It’s working.
I may be having a problem with my hot tub pump – it’s running with shorter cycles than I remember it. That’s better for close temperature control, but worse for stress on the motor.
I had a problem with the pump’s computer unit once before – it was overheating and cycling more and more rapidly. So now I want to monitor it to see if its cycling is getting faster.
I can’t monitor it using a current sensor, since those ones I have are rated for 10A at 120V, while the motor unit uses 15A at 120V.
So I built a monitoring system – weather sealed a 1″ piezo disk, breadboarded a JFET amplifier for it, connected it to an ESP8266 microcontroller which I programmed to take readings at 480Hz, dot-product out the components at 60Hz and 120Hz (which for some reason is stronger) and send them via WiFi to my MQTT server, from which I scoop them with a Perl script to a log file (for now). I’ve determined the best discriminant between non-running and running with a z-score of 6.6+ from each, so I know it’s pretty good.
Now I can relax for a while while the data accumulates…
Data from the 60Hz and 120Hz dot-products:
7-Dec-2021 14:02:18: home/hot_tub_motor/a02/value/couplet -> 32.839 16.014 7-Dec-2021 14:02:24: home/hot_tub_motor/a02/value/couplet -> 29.103 16.061 7-Dec-2021 14:02:29: home/hot_tub_motor/a02/value/couplet -> 29.301 16.638 7-Dec-2021 14:02:35: home/hot_tub_motor/a02/value/couplet -> 32.062 17.769 7-Dec-2021 14:02:40: home/hot_tub_motor/a02/value/couplet -> 28.854 16.440 7-Dec-2021 14:02:45: home/hot_tub_motor/a02/value/couplet -> 33.069 16.328 7-Dec-2021 14:02:51: home/hot_tub_motor/a02/value/couplet -> 28.665 17.092 7-Dec-2021 14:02:56: home/hot_tub_motor/a02/value/couplet -> 28.019 18.892 7-Dec-2021 14:03:03: home/hot_tub_motor/a02/value/couplet -> 32.541 17.647 7-Dec-2021 14:03:07: home/hot_tub_motor/a02/value/couplet -> 29.323 16.411 7-Dec-2021 14:03:12: home/hot_tub_motor/a02/value/couplet -> 69.411 58.708 7-Dec-2021 14:03:17: home/hot_tub_motor/a02/value/couplet -> 38.942 56.288 7-Dec-2021 14:03:24: home/hot_tub_motor/a02/value/couplet -> 16.419 50.588 7-Dec-2021 14:03:32: home/hot_tub_motor/a02/value/couplet -> 25.903 59.193 7-Dec-2021 14:03:33: home/hot_tub_motor/a02/value/couplet -> 70.220 61.097 7-Dec-2021 14:03:40: home/hot_tub_motor/a02/value/couplet -> 60.011 61.728 7-Dec-2021 14:03:44: home/hot_tub_motor/a02/value/couplet -> 17.743 51.550 7-Dec-2021 14:03:49: home/hot_tub_motor/a02/value/couplet -> 37.571 57.612 7-Dec-2021 14:03:55: home/hot_tub_motor/a02/value/couplet -> 72.898 57.997 7-Dec-2021 14:04:00: home/hot_tub_motor/a02/value/couplet -> 23.630 55.861 7-Dec-2021 14:04:06: home/hot_tub_motor/a02/value/couplet -> 41.698 62.395 7-Dec-2021 14:04:11: home/hot_tub_motor/a02/value/couplet -> 56.960 59.568 7-Dec-2021 14:04:18: home/hot_tub_motor/a02/value/couplet -> 15.589 50.445 7-Dec-2021 14:04:22: home/hot_tub_motor/a02/value/couplet -> 71.046 62.314 7-Dec-2021 14:04:27: home/hot_tub_motor/a02/value/couplet -> 16.098 46.108 7-Dec-2021 14:04:32: home/hot_tub_motor/a02/value/couplet -> 70.857 61.175 7-Dec-2021 14:04:39: home/hot_tub_motor/a02/value/couplet -> 16.661 53.204 7-Dec-2021 14:04:45: home/hot_tub_motor/a02/value/couplet -> 73.267 63.262 7-Dec-2021 14:04:48: home/hot_tub_motor/a02/value/couplet -> 14.290 54.907 7-Dec-2021 14:04:54: home/hot_tub_motor/a02/value/couplet -> 70.185 61.067 7-Dec-2021 14:05:01: home/hot_tub_motor/a02/value/couplet -> 22.880 57.029 7-Dec-2021 14:05:06: home/hot_tub_motor/a02/value/couplet -> 51.657 55.721 7-Dec-2021 14:05:10: home/hot_tub_motor/a02/value/couplet -> 47.116 61.623
The hot tub motor started up at 14:03:12.
Data discriminated into “off” and “on”:
About to subscribe to topic 'home/hot_tub_motor/a02/status' 7-Dec-2021 14:42:21: home/hot_tub_motor/a02/status -> 0 7-Dec-2021 14:52:23: home/hot_tub_motor/a02/status -> 1 7-Dec-2021 15:03:02: home/hot_tub_motor/a02/status -> 0
I’m not sure why the vibration is at 120Hz and not at 60Hz. I’ll have to think about AC motors and how they operate now.
Yay! Another investigation!