Blow sensor?

[Adam Aglionby]

Any suggestions for a sensitive thermistor or otherwise to act as a blow
sensor, dont really need a calibrated or accurate response, just detect the
presence or otherwise of a short pulse of moving air, like someone blowing
across something.

Hot wire anemometer seems a bit fragile and kinda struggling to find a
thermistor that dosen`t need a hurricane blowing across it to change.

Any Suggestions ?

Thanks
Adam

 

[John Popelish]

A Adam Aglionby wrote:

Any suggestions for a sensitive thermistor or otherwise to act as a blow
sensor, dont really need a calibrated or accurate response, just detect the
presence or otherwise of a short pulse of moving air, like someone blowing
across something.

Hot wire anemometer seems a bit fragile and kinda struggling to find a
thermistor that dosen`t need a hurricane blowing across it to change.

Any Suggestions ?

Thanks
Adam

Fairly small fairly low resistance value NTC thermistor in a bridge
should work.
Here are some part numbers for some small 1k thermistors available at
Digikey:
ERT-D2FGL102S (5mm disc)
KC003G (like small glass diode)
KC003N (2.79 mm dia, I think)

These need only a few milliwatts to raise their temperature a degree
C. Applying something like 5 volts across them should heat them well
above ambient and make them sensitive to air velocity. You can use a
second one operated at much lower current to compensate for air
temperature changes.


--
John Popelish

 

[dh]

Adam Aglionby wrote:

Any suggestions for a sensitive thermistor or otherwise to act as a blow
sensor, dont really need a calibrated or accurate response, just detect the
presence or otherwise of a short pulse of moving air, like someone blowing
across something.

Hot wire anemometer seems a bit fragile and kinda struggling to find a
thermistor that dosen`t need a hurricane blowing across it to change.

Any Suggestions ?

Thanks
Adam

I once used an elecret microphone as a simple blow detector in an
electronic flute project. Rectified the output through a capacitor and
sampled the voltage level with an A/D input of a microcontroller.
Sensitivity is affected a lot by the method you use to direct the
airflow into the microphone.