IR Harp


Posted on Feb 6, 2014

A harp without strings i. e. IR sensor-receiver pairs function as strings in our device. The device senses when a string is being plucked (causes blockage of IR). Correspondingly, the particular sound is produced by Direct Digital Synthesis. We used 6 TSOP sensors to identify the blockage of infrared led`s. They then give digital output to microcontroller which


IR Harp
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processes data and gives 6-bit digital output to Digital to Analog converter(r-2r ladder). DAC converts the digital input to analog data which is then filtered and amplified to drive the speakers. The microcontroller is used to interpret the sensor data and output the stored waveforms at the frequency assigned to the plucked strings using an interrupt. Since we were somewhat familiar of sensors because of line follower competition, we knew that working with the photodiode sensors would be difficult as their alignment and low sensitivity were some of the major problems. So we found out TSOP sensors which gave excellent variation from 0. 0 to 4. 81 V. Then we worked with two sensors kept at a distance of 5 cm to test that one led is not interfering with another sensor. We used pipes to remove this problem. TSOP sensors require the IR LED to operate on a square wave of a particular frequency, which in this case was ~38kHz. We provided the required square wave form by a circuit using the 555 timer. We then used DAC0808 to convert the digital output of TSOP sensors into analog signal but it was not working as per our expectations so we designed our own DAC chip using r-2r ladder. We were then getting range from 0 to 4. 5 V. Now we wanted to amplify this signal without affecting previous circuit. For this purpose we used a buffer and an amplifier which then gave range between 0 to 8. 6 V. We then gave this output to speaker...




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