Jp3141
Well-known member
This uses a Teensy 3.2 and its FTM to precisely measure the frequency of the AC power line. An external GPS provides a 1 pps calibration pulse to continuously calibrate the Teensy's 48 MHz clock. Data is logged via a Raspberry Pi 0 W. A 9 V AC adapter powers the system and also provides the 60 Hz signal which is measured.
This project uses multiple FTM channels -- one for the 60 Hz, and one for the 1 pps calibration.
The Teensy's comparator and DAC are used to sense the 60 Hz signal. The comparator provides a clean output, and its hysteresis prevents false signals. Data is transmitted via the Teensy's USB serial (if connected), and to the R Pi's serial port for it to log via WiFi. A tri-color LED is also provides pulses for a visual indication of correct operation.
For simplicity and debugging, all modules are mounted on a 3-D printed base with brass inserts to hold the GPS and R Pi boards. A small perf. board holds the R.C filter for the raw 60 Hz AC signal.
The system is very accurate (synchronized to GPS 1 pps which is +/- 20 ns) and has high resolution -- it is easy to see 0.0001 Hz frequency shifts which continually occur. The R Pi logging also prints a simple strip chart. An example of logged output is:
and the terminal log looks like:
Code is on Github at https://github.com/jp3141/60Hz
This project uses multiple FTM channels -- one for the 60 Hz, and one for the 1 pps calibration.
The Teensy's comparator and DAC are used to sense the 60 Hz signal. The comparator provides a clean output, and its hysteresis prevents false signals. Data is transmitted via the Teensy's USB serial (if connected), and to the R Pi's serial port for it to log via WiFi. A tri-color LED is also provides pulses for a visual indication of correct operation.
For simplicity and debugging, all modules are mounted on a 3-D printed base with brass inserts to hold the GPS and R Pi boards. A small perf. board holds the R.C filter for the raw 60 Hz AC signal.
The system is very accurate (synchronized to GPS 1 pps which is +/- 20 ns) and has high resolution -- it is easy to see 0.0001 Hz frequency shifts which continually occur. The R Pi logging also prints a simple strip chart. An example of logged output is:
Code:
2022-02-01 19:11:51.738 #
2022-02-01 19:11:51.738 # Ticks, Cycles, Frequency, FBUS, Total Cyc, Flt, Phase, 1Hz
2022-02-01 19:11:51.801 2405375, 3, 59.864714234, 47999029, 3, 16, 69, 584
2022-02-01 19:11:55.001 153609267, 192, 59.995167870, 47999030, 195, 16, 60, 731
2022-02-01 19:12:00.005 240812523, 301, 59.995666127, 47999029, 496, 16, 53, 11
2022-02-01 19:12:05.005 239999487, 300, 59.998914498, 47999029, 796, 16, 51, 11
2022-02-01 19:12:10.005 239989904, 300, 60.001311555, 47999030, 1096, 16, 53, 10
2022-02-01 19:12:15.001 239181069, 299, 60.003535108, 47999029, 1395, 16, 57, 731
2022-02-01 19:12:20.005 240795819, 301, 59.999828024, 47999029, 1696, 16, 60, 10
2022-02-01 19:12:25.005 239983561, 300, 60.002896198, 47999029, 1996, 16, 65, 10
2022-02-01 19:12:30.001 239182315, 299, 60.003223775, 47999030, 2295, 16, 70, 731
2022-02-01 19:12:35.001 239984842, 300, 60.002575913, 47999029, 2595, 16, 75, 730
2022-02-01 19:12:40.001 239991266, 300, 60.000971035, 47999030, 2895, 16, 77, 730
2022-02-01 19:12:45.005 240802031, 301, 59.998281451, 47999030, 3196, 16, 74, 10
2022-02-01 19:12:50.005 240022253, 300, 59.993224878, 47999030, 3496, 16, 62, 10
2022-02-01 19:12:55.001 239255002, 299, 59.984994462, 47999030, 3795, 16, 41, 732and the terminal log looks like:
Code:
2022-02-13 17:00:15.005 239843216, 300, 60.037983313, 47999010, 4314584, 16, 221, 5, -·························0·························>
2022-02-13 17:00:20.005 239844227, 300, 60.037730239, 47999010, 4314884, 16, 289, 3, -·························0·························>
2022-02-13 17:00:25.005 240669121, 301, 60.031390608, 47999010, 4315185, 16, 345, 13, -·························0·························>
