aosong DHT12 User manual

Digital temperature
Product
Product
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超
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Stan
For more information,

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A product overview
DHT12 Digital temperature and humidity sensor is a
calibrated digital output record of temperature and humidity,
DHT11 The upgrade product. Application-specific digital
temperature and humidity sensor module and semiconductor,
ensure high reliability and excellent long-term stability.
DHT12 With a single bus, and standards I2C Two kinds of
communication and single bus communication mode is fully
compatible with DHT11。Standard bus interface makes it simple
and quick to system integration. With super small size, low power consumption, suitable for a wide
variety of applications.I2C Communication uses standard communication sequence, the user can
directly I2C Communication on the bus, no additional wiring, simple to use. Two way switch, users
are free to choose, easy to use, should be a broad range of areas. Products for the 4 Lead,
convenient connection, provides special packages according to user needs.
Second, the scope of application
Heating, ventilation and air conditioning , Dehumidifier, test and inspection equipment,
consumer products, automotive, automation, data recorders, weather stations, home
appliances, control, Medical and other relative humidity control.
Third, product highlights
Fully interchangeable, low cost, long term stability, relative humidity and temperature
measurement, signal transmission of long distance, digital output, precise calibration, power
consumption is very low, the standard single-wire digital interface, the standard I2C Bus digital
interface, communication can be freely chosen.

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Four, dimensions (unit:mm）
图1DHT12 Profile of best-inch
External interface:1:VDD 2:SDA 3: GND 4:SCL
Five, sensor performance
5.1 Relative humidity 5.2 Temperature
表1：DHT12 Relative humidity tables 表2：DHT12 Relative performance table
Paramete
rs
Condit
ions
mi
n
ty
p
m
ax
W
ork
uni
t
Paramete
rs
Condit
ions
mi
n
ty
p
m
ax
Wo
rk
uni
t
Resolution
0.1
%R
H
Resolution
0.1
℃
Measuring
range
20
95
%R
H
16
bit
Precision 1
60%RH
±
5
%R
H
Precision
25 ℃
±
0.5
℃
1
此精度为出厂时检验时，传感器在 25℃和 5V，条件下测试的精度指标，且只适合非冷凝环境。
参数
条件
min
typ
max
单位

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Repeatabilit
y
±
0.3
%R
H
Measuring
range
-
20
60
℃
Interchange
ability
Fully interchangeable
Repeatabilit
y
±
0.2
℃
Response
time 1
1/e(63%)
<2
0
S
Interchange
ability
Fully interchangeable
Hysteresis
±
0.5
%R
H
Response
time
1/e(63%)
<
20
S
Drift 23
Typical
value
<0
.5
%RH
/yr
Drift
±
0.1
℃/y
r
供电电压
2.7
5
5.5
V
功耗 4
休眠
30
µA
测量
800
µA
平均
150
µA
低电平输出电压
IOL5
0
300
mV
高电平输出电压
Rp<25 kΩ
90%
100%
VDD
低电平输入电压
下降
0
30%
VDD
高电平输入电压
上升
70%
100%
VDD
Rpu6
VDD = 5V
VIN = VSS
1
4.7
10
kΩ
输出电流
开
8
mA
三态（关
）
10
20
µA
采样周期
2
S
1
在25℃和 1m/s 气流的条件下，达到一阶响应 63%所需要的时间。
2
在挥发性有机混合物中数值可能会高一些。见说明书应用储存信息。
3
此数值为 VDD =5.0V 在温度为 25℃时，2S/ 次，条件下的平均值。

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图2：25 ℃时 DHT12 Relative humidity maximum error 图3: Temperature sensor temperature Max
errorsSix, electrical characteristics
Electrical characteristics, such as energy consumption, high and low level input and output
voltage, depending on the power supply. Table 3 Details DHT12 The electrical characteristics,
without marking, it means that the power supply voltage is
12
V。
表3：DHT12 DC characteristics.
Seven, interface definition
7.1 DHT12 Pin assignments
表4 ：DHT12 Pin assignments
图4：DHT12Wiring diagram
7.2Power supply pins (VDD GND）
DHT12 The supply voltage range 2.7V - 5.5V。
7.3 Serial clock input (SCL）
SCL Pins are used for selection of the means of communication and I2C Communication
clock line. Dang SCL After power remained low, indicating that the user select a single bus
1
低电平输出电流。
2
表示上接电阻。
PIN
The
name
描述
1
VDD
Power supply (2.7V-5.5V)
2
SDA
Serial data, bi-directional
3
GND
地
4
SCL
Serial clock input(Single bus grounding)

