Here are some basic "circuits" I used to function as switches for ac current controlled by the arduino. The arduino puts power to a transistor, which controls the relays. The resistors are used to drop the base voltage because the transistors need a good voltage differential between base and emitter to operate.
This is the project I did with Patricia and Stefanie for physcomp it is a TV that we rewired to listen to the amplitude of noise in a room. The above is a schematic of the final wiring we did for the TV. The basic interaction is triggered by the TV’s noise threshold being reached; it then turns the TV programming off and tells everyone to pay attention. We originally wanted to deal with the content of the program as well as the physical interaction that takes place when a TV is present, but due to time constraints we decided to emphasize the physical aspect. We were looking at what the mechanizes that defined the interaction of the user and the TV. We wanted to reveal the implicit nature that lies behind the TV medium and the forceful interaction that it demands when it is present in a room. This interaction often times takes over the language of everyday interpersonal relationships supplanting the everyday lexicon with one of its own choosing, making you speak “TV.” and hear in broadcasting. This can function because of the space that we relegate the TV to. It inherently has fewer barriers than talking to a person because it appears to be non-partial and objective. So at the very least the project is a bit funny because our TV becomes very partial in a very dumb way hopefully reminding you of what the object is and what its role can be. And at the most it will help to watch other TVs with the same skills you use when talking to a person.
click view image to see the circuit diagram.
This opamp seemed to work better than the lmn356 I got more gain and the output numbers didn’t fluctuate as much. The circuit is just two op amps in series the first cleans the ac voltage from the mic with a capacitor and then "rides" it on a 2.5 volt dc current so you get 0 as the base value and not a negative number. The second takes that signal and grounds the base voltage and then amplifies it so you get an output value of 0 to ~ 4v if you yell into the mic. The basics of an op amp is a comparator circuit, the circuit takes two positive voltages into an inverted and non-inverted input then compares them. If the non-inverted voltage is higher then it saturates to a positive voltage if the inverted is larger then it saturates negative or “low”. The key to the amplifier circuit is a feedback resistor (R2, R3) between the output of the circuit and the inverted input. This sends back a “dampening” voltage to the input not allowing it to fully saturate and controls the output voltage. This signal is ok but there are kits out there that give you a great range (the super snooper kit) and you don’t have to worry about trouble shooting them, but this opamp gives numbers that seem to be smoother than other op amp circuits so it worked well for the microcontroller application. to see the schematic click on view image.
this is the isd voicechip record/playback device we are using it's really easy to use and it is from carl's electronics. it has about 40 seconds of record time. if you want the schematic click on veiw image.
