const char* ssid = "HG8145V5_3D80E";
const char* pass = "rSCvg92E";
const char topic[] = "motor";
WiFiClient net;
MQTTClient client;
const int sensitivity = -58;
const int gain = 20;
const int sensorPIN = A0;
const int sampleWindow = 1000;
unsigned int sample;
unsigned long lastMillis = 0;
void connect() {
Serial.print("checking wifi...");
while (WiFi.status() != WL_CONNECTED) {
Serial.print(".");
delay(1000);
}
Serial.print("\nconnecting...");
while (!client.connect(DEV_NAME, MQTT_USER, MQTT_PW)) {
Serial.print(".");
delay(1000);
}
Serial.println("\nconnected!");
client.subscribe("\mqtt_table_1"); //SUBSCRIBE TO TOPIC /hello
}
void messageReceived(String &topic, String &payload) {
Serial.println("incoming: " + topic + " - " + payload);
}
void setup()
{
Serial.begin(9600);
WiFi.begin(ssid, pass);
client.begin(BROKER_IP, 1883, net);
//client.onMessage(messageReceived);
connect();
}
void loop()
{
client.loop();
if (!client.connected()) {
connect();
}
unsigned long startMillis= millis();
unsigned int peakToPeak = 0;
unsigned int signalMax = 0;
unsigned int signalMin = 1024;
// collect data for Sample window width in mS
while (millis() - startMillis < sampleWindow)
{
sample = analogRead(sensorPIN);
if (sample < 1024)
{
if (sample > signalMax)
{
signalMax = sample;
}
else if (sample < signalMin)
{
signalMin = sample;
}
}
}
peakToPeak = signalMax - signalMin;
double volts = ((peakToPeak * 5.0) / 1024)*10;
double volts_db = 20*log10(volts/0.001259);
double spl_db = volts_db + 94 + sensitivity - gain;
String dB_mqtt = String(spl_db, 2);
if (millis() - lastMillis > 1000) {
lastMillis = millis();
String dB_mqtt = String(spl_db, 2);
client.publish("mqtt_table_1", dB_mqtt);
}
Serial.print("sample: " + String(sample) );
Serial.print("\t");
Serial.print("signalMax: " + String(signalMax) );
Serial.print("\t");
Serial.print("signalMin: " + String(signalMin) );
Serial.print("\t");
Serial.print("peakToPeak: " + String(peakToPeak) );
Serial.print("\t");
Serial.print("volts: " + String(volts) );
Serial.print("\t"); // prints a tab
Serial.print("dB: " + String(volts_db) );
Serial.print("\t");
Serial.println("dB-spl: " + String(spl_db) );
}
```
Here is the output
```auto
15:16:33.088 -> sample: 522 signalMax: 1023 signalMin: 0 peakToPeak: 1023 volts: 49.95 dB: 91.97 dB-spl: 107.97
15:16:34.104 -> sample: 509 signalMax: 1023 signalMin: 0 peakToPeak: 1023 volts: 49.95 dB: 91.97 dB-spl: 107.97
15:16:35.142 -> sample: 502 signalMax: 1023 signalMin: 0 peakToPeak: 1023 volts: 49.95 dB: 91.97 dB-spl: 107.97
15:16:36.136 -> sample: 508 signalMax: 1023 signalMin: 0 peakToPeak: 1023 volts: 49.95 dB: 91.97 dB-spl: 107.97
15:16:37.170 -> sample: 513 signalMax: 1023 signalMin: 0 peakToPeak: 1023 volts: 49.95 dB: 91.97 dB-spl: 107.97
15:16:38.209 -> sample: 660 signalMax: 1023 signalMin: 0 peakToPeak: 1023 volts: 49.95 dB: 91.97 dB-spl: 107.97
15:16:39.244 -> sample: 534 signalMax: 1023 signalMin: 0 peakToPeak: 1023 volts: 49.95 dB: 91.97 dB-spl: 107.97
```
---
### Author:  [@knolleary](https://discourse.nodered.org/u/knolleary)
#### Post date: [16 November 2021 08:05 UTC](https://discourse.nodered.org/t/why-the-signalmin-is-always-0/53806/2 "2021-11-16T08:05:40Z")
> [@jhunnx](#):
>
> `sample`
In that code `sample` is set by a call to `analogRead`, meaning its value will be between 0 and 1024.
`sigMin` is initialised with the value `0`.
It only gets changed if `sample` is smaller - which it never will be.
The fix is to initialise `sigMin` to `1024` so that it starts bigger than any possible value of `sample`.
---
### Author:  [@jhunnx](https://discourse.nodered.org/u/jhunnx)
#### Post date: [16 November 2021 08:24 UTC](https://discourse.nodered.org/t/why-the-signalmin-is-always-0/53806/3 "2021-11-16T08:24:35Z")
Thank you for pointing it out i missed that one.
I dont know really why but i still got same output the signalMin still at 0
---
### Author:  [@knolleary](https://discourse.nodered.org/u/knolleary)
#### Post date: [16 November 2021 08:34 UTC](https://discourse.nodered.org/t/why-the-signalmin-is-always-0/53806/4 "2021-11-16T08:34:18Z")
> [@jhunnx](#):
>
> `else if (sample < signalMin)`
Get rid of the `else` in the above line.
---
### Author:  [@jhunnx](https://discourse.nodered.org/u/jhunnx)
#### Post date: [16 November 2021 09:37 UTC](https://discourse.nodered.org/t/why-the-signalmin-is-always-0/53806/5 "2021-11-16T09:37:44Z")
I removed it and still the same output. Maybe there is some interuption in my code after i integrated the mqtt?
---
### Author:  [@knolleary](https://discourse.nodered.org/u/knolleary)
#### Post date: [16 November 2021 09:57 UTC](https://discourse.nodered.org/t/why-the-signalmin-is-always-0/53806/6 "2021-11-16T09:57:18Z")
The output you have shows `signalMax` is always 1023 and `signalMin` is always 0. There must be some flaw in the logic, but at this point, I can't see anything obvious. The MQTT part won't be changing the local variables.
At this point I would add some more debug inside the `while` loop to check what is actually happening.
---
### Author:  [@jhunnx](https://discourse.nodered.org/u/jhunnx)
#### Post date: [16 November 2021 12:36 UTC](https://discourse.nodered.org/t/why-the-signalmin-is-always-0/53806/7 "2021-11-16T12:36:13Z")
Thank you very much. I really appreciate it
---
### Author:  [@system](https://discourse.nodered.org/u/system)
#### Post date: [15 January 2022 12:36 UTC](https://discourse.nodered.org/t/why-the-signalmin-is-always-0/53806/8 "2022-01-15T12:36:44Z")
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