2022-02-13 17:00:30.005 239857633, 300, 60.034373390, 47999009, 4315485, 16, 47, 11, -·························0·························>
2022-02-13 17:00:35.005 239865623, 300, 60.032374877, 47999010, 4315785, 16, 105, 9, -·························0·························>
2022-02-13 17:00:40.005 239876040, 300, 60.029766624, 47999009, 4316085, 16, 159, 8, -·························0·························>
2022-02-13 17:00:45.005 239885975, 300, 60.027281712, 47999010, 4316385, 16, 208, 6, -·························0·························>
2022-02-13 17:00:50.005 239895164, 300, 60.024982413, 47999010, 4316685, 16, 253, 4, -·························0························/+
2022-02-13 17:00:55.005 239904306, 300, 60.022693799, 47999009, 4316985, 16, 294, 3, -·························0······················/··+
2022-02-13 17:01:00.005 240724393, 301, 60.017605731, 47999009, 4317286, 16, 326, 13, -·························0·················/·······+
2022-02-13 17:01:05.005 239941945, 300, 60.013278212, 47999009, 4317586, 16, 349, 12, -·························0············/············+
2022-02-13 17:01:10.005 239954304, 300, 60.010187190, 47999009, 4317886, 16, 8, 12, -·························0·········/···············+
2022-02-13 17:01:15.005 239969684, 300, 60.006339801, 47999008, 4318186, 16, 19, 11, -·························0·····/···················+
2022-02-13 17:01:20.005 239957446, 300, 60.009400167, 47999008, 4318486, 16, 36, 11, -·························0········\················+
2022-02-13 17:01:25.005 239938790, 300, 60.014067338, 47999009, 4318786, 16, 61, 10, -·························0·············\···········+
2022-02-13 17:01:30.005 239920783, 300, 60.018571630, 47999009, 4319086, 16, 95, 9, -·························0··················\······+
2022-02-13 17:01:35.005 239901348, 300, 60.023433882, 47999009, 4319386, 16, 137, 8, -·························0······················\··+
2022-02-13 17:01:40.005 239883628, 300, 60.027867763, 47999009, 4319686, 16, 187, 6, -·························0·························>
2022-02-13 17:01:45.005 239875502, 300, 60.029900010, 47999008, 4319986, 16, 241, 4, -·························0·························>
2022-02-13 17:01:50.005 239866520, 300, 60.032147880, 47999008, 4320286, 16, 299, 2, -·························0·························>
2022-02-13 17:01:55.005 240648454, 301, 60.036543630, 47999008, 4320587, 16, 5, 12, -·························0·························>
2022-02-13 17:02:00.005 239866335, 300, 60.032194180, 47999008, 4320887, 16, 63, 10, -·························0·························>
2022-02-13 17:02:05.005 239910492, 300, 60.021143636, 47999007, 4321187, 16, 101, 9, -·························0····················/····+
2022-02-13 17:02:10.005 239931536, 300, 60.015880530, 47999008, 4321487, 16, 129, 8, -·························0···············/·········+
2022-02-13 17:02:15.005 239927933, 300, 60.016781789, 47999008, 4321787, 16, 159, 7, -·························0················\········+
2022-02-13 17:02:20.005 239914527, 300, 60.020134171, 47999007, 4322087, 16, 196, 6, -·························0···················\·····+
2022-02-13 17:02:25.005 239912040, 300, 60.020757608, 47999008, 4322387, 16, 233, 5, -·························0····················\····+
2022-02-13 17:02:30.005 239944270, 300, 60.012695448, 47999008, 4322687, 16, 256, 4, -·························0············/············+
2022-02-13 17:02:35.005 239962056, 300, 60.008247304, 47999008, 4322987, 16, 271, 3, -·························0·······/·················+
2022-02-13 17:02:40.005 239972842, 300, 60.005548878, 47999007, 4323287, 16, 281, 3, -·························0·····/···················+
2022-02-13 17:02:45.005 239944460, 300, 60.012647927, 47999008, 4323587, 16, 304, 2, -·························0············\············+Code is on Github at https://github.com/jp3141/60Hz
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