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Author Topic: Heat detection with thermopile sensors/non-contact / NEWBIE  (Read 1306 times)
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Vienna
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I have to detect heat in the range of approx. 50° C and a distance between 10 - 30 cm. I have already read the options TPA81 and Melexis MLX90614-boards with their price between 40 - 80 €. 

Is there a possibility to connect only a TPS334 (thermopile sensor) or MLX90614ESF-AAA components ? They should give a return value (voltage!) for my analog-input (or with i2c?), in the program I will convert this value into a approx. temperature. Has anybody experience with such a (cheaper) approach ?

Thanks in regard
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you've picked a bit of a tough one.  Do you need to detect temperature in absolute value or only a change in heat?  I think the TPA81 will only detect a moving/changing  heat signature.

I have some experience with this device:
"Parallax MLX90614 Infrared Thermometer Module (10° FOV)"

I have it working; it talks over serial RS232 to Arduino.  The only problem I have is that the Emissivity value cannot be changed.  I guess one other issue is that this solution is a bit expensive.

A nice solution (if you can figure it out) would be to use this device: MLX90614ESF-AAA and communicate through I2C.  However, the device technically is SMBUS (not I2C) and some references say it will work while others say it will not.  The best answer I found is that it is more compatible at 3.3V than 5V due to logic level differences.  For an example of this check out Sparkfun.  They have made a board that includes the Melexis sensor and some type of AVR chip to help us it.  I find the communication protocol with the MLX90614 very confusing but if Sparkfun has included the code with their board you will have a head start.


There is also some information on diydrones.com
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Vienna
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thanks a lot. I have to detect this hotter space, the temperature is not relevant. Therefore I thought there works simply components like fotoresistors...
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Since you have some experience with the 10 deg FOV sensor, do u know which material is the extra housing.

The 35/10 deg FOV sensors have an extra housing on top of the 90 deg FOV, but i simply cannot find what it is made of.

Thanks
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sorry, I cannot be certain about the plastic.   It might be Nylon or Delrin.  The datasheet doesn't say and I don't want to set mine on fire to find out what it is smiley-eek-blue
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Ok, so you are sure it is some plastic like nylon.
I was thinking that the housing should be done in a highly conductive metal, like copper, so that it would be easier to avoid temperature gradients, and to achieve a faster equilibrium temperature with the underneath sensor.

Also, won´t nylon be a problem if it warms up, due to its high emissivity?

BR
pnu
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