AM2302 Datasheet by Adafruit Industries LLC

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Your specialist in innovatinq humidity & temperature sensors
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Your specialist in innovating humidity & temperature sensors
Thomas Liu ( Sales Manager)
Email: thomasliu198518@ a liyun.com
- 1 -
Standard
Standard
Standard
Standard AM2302
AM2302
AM2302
AM2302 /DHT22
/DHT22
/DHT22
/DHT22 AM2302
AM2302
AM2302
AM2302 /DHT22
/DHT22
/DHT22
/DHT22 with
with
with
with big
big
big
big case
case
case
case and
and
and
and wires
wires
wires
wires
Digital
Digital
Digital
Digital relative
relative
relative
relative humidity
humidity
humidity
humidity &
&
&
& t
t
t
t emperature
emperature
emperature
emperature sensor
sensor
sensor
sensor AM2302
AM2302
AM2302
AM2302 /DHT22
/DHT22
/DHT22
/DHT22
1.
1.
1.
1. Feature
Feature
Feature
Feature &
&
&
& Application
Application
Application
Application :
:
:
:
*High precision
*Capacitive type
* Full range temperature compensated
* Relative humidity and temperature measurement
*C alibrated digital signal
*O utstanding long-term stability
*E xtra components not needed
*L ong transmission distance , up to 100 meters
*L ow power consumption
*4 pins packaged and fully interchangeable
2.
2.
2.
2. Description:
Description:
Description:
Description:
AM2302 output calibrated digital signal. It apply s exclusive digital-signal-collecting-technique and humidity
sensing technology, assuring its reliability and stability. Its sensing elements is connected with 8-bit single-chip
computer.
Every sensor of this model is temperature compensated and calibrated in accurate calibration chamber and the
calibration-coefficient is saved in type of programme in OTP memory, when the sensor is detecting, it will cite
coefficient from memory.
Small size & low consumption & long transmission distance( 10 0m) enable AM2302 to be suited in all kinds of
harsh application occasions. Single-row packaged with four pins, making the connection very convenient.
3.
3.
3.
3. Technical
Technical
Technical
Technical Specification:
Specification:
Specification:
Specification:
Model AM2302
Power supply 3.3- 5.5 V DC
Output signal digital signal via 1-wire bus
Sensing element Polymer humidity capacitor
Operating range humidity 0-100%RH ; temperature -40~ 8 0Celsius
Accuracy humidity
humidity
humidity
humidity +-2%RH
+-2%RH
+-2%RH
+-2%RH (Max +-5%RH) ; temperature +-0.5Celsius
Resolution or sensitivity humidity 0.1%RH ; temperature 0.1Celsius
Repeatability humidity +-1%RH ; temperature +-0.2Celsius
Humidity hysteresis +-0.3%RH
Long-term Stability +-0.5%RH/year
Interchangeability fully interchangeable
Your specialist in innovating humidity & remperarur-e sensars < 257="" -=""> ‘33 - 4| l A I .fl t at a 3: r1 ‘ u: -;u LLJ - _s.-, SEE 534”: ‘54:! U—4 V‘ as: n: r 1:1 {1'} =1 7:! C11 - xzsulmumrammmnui =1 ‘v 2:! Ln ll rm- v-wt‘ ‘ l ' , ‘ , I DATA-\rlhll X ‘ .. V.‘ ‘1 22%? a — I35 — — — 22 MCU 4m :37!» l-wire bus is used for communication between MCU and AM2302. ( Our l-wire bus is specially designed it's different fi'om Maxim/Dallas l-wire bus so it's incompatible with Dallas l-wire bus.)
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Your specialist in innovating humidity & temperature sensors
Thomas Liu ( Sales Manager)
Email: thomasliu198518@ a liyun.com
- 2 -
4.
4.
4.
4. Dimensions:
Dimensions:
Dimensions:
Dimensions: (unit----mm)
(unit----mm)
(unit----mm)
(unit----mm)
Standard
Standard
Standard
Standard AM2302
AM2302
AM2302
AM2302
s
s
s
s dimensions
dimensions
dimensions
dimensions as
as
as
as above
above
above
above
Big
Big
Big
Big case
case
case
case
s
s
s
s dimensions
dimensions
dimensions
dimensions as
as
as
as above
above
above
above
Red
Red
Red
Red wire--power
wire--power
wire--power
wire--power supply,
supply,
supply,
supply, Black
Black
Black
Black wire--GND
wire--GND
wire--GND
wire--GND
Yellow
Yellow
Yellow
Yellow wire--Data
wire--Data
wire--Data
wire--Data output
output
output
output
5.
5.
5.
5. Electrical
Electrical
Electrical
Electrical connection
connection
connection
connection diagram:
diagram:
diagram:
diagram:
6.
6.
6.
6. Operating
Operating
Operating
Operating specifications:
specifications:
specifications:
specifications:
(1)
(1)
(1)
(1) Power
Power
Power
Power and
and
and
and Pins
Pins
Pins
Pins
Power's voltage should be 3 .3 - 5.5 V DC . When power is supplied to sensor, don't send any instruction to the sensor
within one second to pass unstable status. One capacitor valued 100nF can be added between VDD and GND for
wave filtering.
(2)
(2)
(2)
(2) Communication
Communication
Communication
Communication and
and
and
and signal
signal
signal
signal
1-wire bus is used for communication between MCU and AM2302 . ( Our 1-wire bus is specially designed, it's
different from Maxim/Dallas 1-wire bus, so it's incompatible with Dallas 1-wire bus.)
