I am starting to play with the TMP36 sensor from the start kit.
Datasheet is here : https://www.arduino.cc/en/uploads/Main/TemperatureSensor.pdf
My understanding is ok with the power voltage (2,7 to 5,5v) and the output voltage to get the temperature value.
However, I am wondering if I have to add a resistor to the circuit to protect the sensor. We can find in the datasheet we must stay between 2,7 and 5,5v supply voltage but nothing regarding the supply current.
I have just find a supply voltage 'unloaded' which is 50uA. With a 5v voltage supply it means i would need a 105 resistor which is hugeeeee.. I think i am missing something.
ExploreBen:
it means i would need a 105 resistor which is hugeeeee..
No, a 100M is a large resistor value, 100k is commonplace, as is pretty much anything between
1 ohm and 1M - except for digital logic where you only normally need 220 ohm (LEDs) and 10k
(pullups).
MarkT:
No, a 100M is a large resistor value, 100k is commonplace, as is pretty much anything between
1 ohm and 1M - except for digital logic where you only normally need 220 ohm (LEDs) and 10k
(pullups).
Thx ! So would you confirm we should use a 100K resistor with a TMP36 to have a clean set up ? In all the tutorials I have seen it is used with no resistors. I am trying to understand why (it is pretty clear in terms of voltage but not in terms of current)
Forget about resistors. Resistors in the power line could make the device unstable (oscillate).
The sensor just draws the current it needs, and that is loooow (to prevent self-heating).
Power it from the 3.3volt pin (assuming you have an Uno), for a 'cleaner' sensor supply.
Don't worry about destroying your sensor (be happy if you do).
One day you will stop using analogue sensors like the LM35 or TMP36.
Digital sensors, like the DS18B20, are more stable, have a higher resolution, and are easier to work with.
Leo..
ExploreBen:
Hi again !
Many thanks for your replies.
Yep alright but it does not explain why
Thx ! So would you confirm we should use a 100K resistor with a TMP36 to have a clean set up ?
No, that is not what I said, I just said 100k is not a large value for a resistor. Read the datasheet for
the TMP36 if you want to see how to use it - that's what we do to answer your question - reading
datasheets is really important skill to acquire, read lots of them!
Wawa:
Forget about resistors. Resistors in the power line could make the device unstable (oscillate).
The sensor just draws the current it needs, and that is loooow (to prevent self-heating).
Power it from the 3.3volt pin (assuming you have an Uno), for a 'cleaner' sensor supply.
MarkT:
No, that is not what I said, I just said 100k is not a large value for a resistor. Read the datasheet for
the TMP36 if you want to see how to use it - that's what we do to answer your question - reading
datasheets is really important skill to acquire, read lots of them!
Regarding these quotes, I think this part of the datasheet may help :
" The supply current runs well below 50 µA, providing very low self-heating—less than 0.1°C in still air. In addition, a shutdown function is provided to cut the supply current to less than 0.5 µA"
So the component is able to use the current it needs (as Wawa said) and manage the excess through the shutdown function. Ideally it would be great to understand how the component is able to control the current used but it might be too sharp for me regarding my knowledge as of now.
