Delay line

The delay line shall be simulating the 72bit accumulator.

• The velocity, v, of sound through air is 343m/s.
• If distance if 1m, total delay is 1/343 = 0.002915452s = 2.92ms.
• Delay per bit is 2.92*10^-3/72 = 0.000040492s = 40.5us = 24696 = 24.7kHz
• Frequency is 343/(1/72) = 343*72 = 24696 = 24.7kHz

Require a clock with this frequency, will use a NOR gate clock circuit (resister values to be found). If fast enough an Arduino can be used as a counter to 74bits (2bits in flip flops). The first part of the circuit is a band pass circuit, depends on microphone.

Plan

• Step 1: get clock working (DONE)
• Step 2: check Arduino can be used as counter (DONE)
• Step 3: discuss and research a revised design if not (NOT NEEDED)
• Step 4: build voltage tap (DONE)
• Step 5: set up microphone and speaker in a tube (3D print) (DONE)
• Step 5.5: Buy lm741s and voltage shifter (End of Thur 3rd Aug)
• Step 5.8: Write blog post about so far
• Step 6: make band pass filter (with inverter) -> requires amplified output of over 2v
• Step 7: build output amplifier
• Step 8: test all so far works
• Step 9: build detection circuit & link to Arduino
• Step 10: voltage shifter at input and output to FPGA
• Step 11: interface (don't know how, will start by looking at Hatim's code)

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There are some problems that will be faced:

• Arduino not working (use two decade counters? add more to circuit?)
• Reflections (leave tube open? experiment with the reflections)
• Interfacing (since doing once hardware done may get hardware wrong)
• Tube too slow (Only send 72-x bits into the tube and store x bits on the Arduino)
• Tube too fast (Arduino can have a buffer or can build a buffer circuit)
• Voltages (have not worked out specific values, my have too many drops and require multiple battery packs)

Arduino pins:

• pin0: RX
• pin1: TX
• pin2: Speaker
• pin3:
• pin4: Microphone
• pin5: Frequency test
• pin6:
• pin7:
• pin8: Reset
• pin9: CLK
• pin10: counter 10
• pin11: counter 2
• pin12:
• pin13: test LED