This board is similar to our Battery-board-DHT11 product but replaces the DHT11 sensor by a more accurate DHT22 dual temperature/humidity sensor, also made by AOSONG. This sensor can read positive and negative temperatures (from -40°C to 125°C) with 0.1°C precision and ±0.5°C accuracy. It also reads humidities in the whole 0-100% range with 0.1% precision and 2-5% accuracy. This sensor is fits well in lots of applications, including HVAC control and weather monitoring.
Figure 1 : panStamp Battery-board-DHT22 for wireless applications
In order to use Battery-board-DHT22, you only need to program a panStamp with our sample temphumpress application compiled with the TEMPHUM definition enabled from sensor.h. You will also need to enable DHT22 as the sensor to be used by the application:
By default, temphumpress takes Vcc as the actual battery voltage. However, all battery-boards have Analog 7 pin (panStamp 12th pin) directly connected to the battery. When using this application on a Battery-board, we advise enabling battery monitoring via the Analog 7 pin. From temphumpress.ino we have to uncomment the VOLT_SUPPLY_A7 definition:
Figure 2 : Base-board-DHT22 with panStamp and AA battery
Connection between panStamp and DHT22 sensor is the same as the one from the Battery-board-DHT11 page :
As you can see, the DHT22 is directly powered from the Arduino digital pin 15 (Analog 1). This lets the panStamp unpower the sensor whilst in sleep mode, reducing the current consumption to the maximum. For any other hardware reference please refer to our generic Battery-board product.
Firmware-side, when programmed with our sample temphumpress application, the board periodically sends temperature/humidity readings according to the value programmed in the TX_INTERVAL register, saved in EEPROM. This interval is 255 (0xFF) by default in "fresh"panStamps so you will need to program your desired interval after programming the module for the first time. After transmitting the reading, the panStamp enters the sleep mode, disconnecting most peripherals until the next transmission and hence drastically reducing the current consumption.