like this: Few identification systems. barcode, light dark pattern. RFID is that you got radio tag on the product. RAdio is nothing more adjusments. Changing electrical signals adn vibrating. using a cap chargin the cap discharging it. Couple of things about that, where does the signal goes, how can we read that? A reader, if tag has no power source in itself how far do we need to read? A pretty close,. MAke the reader more powerful to extend the range. Danger, taking a powerful radio and stick it next to you, we are starting to radiate you. Frequency effects you. Penetration for your body. RFID readers is the simple form read only meter or less.

If I want to basically need to setup to know everything about chris based on his purchase. RFID, database. Walmart you get from the database. When you buy an rfid tag and reader you get a bunch of numbers. It is your responsibility to assign a number to it. It is not like, I can only use tag number between this and this. not yet. Access to the database that he is purchasing. The problem becomes complex. One of the big points about identification. Privacy violation. The more complex system the less chance it is going to become big problem. More aggreate the system the less the data becomes important. Separate the information. How do we arrange convenient data trace when keeping it still safe. Encapsulation helps the problem.
How do we rescue him in the physical level? Fry the tag. Blowing fuse on the tags, remove the tag from the company database.
Location, have an RFID tag, we wanna know where it is. WE need a lot of readers to locate it. If you got a very small place and sense that place you can sense it pretty easily. Sensing big place is harder you don’t have the resolution. one bit or 8 bits. Point is you need resolution to location. RFID is kind of sucks in this terms.
triangulation: trialateraing?I got two things that send signal back. Reader number one and reader number two. and we are somewhere between one and two, so in order to locate the object we can get readings from those reders and triangulate the object. IF we throw the third reader it gets better, ideally 3 should gives the position.
When we go more than two dimensions it gets complicated.
How can we go tracking items in other ways. We set a zero point, dead reckoning, it doesn’t know the location to any reference. SEtting initial location problems. Using acceleration as a tracking system. The problem it doesn’t get any data if you are on the constant speed. WE don’t have a constant fixed location.
Cell phones, 911. Your cellphone is putting out a signal that you can use. You are covered at least with three antenna and according to signal you can assume your location. IF you make a 911 call with your cell phone in 1000 feet your number will be forwarded to 911 by your carrier.
Walking along the broadway. multipass problem, because buildings are big we don’t get straight lines from the cell towers. It is hard to tell the location accuretly. same thing applies to GPS.

We wanna track people on each floor, why we are tracking people on each floor. TEchnological standpoint than a real application solution. How are we going to identify those people. WE don’t necessarily care where in the room, we care more if you are in the room or not. Point is not to track you 100%. How can we get the minimum amount of information but still get it.

Intentionally is biggest challenge we face. When iti is appropriate that we take advantage of this or not. Rob tried to do with zigbee and had some problems. We have some problems with the location as well. It is not only signals but also we need to identify those signals.
RF Radios basically can they broadcast and listen to anything on that channel, you can use make a mash up networks. Bluetooth is a system where you have to pair with each other. Much like a socket connection. There are some systems like zigbee ldon’t use pairing. Zigbee works similarly to UDP. They both share a broadcast address as well. Bluetooth relies two devices to pair each other. If you want to use zigbee for acknowledgment what would you do? WE need feedback from it. You would choose your protocol systems based on nature of intention. We have a couple of situations come up.

How much do I need to know, how little I need to know? It is important to make users feel secure.

Greenfield. People want to know what is happening, seaminglessness action. You want it to know and you want it to know in the moment. Mental model of how it works, all we have to do is want him to tell him. One particular thing: Thesis 48. When you make the system connectable people are start to connect everytime. Downfalls: First internet worm was not a virus, he sent a message to every server and got feedback. It became a worm. How would you avoid that problem. The problem with systems that are getting bigger, they can be hacked. Identify yourself to the system. When systems are open to all users this can create problems. Cash is different, it is such an agreement, noone has come up with something alternative to cash in the electronic sense. How do you know what you got is trustable? How far do we know it is real heart beat, how far do we care? New systems are emerging beside technologies that are put, regulated for us. Challenge before us is to make systems that people would trust, how do you get people trust what you are doing.