So I happen to have a TMP36 and decided to implement the temperature reading example. I connected it exactly as shown in the documentation, but I’m getting inaccurate readings. Whether I use a function, a variable or Serial.print I get values around 946. Using the method to convert this to voltage: …

Took some readings. Between 3V3* and GND = 3.28V Between 3V3* and A0 (with the TMP36 NOT connected) = 0.01V Between 3V3* and A0 (with the TMP36 connected) = 2.575V Between GND and output of TMP36 (NOT connected to A0) = 0.731V (Which converts to the right temperature) Between GND and output of …

I’m getting much the same thing. I measure the actual voltage across ground and the the 3.3* as 3.26V. The voltage on the signal line of the TMP36 is 0.68, corresponding to 18C, which is about right. However, I’ve recorded readings on A0 that have fluctuated between 836 and 1241 more or less random…

From my calculations, the difference between 3.3V and 3.28V is about 1°C, assuming the same reading on A0. Using your code exactly: int reading = 0; void setup() { Serial.begin(9600); Spark.variable("reading", &reading, INT); Spark.function("takeReading", takeReading); pinMode(A…

I had the same, also noticed tinker gives different readings to analogRead().

I’ve also noticed this. ~790 versus ~1270 with the same TMP36 setup. I did a voltage divider with two 1% 10k resistors and got 2096 +/- 5 which is what you’d expect.

@BDub I added a .1uf ceramic cap across pins 1 and 3 of the TMP36 as suggested, but it doesn’t produce any difference.

Thanks @Hypnopompia . I really wish I had one of those sensors to try it myself… The datasheet says it has a low output impedance so it really should work. I think I might have an LM34 which is a 10mV/°F sensor but it runs off of 5V so it might work, but might not really be apples to apples compar…

@BDub I actually did buy these from sparkfun. Same product you linked. TMP36GZ #1304 542733 (glad I had a magnifying glass handy - geez) :wink:

Ok this one is still puzzling, but here are some observations/questions: Looks like the TMP36GZ is rated for +/- 3°C accuracy at 25°C. So it's possible to be off by that 3°C without any voltage reading error. [image] Hypnopompia: Between GND and output of TMP36 (connected to A0) = 0.731V T…

Odd analog readings [SOLVED]

Troubleshooting

BDub December 28, 2013, 9:40pm 12

@Hypnopompia @wgbartley @DougC @gin if you have access to some capacitors would you please try this out and let me know if it improves the readings?

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Odd analog readings [SOLVED]

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