DIY Airflow Sensor

Low Cost, Analogue Airflow Sensor

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. (CC BY-NC 4.0)

If you want to help improve this design or have a comment or any questions, please reach out via the comments or a private message.

Goals:

1. Affordable
2. Easy to work with
3. Easy to assamble
4. 5V Arduino compatible

Theoretical thoughts:

NTC Resistors are heated up through the current that is flowing through. Two NTC Resistors are used in the wheatstone bridge to enhance the affect. When the NTC Resistors heat up their resistence drops and the voltage between C and D gets bigger. This voltage difference can be measured (and amplified with an instrumentional amplifier). When airflow is present the resistance rises again and the voltage difference goes back to zero.

3x 1kΩ

3x 10kΩ

1x INA333AIDGKR

1x pin header 1x3

2x 1k NTC

1x PCB

As discussed in the theoretical thoughts a wheatstone brigde is used to measure the signal. An INA333 instrumentational amplifier with a gain of 5 and a voltage reference of 2.5 V is used to get a suitable ananlog signal which can be measured with an arduino or other microcontroller.

The layout of the PCB is pretty simple. The two NTC Resistor can be solderd in the front, with small wires so as low as possible amount of heat is wasted.

The PCB can be manufactured through the usual channels. On the back of the PCB is a 8x8 mm rectangle for a QR code or data matrix

I can provide the Gerber files on request.

The components can be easily soldered onto the board according to the schematics. Two NTC 1k Resistors are soldered in the front. They heat up through the current flowing through them, and are cooled by the airflow around them.

A voltage on the Analog pin of around 4 is reached through the self heating of the NTC resistors. When they are cooled the voltage drops to 2.5 V which is the reference voltage set on the operational amplifier. This reference voltage could be lowered to give a higher measureing range with a higher gain set on the operating amplifier. Good results that don’t have too much noise is achieved with a condesator close to the module and a pulldown resistor on the analog line.

I hope you find this instructable helpful. If you have any questions feel free to reach out!

Have a nice day :)