Robotics Education & Competition Foundation
Inspiring students, one robot at a time.

Inside an audio signal generator


Entry ID #: 3204
Created: Mon, Jan 9, 2017 11:49 PM

Inside an audio signal generator: the inner beauty of an electronic device Team of Hangzhou Xuejun High School Robotics Lab Abstract As we all know, interesting gadgets always exist in a robotics lab. During a recent cleanup, we Accidentally found a device called audio signal generator (model SP121B). After a quick research, we found out that this device is owned by a retired teacher who is also an audio device enthusiast. It was used to generate audio signal,however, due to the lack of maintenance it could not be utilized any more. After getting consent from lab teacher, we tore it down to learn how it works.   Components Tearing the whole signal generator down, we found numerous components including micro controller (MCU), variable-frequency drive (VFD) driver, hex inverter, digital-to-analog converter (DAC), DDS waveform generator, analog multiplexer, comparator and lots of operational amplifier. We searched for information of all components we found by finding critical information on them, for example, part ID, which is used to identify component. We found that all multiplexer, comparator and some operational amplifier were Texas Instruments’ products. For more information about components we found, please see the table in the attached file.   Discoveries With existing information and the internal structure that we discovered, we assume once user sets target output frequency using specific button sequence, these button signals will be detected by VFD driver first. Then VFD driver will pass instructions to MCU. Since this controller is the “heart” of the whole device, it will set pixels’ status on the LCD display to present essential information to the user (for example, target frequency). Device microcontroller (MCU) is responsible for selecting the best signal generator to achieve the best performance at the target output frequency. When the user presses button to turn the device on, it will determine whether to use the DAC or DDS waveform generator. After generator selection, the microcontroller tells the multiplexer to switch the signal line according to user’s selection. Then, it sends signals to selected signal generator, which immediately starts generating the unamplified output signal. The signal will flow through the multiplexer, the Operational amplifiers and a transistor-based amplifying system.   Finally, the powerful output signal is ready to use. Meanwhile, the microcontroller generates some additional signals, which routes through the hex inverter or the Operational amplifier and finally goes into the TTL Output port or the Sync Output port.   For more information, please check the full diagram in the attached file.   Conclusion Our team solved lots of problems of taking pictures, finding chips’ function and composing this essay. All team members participated in this activity using our collaboration skills to get things done. That reminds me one proverb called “One finger could not lift a stone”. We found out that every chip on the logic board is essential – just like our team. We might now be able to feel the beauty outside, but after tearing it down and learning how it works, we discovered the ultimate inner beauty of an electronic device. And this integrated inner beauty exists everywhere in the world – and every engineer are working hard to achieve the future vision. This world is made up by everyone – so we need to get inspired by the motivation to achieve more. 


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