Members: Lara Dolecek and Daniel Yen
The purpose of our project is to built a speaking device that would enable a person with speaking difficulties to communicate better. We are now trying to implement a 2-button device, based on which we will model a more complex one.
This semester we had the opportunity to participate in both technical and service projects. One of the technical projects is to design a speaking device. This problem was first encountered in the Fall semester 1997, when the current members of the "Technology for Living" visited Center For Advanced Technologies. The original motivation was to build a recording device that would facilitate the communication of the handicapped community (especially people with underdeveloped motor skills), and be financially affordable. The then-current group started working on the implementation of this device. This project has been continued this semester.
In addition, "Technology for Living" has made valuable contacts with the Regional Center of the East Bay (RCEB). These new contacts are significant, because they provide our group with an opportunity to solve real-life problems that members of the physically challenged community could benefit from.
In order to accomplish our goal of creating a device that would record one long playable message, it was decided that a good starting point would be to use the ISD 1400 chip. ISD chips already have non-volatile analog memory within them, and each chip is capable of performing the functions needed, namely particular addressing, play and record ability, inputs for microphones, and an output to speakers. This was the same chip that was used in the spring of 1998 in order to design a device that would play 4 messages, each approximately 4 seconds each in length. The difference now is that our design is only going to store one message that can be up to 16 seconds in length.
In order to construct this speaking device, we chose to follow an example circuit model that was provided by ISD. The circuit diagram gives a general indication of where things are located on the chip. The notables are pins 16 and 17 which connect to the speaker, number 17 and 18 go to the microphone. Pins 23 through 27 take care of the play and record functions. The design essentially results in a three-switch device. One switch controls the power, one the record mode, and the other the play mode. The next page has the actual circuit diagram that we worked from, as well a more technical explanation of the circuit, which was provided by ISD. In it they discuss how the transistor comes into play, and how it is responsible for the storing and recording of information. They also provide reasons for why certain circuit elements were added. Overall, it provides a general overview of how the chip acts digitally, and with analog.
The circuit has been constructed on a larger breadboard, but the goal is to eventually reduce it so that it can fit into a more convenient packaging. Currently we are still in the debugging process. The several tests that we have performed on the circuit have failed. We are systematically checking the circuit in small sections. We should probably look into obtaining 47k resistors instead of putting two 100k resistors in parallel. If things look bleak, we may even consider rebuilding the circuit, but for now we will continue with the debugging process.
In the meantime, the group learned about the other product that ISD now has. ISD has recently started making new chips, known as 1606 family. The advantage of this chip is that it provides a single or a double recording in the duration of 4.8 to 9.6 seconds, and it also has a tone generator. In addition the actual circuit is much simpler than the one for the ISD1416 (the schematic of which is shown in the attachment). We have requested additional information about the chip. This information will be very useful when we receive the actual chip, which will be as soon as it becomes available on the market.
We are currently testing the circuit, and trying to fix the glitches. We are making some changes to this circuit, as we are trying to have the working version. Since the group has not yet completed the project successfully, the project will be carried into the next semester. We hope that it will be finished within the first couple of weeks of the upcoming semester.
Once the electronic works properly, the second part of the project will be to package the actual device. This is equally important aspect of our project because we need to fully satisfy our clients’ needs. One solution is to make a device with buttons large enough so that a person with reduced motor skills could use this device. Another is to make a smaller device, which should contain messages that are not often updated (like the example given above).
Note: Schematics and description of the ISD chips can be found at http://www.isd.com/products/.
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