temp sensor reading high temp

I bought that 37 in 1 sunfounder sensor kit, and I was experimenting with the temperature sensor(it says 'keyes' and has three pins, on a black ic). I hooked up the +5, GND, and signal, and used an example temp code I got with a starter kit about a year ago. The temp is reading in the hundreds! Now the temp sensor that came with the kit is diferent from the keyes temp sensor. Or maybe the IC is marked wrong (wrong GND, or S)? not sure. Anyone have exprience with this? I dont want to blow up a sensor if I can help it. Thanks!

P.S. I rechecked the temp code, C and F. It seems good.

So i checked all of the temp sensors that came with the package. They all seem to read very high. Here is my temp code that came with my starter kit(note, that this is not my code, it was uploaded from the starter kits website and it did work with the temp sensor it came with):


Example sketch 07


  Use the "serial monitor" window to read a temperature sensor.
  The TMP36 is an easy-to-use temperature sensor that outputs
  a voltage that's proportional to the ambient temperature.
  You can use it for all kinds of automation tasks where you'd
  like to know or control the temperature of something.
  More information on the sensor is available in the datasheet:

  Even more exciting, we'll start using the Arduino's serial port
  to send data back to your main computer! Up until now, we've 
  been limited to using simple LEDs for output. We'll see that
  the Arduino can also easily output all kinds of text and data.
Hardware connections:

  Be careful when installing the temperature sensor, as it is
  almost identical to the transistors! The one you want has 
  a triangle logo and "TMP" in very tiny letters. The
  ones you DON'T want will have "222" on them.

  When looking at the flat side of the temperature sensor
  with the pins down, from left to right the pins are:
  5V, SIGNAL, and GND.
  Connect the 5V pin to 5 Volts (5V).
  Connect the SIGNAL pin to ANALOG pin 0.
  Connect the GND pin to ground (GND).

This sketch was written by SparkFun Electronics,
with lots of help from the Arduino community.
This code is completely free for any use.
Visit http://www.arduino.cc to learn about the Arduino.

Version 2.0 6/2012 MDG

// We'll use analog input 0 to measure the temperature sensor's
// signal pin.

const int temperaturePin = A0;

void setup()
  // In this sketch, we'll use the Arduino's serial port
  // to send text back to the main computer. For both sides to
  // communicate properly, they need to be set to the same speed.
  // We use the Serial.begin() function to initialize the port
  // and set the communications speed.
  // The speed is measured in bits per second, also known as
  // "baud rate". 9600 is a very commonly used baud rate,
  // and will transfer about 10 characters per second.

void loop()
  // Up to now we've only used integer ("int") values in our
  // sketches. Integers are always whole numbers (0, 1, 23, etc.).
  // In this sketch, we'll use floating-point values ("float").
  // Floats can be fractional numbers such as 1.42, 2523.43121, etc.

  // We'll declare three floating-point variables
  // (We can declare multiple variables of the same type on one line:)

  float voltage, degreesC, degreesF;

  // First we'll measure the voltage at the analog pin. Normally
  // we'd use analogRead(), which returns a number from 0 to 1023.
  // Here we've written a function (further down) called
  // getVoltage() that returns the true voltage (0 to 5 Volts)
  // present on an analog input pin.

  voltage = getVoltage(temperaturePin);
  // Now we'll convert the voltage to degrees Celsius.
  // This formula comes from the temperature sensor datasheet:

  degreesC = (voltage - 0.5) * 100.0;
  // While we're at it, let's convert degrees Celsius to Fahrenheit.
  // This is the classic C to F conversion formula:
  degreesF = degreesC * (9.0/5.0) + 32.0;
  // Now we'll use the serial port to print these values
  // to the serial monitor!
  // To open the serial monitor window, upload your code,
  // then click the "magnifying glass" button at the right edge
  // of the Arduino IDE toolbar. The serial monitor window
  // will open.

  // (NOTE: remember we said that the communication speed
  // must be the same on both sides. Ensure that the baud rate
  // control at the bottom of the window is set to 9600. If it
  // isn't, change it to 9600.)
  // Also note that every time you upload a new sketch to the
  // Arduino, the serial monitor window will close. It does this
  // because the serial port is also used to upload code!
  // When the upload is complete, you can re-open the serial
  // monitor window.
  // To send data from the Arduino to the serial monitor window,
  // we use the Serial.print() function. You can print variables
  // or text (within quotes).

  Serial.print("voltage: ");
  Serial.print("  deg C: ");
  Serial.print("  deg F: ");

  // These statements will print lines of data like this:
  // "voltage: 0.73 deg C: 22.75 deg F: 72.96"

  // Note that all of the above statements are "print", except
  // for the last one, which is "println". "Print" will output
  // text to the SAME LINE, similar to building a sentence
  // out of words. "Println" will insert a "carriage return"
  // character at the end of whatever it prints, moving down
  // to the NEXT line.
  delay(1000); // repeat once per second (change as you wish!)

float getVoltage(int pin)
  // This function has one input parameter, the analog pin number
  // to read. You might notice that this function does not have
  // "void" in front of it; this is because it returns a floating-
  // point value, which is the true voltage on that pin (0 to 5V).
  // You can write your own functions that take in parameters
  // and return values. Here's how:
    // To take in parameters, put their type and name in the
    // parenthesis after the function name (see above). You can
    // have multiple parameters, separated with commas.
    // To return a value, put the type BEFORE the function name
    // (see "float", above), and use a return() statement in your code
    // to actually return the value (see below).
    // If you don't need to get any parameters, you can just put
    // "()" after the function name.
    // If you don't need to return a value, just write "void" before
    // the function name.

  // Here's the return statement for this function. We're doing
  // all the math we need to do within this statement:
  return (analogRead(pin) * 0.004882814);
  // This equation converts the 0 to 1023 value that analogRead()
  // returns, into a 0.0 to 5.0 value that is the true voltage
  // being read at that pin.

// Other things to try with this code:

//   Turn on an LED if the temperature is above or below a value.

//   Read that threshold value from a potentiometer - now you've
//   created a thermostat!

if anyone sees a problem, please let me know!

The comment tells you that your temperature sensor must have the characters "TMP" on it, else it's not the temperature sensor but the transistor. Do you really have the kit that this comment mentions? Please provide a link to the kit you're using. The only temperature sensor module named "keyes" I found on the Net uses a temperature sensor from Dallas Semiconductor which communicates with the processor using the 1-Wire protocol. If you cannot find the link to the kit, make a (sharp) picture of your sensor to give us an impression of what you're using.

Pylon, yes, the sun founder kit does have Dallas on the temp sensors, and the starter kit I have, the temp says TMP. I did not know that would be a problem when hooking it up. I am still looking for more on 'Keyes'. But you were right.

The “voltage” variable in your program is not voltage.

The analog input returns a number between 0 and 1023, which corresponds to the voltage range from 0 to 5V.

If you want to determine the actual voltage, you need a calculation like

int analog_value = analogRead( temperaturePin ) ;
float volts = 5.0 * analog_value / 1024 ;