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system communication, otherwise I2C Communication after the selected communication
mode, in power during the sensor communication remains the same if you want to change,
as a way, please power on again, and select communication according to operational
requirements. When you select I2C Communication,SCL For the microprocessor DHT12
Communication between the synchronization.
7.4 Serial data (SDA）
SDA PIN for a three-State structure, used for reading and writing data. Specific
communication timing, see the detailed description of the communications.
EightI2C And single-bus communication protocol
DHT12 Serial interface, read sensor signals and power loss, do the optimization. Sensors
with a single bus,
I2C Two way output, communication mode switch, easy to use. Bus to SCL Signal cable power
levels to determine their bus communication mode: when power on SCL Remained low for a
single bus communication mode when power on SCL To maintain a high level I2C
Communication mode. Single main line single bus communication is fully compatible with the
company's other products;I2C Communication in accordance with I2C Standard protocol
address can be directly linked to I2C On the bus (bus allowed only one product), no additional
wiring, operation is very simple. Read DHT12 The sensor, please in strict accordance with the
two types of communication protocols and timing. Specific details see single bus
communication protocol and I2C Communication protocol details.
8.1DHT12 Sensor I2C Communication protocol
DHT12 Support I2C Way to communicate, in full accordance with I2C Standard protocol
prepared, can be linked directly in I2C Bus sensor SDA PIN I2C Data bus,SCL 接I2C Clock bus,
customers need to both pin a 1KΩ~10KΩPull-up resistor.I2C Address for 0xB8(DEV SEL); I2C
Communication rate cannot be higher than 400KHZ。
BYTE ADDR
R/W
Desc.
Note
0x00
R
Humidity integral
digits
Relative humidity
values
0x01
R
Humidity scale

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0x02
R
Temperature
integer bit
The temperature
value
0x03
R
Temperature
scale
0x04
R
Checksum
Data refer to the single bus data processing sample.
◎I2C Interface attributes
Must be in strict accordance with the following distribution specification, otherwise the
sensor does not work.
Communication protocol:
图13 I2C Communication
protocolReading time:

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图14 I2C Reading sequence
diagramsReference sequence:
图15 Reference sequence diagramNote: the actual test data
refer to the single bus-processing example.
8.3Single bus communication (ONE-WIRE）
◎Single bus description
DHT12 A simplified single-bus communication. That only a single bus cable, system of data
exchange,Control is done by a single bus communication. Devices (hosts) through a drain or a
three-State port is connected to the data cable to allow device does not send data will be released
when the bus, while letting the other device uses the bus; usually require add-ins a single bus
around 4.7KΩPull-up resistor, so that when the bus is idle by default high State. Because they are
the master-slave relationship, only when the host calls the sensor, the sensor responds, so host
access must be strictly followed during single bus timing, timing disorder if will not be able to
correctly read data of temperature and humidity.
◎Single bus transfer data definitions
SDA PIN for client hosts DHT12 Communication and synchronization between, by-wire data
format, a transfer 40 Data high first. Specific communicationSequential as shown in the following
figure, communication formats described in the following table.
图16 Single bus communication timing description
◎Single bus data example:
The name
Single bus format definition
The starting
signal
Host data bus (SDA) Down over time (18ms), Tells sensors to prepare data

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The
corresponding
signal
Sensor data bus (SDA), Lower 80µsAnd higher 80µs In response to host the
starting signal
Data format
Receives a host after the starting signal, sensors at once from the data bus
(SDA) 40 Data, high
Humidity
Humidity high humidity integer data, humidity low humidity decimal data
Temperature
Temperature high temperature integer data, temperature low temperature
decimal data, and low temperature Bit8 为1 The negative temperature,
otherwise positive temperature
Check digit
Check digit=Humidity high+Humidity is low+Temperature highs+Low
temperature
Example: receiving 40 Data for:
00111000 00001000 00011010 00000110 01100000
Humidity integral digits Humidity scale Temperature integer
bit Temperature scale Check digit
00111000+00001000+00011010+00000110=01100000(Check digit)
receive data properly:
Humidity:00111000 (Binary) =>56 (Decimal)00001000(Binary)=>8 (Decimal)
=>Humidity=56.8%RH
Temperature:00011010 (Binary) =>26 (Decimal)00000110(Binary)=>6 (Decimal)
=>Temperature= 26.6 degrees
Celsius Example two: received 40 Data for:
00111000 00001000 00011010 10000110 11100000
Humidity integral digits Humidity scale Temperature integer
bit Temperature scale Check digit
00111000+00001000+00011010+10000110=11100000(Check digit)
receive data properly:
Humidity:00111000 (Binary) =>56 (Decimal)00001000(Binary)=>8 (Decimal)
=>Humidity=56.8%RH
Temperature: temperature low 8Bit 为1 It indicates sampling the temperature to
minus-temperature
00011010 (Binary) =>26 (Decimal)
10000110 (Binary,Ignore 8Bit)=>6(Decimal)

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=>Temperature=-26.6 degrees Celsius
◎Peripheral reading steps
Communication between the host and the sensor reads data by completing the following
three steps.
Step one:
DHT12 After power up (start wait 2 Seconds to cross the unstable condition of the
sensor)Tested environment temperature and humidity data, and record data, sensor automatic
hibernation.DHT12 The data because of the pull-up resistor has remained high, at this time DHT12
的SDA PIN is input, detect external signals.
Step two:
Hosting by SDA Data bus output low level and low level for at least 200ms Released by
bus,DHT12 Detects a bus free, issue 80µs Low level immediately 80µs High level signal, as shown
below:
图17 Signal
diagramStep three:
DHT12 After the response is sent immediately by the continuous serial data bus output 40
Data host under the bus level receive 40 Bit data.
Bit data"0"Format:50µs Low level plus 26-28µs High level; data"1"Format:50µs
Low level plus 70µs High level; data"0", Bit data"1"Signal format shown in the
following figure:
图18 Bit data"1"和"0"Format signal