Illustration
Illustration
Illustration
Illustration of
of
of
of our
our
our
our 1-wire
1-wire
1-wire
1-wire bus:
bus:
bus:
bus:
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Your specialist in innovating humidity & temperature sensors
Thomas Liu ( Sales Manager)
Email: thomasliu198518@ a liyun.com
- 3 -
DATA=
DATA=
DATA=
DATA= 16
16
16
16 bits
bits
bits
bits RH
RH
RH
RH data+
data+
data+
data+ 16
16
16
16 bits
bits
bits
bits Temperature
Temperature
Temperature
Temperature data+8
data+8
data+8
data+8 bit
bit
bit
bit s
s
s
s check-sum
check-sum
check-sum
check-sum
Example: MCU has received 40 bits data from AM2302 as
0000
0000
0000
0000 0010
0010
0010
0010 1000
1000
1000
1000 1100
1100
1100
1100 0000
0000
0000
0000 0001
0001
0001
0001 0101
0101
0101
0101
1111
1111
1111
1111
1110
1110
1110
1110 1110
1110
1110
1110
16 bits RH data 16 bits T data check sum
Here we convert 16 bits RH data from binary system to decimal system,
0000 0010 1000 1100 652
Binary system Decimal system
RH=652/10=65.2%RH
RH=652/10=65.2%RH
RH=652/10=65.2%RH
RH=652/10=65.2%RH
Here we convert 16 bits T data from binary system to decimal system,
0000 0001 0101
1111
351
Binary system Decimal system
T=351/10=35.1
T=351/10=35.1
T=351/10=35.1
T=351/10=35.1
When highest bit of temperature is 1, it means the temperature is below 0 degree Celsius.
Example: 1
1
1
1000 0000 0110 0101 , T= minus 10.1
16 bits T data
Sum= 0000 0010+1000 1100+0000 0001+0101
1111
= 1110 1110
Check-sum
Check-sum
Check-sum
Check-sum =the last 8 bits of Sum=1110 1110
When MCU send start signal, AM2302 change from standby-status to running -status . When MCU finishs sending
the start signal, AM2302 will send response signal of 40-bit data that reflect the relative humidity and temperature
to MCU. Without start signal from MCU, AM2302 will not give response signal to MCU. One start signal for one
response data from AM2302 that reflect the relative humidity and temperature. AM2302 will change to standby
status when data collecting finish ed if it don't receive start signal from MCU again.
See below figure for overall communication process , the
the
the
the interval
interval
interval
interval of
of
of
of whole
whole
whole
whole process
process
process
process must
must
must
must beyond
beyond
beyond
beyond 2
2
2
2 seconds.
seconds.
seconds.
seconds.
------------------------------------------------------------------------------------------------------------------------------------
1) Step 1: MCU send out start signal to AM2302 and AM2302 send response signal to MCU
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Your specialist in innovating humidity & temperature sensors
Thomas Liu ( Sales Manager)
Email: thomasliu198518@ a liyun.com
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Data-bus's free status is high voltage level. When communication between MCU and AM2302 begin s , MCU will
pull low data-bus and this process must beyond at least 1 ~10 ms to ensure AM2302 could detect MCU's signal, then
MCU will pulls up and wait 20-40us for AM2302's response.
When AM2302 detect the start signal, AM2302 will pull low the bus 80us as response signal, then AM2302 pulls
up 80us for pr eparation to send data. See below figure:
------------------------------------------------------------------------------------------------------------------------------------
2). Step 2 : AM2302 send data to MCU
When AM2302 is sending data to MCU, every bit's transmission begin with low-voltage-level that last 50us, the
following high-voltage-level signal's length decide the bit is "1" or "0". See below figures:
Attention:
Attention:
Attention:
Attention:
If signal from AM2302 is always high-voltage-level, it means AM2302 is not working properly, please check
the electrical connection status.
Your specialisr in innovafinq humidity & temperature sensors
Y
Y
Y
Your specialist in innovating humidity & temperature sensors
Thomas Liu ( Sales Manager)
Email: thomasliu198518@ a liyun.com
- 5 -
7.
7.
7.
7. Electrical
Electrical
Electrical
Electrical Characteristics:
Characteristics:
Characteristics:
Characteristics:
Item s Condition Min Typical Max Unit
Power supply DC 3.3 5 6 V
Current supply Measuring 1 1.5 mA
Stand-by 40 Null 50 uA
Collecting
period
Second 2 Second
8.
8.
8.
8. Attentions
Attentions
Attentions
Attentions of
of
of
of application:
application:
application:
application:
(1) Operating and storage conditions
We
don't recommend the applying RH-range beyond the range stated in this specification. The AM2302 sensor
can recover after working in ab normal operating condition to calibrated status, but will accelerate sensors' aging.
(2) Attentions to chemical materials
Vapor from chemical materials may interfere AM2302's sensitive-elements and debase AM2302's sensitivity.
(3) Disposal when (1) & (2) happens
Step one: Keep the AM2302 sensor at condition of Temperature 50~60Celsius, humidity <10%RH for 2 hours;
Step two: After step one, keep the AM2302 sensor at condition of Temperature 20~30Celsius, humidity
>70%RH for 5 hours.
(4) Attention to temperature's affection
Relative humidity strongly depend on temperature, that is why we use temperature compensation technology to
ensure accurate measurement of RH. But it's still be much better to keep the sensor at same temperature when
sensing.
AM2302 should be mounted at the place as far as possible from parts that may cause change to temperature.
(5) Attentions to light
Long time exposure to strong light and ultraviolet may debase AM2302's performance.
(6) Attentions to connection wires
The connection wires' quality will effect communication's quality and distance, high quality shielding-wire is
recommended.
(7) Other attentions
* Welding temperature should be bellow 260Celsius.
* Avoid using the sensor under dew condition.
* Don't use this product in safety or emergency stop devices or any other occasion that failure of AM2302 may
cause personal injury.

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