Faulty LM35, Arduino, power supply, or connection?

Other Hardware Sensors
1

Code and connections from:

https://www.instructables.com/Arduino-Temperature-Sensor-Using-LM35/

Power supply is using Asus's computer port.

LM35s are from China apparently.

Arduino UNO R3 is used.

Arduino IDE version 2.3.2 is used.

Result with just Arduino board:

|17:10:48.525 -> in DegreeC=|121.70 in Fahrenheit=|251.06|
|17:10:49.023 -> in DegreeC=|116.32 in Fahrenheit=|241.38|
|17:10:49.537 -> in DegreeC=|107.53 in Fahrenheit=|225.55|
|17:10:50.053 -> in DegreeC=|96.29 in Fahrenheit=|205.31|
|17:10:50.530 -> in DegreeC=|92.86 in Fahrenheit=|199.16|
|17:10:51.029 -> in DegreeC=|95.31 in Fahrenheit=|203.55|
|17:10:51.562 -> in DegreeC=|101.17 in Fahrenheit=|214.11|
|17:10:52.062 -> in DegreeC=|107.53 in Fahrenheit=|225.55|
|17:10:52.551 -> in DegreeC=|117.79 in Fahrenheit=|244.02|
|17:10:53.045 -> in DegreeC=|124.14 in Fahrenheit=|255.46|
|17:10:53.567 -> in DegreeC=|123.66 in Fahrenheit=|254.58|
|17:10:54.054 -> in DegreeC=|120.23 in Fahrenheit=|248.42|
|17:10:54.571 -> in DegreeC=|115.35 in Fahrenheit=|239.62|
|17:10:55.041 -> in DegreeC=|106.55 in Fahrenheit=|223.79|
|17:10:55.562 -> in DegreeC=|95.80 in Fahrenheit=|204.43|
|17:10:56.077 -> in DegreeC=|92.38 in Fahrenheit=|198.28|
|17:10:56.546 -> in DegreeC=|94.82 in Fahrenheit=|202.67|
|17:10:57.061 -> in DegreeC=|99.71 in Fahrenheit=|211.47|
|17:10:57.579 -> in DegreeC=|106.55 in Fahrenheit=|223.79|
|17:10:58.069 -> in DegreeC=|115.35 in Fahrenheit=|239.62|
|17:10:58.566 -> in DegreeC=|123.66 in Fahrenheit=|254.58|
|17:10:59.067 -> in DegreeC=|125.12 in Fahrenheit=|257.22|
|17:10:59.554 -> in DegreeC=|121.70 in Fahrenheit=|251.06|

Result with LM35:

|17:16:09.950 -> in DegreeC=|0.00 in Fahrenheit=|32.00|
|17:16:10.436 -> in DegreeC=|0.00 in Fahrenheit=|32.00|
|17:16:10.934 -> in DegreeC=|0.00 in Fahrenheit=|32.00|
|17:16:11.439 -> in DegreeC=|0.00 in Fahrenheit=|32.00|
|17:16:11.957 -> in DegreeC=|0.00 in Fahrenheit=|32.00|
|17:16:12.458 -> in DegreeC=|2.93 in Fahrenheit=|37.28|
|17:16:12.960 -> in DegreeC=|25.42 in Fahrenheit=|77.75|
|17:16:13.458 -> in DegreeC=|37.15 in Fahrenheit=|98.86|
|17:16:13.940 -> in DegreeC=|38.61 in Fahrenheit=|101.50|
|17:16:14.452 -> in DegreeC=|36.17 in Fahrenheit=|97.10|
|17:16:14.956 -> in DegreeC=|32.26 in Fahrenheit=|90.06|
|17:16:15.446 -> in DegreeC=|20.53 in Fahrenheit=|68.95|
|17:16:15.962 -> in DegreeC=|3.42 in Fahrenheit=|38.16|
|17:16:16.461 -> in DegreeC=|0.00 in Fahrenheit=|32.00|
|17:16:16.977 -> in DegreeC=|0.00 in Fahrenheit=|32.00|
|17:16:17.482 -> in DegreeC=|0.00 in Fahrenheit=|32.00|
|17:16:17.960 -> in DegreeC=|0.00 in Fahrenheit=|32.00|
|17:16:18.478 -> in DegreeC=|0.00 in Fahrenheit=|32.00|
|17:16:18.981 -> in DegreeC=|15.64 in Fahrenheit=|60.15|
|17:16:19.466 -> in DegreeC=|36.17 in Fahrenheit=|97.10|
|17:16:19.984 -> in DegreeC=|37.63 in Fahrenheit=|99.74|
|17:16:20.468 -> in DegreeC=|38.12 in Fahrenheit=|100.62|
|17:16:20.987 -> in DegreeC=|33.72 in Fahrenheit=|92.70|
|17:16:21.487 -> in DegreeC=|27.37 in Fahrenheit=|81.27|
|17:16:21.991 -> in DegreeC=|12.22 in Fahrenheit=|53.99|
|17:16:22.463 -> in DegreeC=|0.00 in Fahrenheit=|32.00|
|17:16:22.994 -> in DegreeC=|0.00 in Fahrenheit=|32.00|
|17:16:23.477 -> in DegreeC=|0.00 in Fahrenheit=|32.00|
|17:16:23.969 -> in DegreeC=|0.00 in Fahrenheit=|32.00|
|17:16:24.478 -> in DegreeC=|0.00 in Fahrenheit=|32.00|
|17:16:24.971 -> in DegreeC=|2.93 in Fahrenheit=|37.28|
|17:16:25.475 -> in DegreeC=|28.35 in Fahrenheit=|83.03|
|17:16:25.974 -> in DegreeC=|37.15 in Fahrenheit=|98.86|
|17:16:26.492 -> in DegreeC=|38.61 in Fahrenheit=|101.50|
|17:16:27.006 -> in DegreeC=|36.17 in Fahrenheit=|97.10|
|17:16:27.490 -> in DegreeC=|32.26 in Fahrenheit=|90.06|
|17:16:27.982 -> in DegreeC=|20.53 in Fahrenheit=|68.95|
|17:16:28.481 -> in DegreeC=|3.91 in Fahrenheit=|39.04|

2

As the output seems fluctuating with 5 consecutive zero-values, it looks to me like either some E/M interference or a bad cabling.
We're talking about millivolts, so I hope you checked the cabling (make sure you're using good quality cables and a good breadboard with no oxidations) and you don't have any device emitting interferences like a cell phone, WiFi, transformers, mains wires, or anything else next to the circuit.

After those checks, if everything fails, it could be a faulty LM35, try another one if you have it.

1 Like
3

Post a picture of your setup. But first try twisting the sensor wires. How long are the sensor wires?

4

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