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MLX90621 hardware

Posted: Wed Jun 21, 2017 9:27 am
by GGL
Hello everybody,
Someone has experience with "Melexis MLX90621 (16x4 IR array) + Micropython" board?
I want to make a "human body detection" (presence detector).

Thanks in advance.

Re: MLX90621 hardware

Posted: Wed Jun 21, 2017 4:36 pm
by deshipu
This is oddly specific. I don't have any experience with this particular sensor, but looking at the datasheet at https://www.melexis.com/en/product/MLX9 ... -Low-Noise is seems that it should be relatively easy to implement an I²C driver for communicating with it. However, it seems that its principle of operation is not trivial, and while you can get the data from it easily, actually doing something useful with that data (and before that, calibrating the sensor properly) may be an art of its own. In any case, it should be doable.

Re: MLX90621 hardware

Posted: Wed Jun 21, 2017 4:37 pm
by deshipu
On the other hand, have you looked at the simple PIR sensors? They could detect human presence much easier.

Re: MLX90621 hardware

Posted: Wed Jun 21, 2017 10:52 pm
by wminarik
Over at OpenMV they have a thermal shield that uses the MLX90621:
https://openmv.io/collections/shields/p ... ile-shield
with the Micropython code in their GitHub repository:
https://github.com/openmv

I've used the MLX90621 with the code and it works well.

Re: MLX90621 hardware

Posted: Thu Jun 22, 2017 6:48 am
by GGL
Thanks for yours answers and opinions.
deshipu: In my case the PIR sensor is not be able, because I need detect the presence of human body, and the PIR only detect movement through the temperature changes.
wminarik: I will check the OPEN MV project, but I think that this solution (OPEN MV camera + MLX90621 module), is expensive for me.

Thanks.

Re: MLX90621 hardware

Posted: Thu Jun 22, 2017 7:47 am
by pythoncoder
The thermal shield info says "This product is no longer sold any more.". However the OpenMV cam has an IR LED so it should be able to do presence detection in the dark simply and in MicroPython.

But I'm with @deshipu on this: PIR sensors are the security industry standard way to do the job.

Re: MLX90621 hardware

Posted: Thu Jun 22, 2017 8:04 am
by GGL
Thanks pythoncoder,
I'll check about OpenMV CAM with IR LED solution.

Re: MLX90621 hardware

Posted: Thu Jun 22, 2017 10:57 am
by Roberthh
To act just as a motion detection, a PIR sensor is sufficient. I tried a few, and ended up using sensors of the AMN-Series of Panasonic (e.g. AMN31111J). A little bit more expensive than the usual 4-6$ models from China, but very easy to integrate (Vcc 3..6V, open drain output), many different variants and very reliable.
But this device here aims at a precise measurement of the temperature, and that makes it different to the usual PIR sensor, and opens other use cases. But I see, the price is ~45€ in low quantities.

Re: MLX90621 hardware

Posted: Fri Jun 23, 2017 1:05 am
by mcauser
If you need penetration through plastic, walls, etc, have a look at some of the cheap doppler microwave sensors now available.
eg. HB-100, HW-MS03, WB3-12, XYC-WB-D, HFS-DC06, RCWL-9196 and RCWL-0516

They operate on 2.4GHz, 5.8GHz or 10.5GHz, so watch out for wifi interference.

The guy with the Swiss accent (Andreas Spiess) has a comparison video:
https://www.youtube.com/watch?v=9WiJJgIi3W0

Roger Clark reviews RCWL-9196 and RCWL-0516 radars:
http://www.rogerclark.net/investigating ... r-modules/

Re: MLX90621 hardware

Posted: Tue Jun 27, 2017 10:54 am
by GGL
Thaks at all,
Roberthh: I will check the "AMN-Series of Panasonic"
mcauser: thank you for another line of instruments (doppler microwave)