DTMF project

Saeed

Hi all members ..

i'm a new member here and i need help in this project .. i couldn't understand it ..

thanks

Objectives:-

Get an introductory level of familiarity using CAD tools.
- Take a practical problem described verbally and convert it to a digital design problem
- demonstrate your ability to search for and understand the operation of the DTMF circuit. .

Problem Definition:

Search for the data sheet of a DTMF (Dual tone multiple frequency) IC. You can use the EE department store
or internet.
a. In your own words, describe the operation of DTMF. What are the inputs and outputs? Draw the
IC (Block diagram not the internal circuit) showing all inputs and outputs.
b. Assume that the output bits of the DTMF are ready and available for your digital circuit,
 Design a logic circuit that controls several home devices (at least four)
 Your design should be able to turn on and off any selected device without affecting
other devices. For example, turn on device A and keep other devices unchanged.
 Clearly describe the operation and your input/output assignments.
 Add security features like a password.
c. Test your design and show the result using the LogicWorks

Rules:

 You must work in groups of two.
 Each group must work independently.
 You must depend on yourself in this project.
 All information is available on the internet and in the EE department store.
Include a complete set of design notes, circuit printouts, and simulation results in your report. Your simulation results
should show that your circuit meets all of the project specifications. Indicate which simulator including the version
number that was used. The due date is Monday January 02, 2012. You should also hand-in your report and a
CD containing your CAD design/simulation and the doc version of your report.

Mike Green

We can't do your project for you. The project's Objectives and the Problem Definition spell things out pretty carefully. You have to demonstrate your ability to do research into how a DTMF circuit works. A good starting point is the Wikipedia. Start with their article on DTMF and follow any links they provide. The Problem Definition tells you where to start looking. Do what it says. Try searching Google for DTMF and see what you get. If you've done all that and you still don't understand, feel free to ask specific questions. We'll be happy to suggest other sources to look at. If you still can't understand the project, you'll have to have a talk with your instructor.

Saeed

thanks Mike !

i know how to do this project but i am just a little confused about (for example) how to add security features ?

another thing is that i have a lot of ICs that represent DTMF so should i choose one and work on it ?

thanks again

Mike Green

You can define what you mean by security features. For example, most telephone answering machines provide for a password that you enter when you're setting up the machine. If you're calling in from outside the home, you have to provide the password to be able to control the answering machine (like to get your messages). If you have an answering machine at home or a friend has one, borrow the manual and see how it works. You could duplicate that scheme or modify it for your own needs. You can also look on the internet for answering machines and download some representative manuals from the manufacturers' website to look at ... they're all on the internet these days. It's certainly possible to do this project without using a microcontroller, but it's a lot easier if you use one. Any Parallax Stamp could do it (along with a DTMF decoder). A Parallax Propeller could do the DTMF decoding as well, but it looks like you're expected to use a DTMF decoder IC.

There are not that many DTMF decoder ICs on the market these days because a lot of microcontrollers can do their own decoding (look up Goertzel algorithm in the Wikipedia). Pick one that's on the market and work on that. Major distributors like DigiKey and Mouser have on-line catalogs that you can search for DTMF decoders or encoders.

One of the Nuts and Volts Columns is about a DTMF decoder and a BS1 (here and here). For the other columns, use the Resources tab on the main Parallax webpage. There's other information you can download via the Downloads button on the main webpage.