Beacon Sensing
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The circuit we built to sense a 5 kHz home beacon included a high-pass filter, an op-amp (L324) gain stage to increase the amplitude of the IR signal, and a Schmitt trigger using a comparator (L339) to clean the final signal up before inputting it to a tone decoder set to a mean frequency of 5 kHz. The whole circuit had a virtual ground set at around 1.75V to prevent railing at any op-amps after our gain stage. Using a tone decoder tuned to only sense a signal close to 5 kHz was incredibly helpful and accurate. The decoder chip required minimal calculations and wiring and reduced the need to filter out the 1 kHz signal through code to our Arduino. The fifth harmonic of a 1 kHz signal can be tricky to code around, but the decoder eliminated this problem. |
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The only problem we encountered with our IR circuit came about a week after making a functional circuit, when an unusual signal arose from our photo transistor providing the IR signal. The problem was probably from a broken breadboard or possibly the use of polar capacitors on our decoder at first and them decaying over time. After switching to a new breadboard and changing to non-polarized. Below schematic.
| 5khz_ir_sensor.sch |
