11. Input devices¶
Group assignments¶
- Measure the analog levels and digital signals in an input device
Measure an input device.¶
Datasheet of DHT11¶
DHT11 is a available humidity and temperature sensor.
Open the case¶
Open the sensor’s case and take a look inside.
Two sides of DHT11 sensor, there is a ATtiny45-like chip installed.
When the resistance value of component at the middle of board is measured,
resistance is always over-range.
That shows it probably is a humidity sensitive capacitor.
Measure it¶
It is a pre-fab commertial device for air quality,
which ( looks likely ) use the same componant of DHT11.
When a finger touch to surface of sensor, signal and data on the monitor changed.
Compare results with datasheet¶
Datasheet of DHT11 show it communicate by serial signal,
but the device seems to do it by voltage or current.
Probably It was modified to lower cost and price.