First attempts to get a distance, failed

The current setup, the breadboards with microphone and the robot with speaker

Last night I did a first attempt to measure the distance between the robot-Arduino and the other Arduino board.

Method

The robot first sends a synchronization through a wire (fatal mistake) and after a specific time interval the robot outputs a sound signal through its speaker. 

On the receiving Arduino I wait for the signal  through the wire and starts a timer when it is received and when the microphone picks up a sound the timer is stopped.

The time difference is multiplied with the speed of sound 340 m/s to get a distance reading.

Results

The issue was that the speaker produces A LOT of disturbance that passes directly through the wire. This is picked up by the sensitive microphone amplifier unit and since it contains the correct frequency it is identified as the right signal. 

Conclusion

Do not connect sensitive amplifying circuits to speakers (or motors).

I could have guess this would happen and kind of expected it, so hopefully I get some quality time tonight using 433Mhz radio for synchronization tonight.

Oh and I received my order , I look forward to test the Dual Monolithic Tone Decoder and compare it to the fft-results

New parts recieved, mostly capacitors and some IC´s