Exhaust gases multi-band air quality sensor on arduino - part 2

It's almost year has left after I had done my air quality monitor on Arduino.
During this year I have had a lot of accidents and adventures, but now I'm ready to return to blogging.

After successful master's dissertation defense and further graduation I have collected a lot of materials and data to write a couple science papers, but... but I still have no time to do this (moreover, some aspects of Ukrainian science are frustrating me so much), so I would better post this collected information into this blog, without any research paper structure and formalities.

I hope it would be useful to somebody.

The previous part with description of  idea you could find by this link.

Arduino air quality monitor for exhaust gasses measurement

Idea and issues

Main requirement for mobile monitoring devices is mobility, of course.
So, based on this idea, designed air quality monitor should have such features as:

1. autonomy with a help of battery,
2. autonomy in data output with a help of LCD.

Both these issues could be solved with help of old stuff that everybody has in a home (or in a buddy's home).

You can use any accumulators, the main problem is that single li-ion battery could give you only 3.7v, but for normal workflow you should have at least 5v.

The quickest way to solve this issue is just to connect sequentially 2 batteries. A problem of charging you can solve with help of controller from old laptop battery or with any other diy circuits for li-ion charging.

Siemens LPH8836 display + Arduino

Many years ago I had, maybe, the most useful phone in my life - Siemens m65. Luckily, LCDs from Siemens phones  are very convenient to connect. Also it is possible to use displays from cx65, and s65.

Inside the phone I have found the LPH8836-A display. In some other cases you could find LCD with another model. The difference between the ones is only in firmware features and circuit connection way, in fact, they are not significant.
The lph88 known as the most problematic Siemens display, but only problem I have found is that it need to be connected via all contacts.

Siemens lph88, ready to use

Layout of this display is very clear, the big area of contacts make able to solder wires easily.

Air quality monitor circuit

Total device circuit

The total circuit of my device includes:

• LCD LPH88
• sensor MQ-138
• sensor MQ-138;
• sensor MQ-131;
• sensor TGS-2201;
• sensor AM-2301;
• Arduino UNO r3 (DCCduino UNO);
• resistor 470 Ω — 5 units;
• resistor 820 Ω — 5 units;
• resistor 120 Ω — 5 units;
• diode 1N4148 — 1unit;
• diode Schottky — 1 unit;
• transistor — КТ972 — 1 unit;
• induction 680 μH — 1 unit.

Assembling

first test

Before using soldering iron I had tested circuit on a breadboard

second test

After test on the mobile phone, I have soldered wires to display and tested my assembling with simple Arduino program.

As long as in a result I have wanted to have the solid construction, I was obliged to create a circuit board. The quickest way to make it - just cut it out. Of course, the better way to produce circuit boards is chemistry, but if you do not need to have 0.5 mm ways on it, cutting is a possible variant.

After soldering of all components I had a solid module, matched witrh Arduino board.

After soldering of display wires I tested it - all works fine.

As a battery I have used 2 li-ion cells with controller from laptop battery.

Assembled device with flashed firmware.

Field testing and the wind problem

After assembling, I had tested this device indoor and everything works fine.
But the first outdoor test with cold air shows that direct hitting of wind flows on sensor heads make these sensors feel bad.
The solution of this problem was developed from 2 beer cans, with a help of which I had successfully formed a wind shield.

wind defence shield

When windflow hits the windshield it is influenced by Venturi effect. The speed of airflow inside the can would be slower than outside, and pressure - higher. Furthermore, holes split windflow to little flows inside a can.

Another positive effect - this solution would work even in winter, as long as this windshield is a good insulator.

 

Firmware

 

My Arduino ExhaustGasMeter project *.ino

You can use it in any way you want under MIT license.

Additional libraries which are needed for display connection you would find here:
https://github.com/watterott/Arduino-Libs

(updated)

IMPORTANT! 

Before fleshing, you need to edit a bit the S65LPH88.cpp library code.

For default pins this library uses

RESET: 17 pin (A3 for arduino)
SC: 16 pin (A2  for arduino).

In my case, the analogue pins are engaged by sensors. Thet's why for my circuit you need to change RESET pin number from 17 to 9; SC pin number from 16 to 8.

hungry electronics

Best regards, Andrii.