DIY Touch Screen Trimix Analyser

[Francisco Trevisan PY2ALC]

Bill of material

WEMOS LOLIN or compatible ESP32 board
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3.2 inch 320*240 SPI Serial TFT LCD Module Display Screen with Touch Panel Driver IC ILI9341 for MCU

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DC-DC Step Down Converter Module LM2596 DC 4.0~40 to 1.3-37V Adjustable Voltage Regulator


Adjust it to 3V output!

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16 Bit I2C ADS1115 ADS1015 Module ADC 4 Channel with Pro Gain Amplifier 2.0V to 5.5V for Arduino RPi
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XH 2.54mm connectors and terminals 2 and 4 pins
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XH 2.54 cables 2 and 4 pins
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MD61 Thermal Conductivity Gas Sensor
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CITY AO2 PTB-18.10 A02 AA428-210 or similar Oxygen Sensor
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18650 Li Ion battery
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18650 Li Ion battery case (serial connected)
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10k 1206 SMD resistor
2k 1206 SMD resistor
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500 ohms multi turn trimmer potentiometer (Y pattern)
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Custom main PCB
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Custom sensor PCB
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Switch
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Molex or an appropriate connector and terminals for the O2 cell. For more info see the sensor’s datasheet.
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Links to resources are for your reference only. I do not have any connection to the owners of the shops I listed. You can find most of these components easily on aliexpress, ebay, bangood…. etc.

pls post here for us the arduino code...and the pcb to make at pcbway.com gerber file pls

 

[Jarek Andrzejewski]

My experience with combining the oxygen sensor (0-50mV) with the carbon monoxide sensor (0.4-2V) is that they influence each other too much for an independent reliable measurement. But I'd be curious to know how to solve that issue!

Maybe resistor divider on CO input (bringing down original 0.4-2V to ~10-50mV at ADS input) would help?

 

[kaiserb]

Likely if you are reading against GND you have multiple GNDs affecting the accuracy of the ADC between the 2 input signals. Either tying all your GNDs together or totally separating the power for one of the sensors can solve your issue.

I have a proto built using an ADS 1115, to do differential readings between A1/A2 and a diff between A3/A4. I have had no issues with dual readings but I was using 2 O2 sensors with similar mV ranges.