參數(shù)資料
型號(hào)： DS1821
廠商： DALLAS SEMICONDUCTOR
元件分類(lèi)： Switch/Digital Output Temperature Sensor
英文描述： DIGITAL TEMP SENSOR-SERIAL, 8BIT(s), 1Cel, ROUND, SURFACE MOUNT
封裝： PR-35, 3 PIN
文件頁(yè)數(shù)： 12/17頁(yè)
文件大小： 461K
代理商： DS1821
DS1821
Page 4 of 17
the 1-WIRE BUS SYSTEM section of this datasheet. These communications can include reading and
writing the high and low thermostat trip-point registers (TH and TL) and the configuration register, and
reading the temperature, counter, and slope accumulator registers. Also in this mode, the microprocessor
can initiate and stop temperature measurements as described in the OPERATION – MEASURING
TEMPERATURE section of this datasheet.
The TH and TL registers and certain bits (THF, TLF, T/R
, POL and 1SHOT) in the status/configuration
register are stored in nonvolatile EEPROM memory, so they will retain data when the device is powered
down. This allows these registers to be pre-programmed when the DS1821 is to be used as a standalone
thermostat.
Writes to these nonvolatile registers can take up to 10ms. To avoid data corruption, no
writes to nonvolatile memory should be initiated while a write to nonvolatile memory is in progress.
Nonvolatile write status can be monitored by reading the NVB bit in the status/configuration register:
NVB = 0 – a write to EEPROM memory is in progress, NVB = 0 – nonvolatile memory is idle.
THERMOSTAT MODE
In thermostat mode (T/R
= 1), the DS1821 can operate as a standalone thermostat that triggers according
to the TH and TL trip-points programmed while the device was in 1-wire mode. In thermostat mode the
DS1821 powers-up performing continuous temperature conversions, and the DQ pin acts as the
thermostat output.
Detailed operation of the thermostat output is provided in the OPERATION –
STANDALONE THERMOSTAT section of this datasheet.
Communications can be re-establish with the DS1821 while it is in thermostat mode by pulling VDD to 0V
while the DQ line is held high, and then toggling the DQ line low 16 times as shown in Figure 12. This
temporarily places the DS1821 in 1-wire mode, allowing microprocessor communication with the
DS1821 via the DQ pin. At this time any I/O function can be performed, such as reading/writing the TH,
TL or configuration registers or reading the temperature register. To return to thermostat mode, the same
procedure can be performed (pulling VDD to 0V while the DQ line is held high, and then clocking the DQ
line 16 times) or the power can be cycled. Note that temporarily putting the DS1821 into 1-wire mode
does not change the power-up mode of the device; this can only be changed by rewriting the T/R
bit in
the status/configuration register.
Also note that holding both VDD and DQ low for more than
approximately 10 seconds will cause the DS1821 to be powered down.
OPERATION – MEASURING TEMPERATURE
DS1821 output temperature data is calibrated in degrees centigrade and is stored in two’s complement
format in the 1-byte (8-bit) temperature register (see Figure 3), which the user can access when the
DS1821 is in 1-wire mode (T/R
= 0 in the status/configuration register). The sign bit (S) indicates if the
temperature is positive or negative; for positive numbers S = 0 and for negative numbers S = 1. Table 2
gives examples of digital output data and the corresponding temperature reading. For Fahrenheit
measurements, a lookup table or conversion routine must be used.
The DS1821 can be configured by the user to take continuous temperature measurements (continuous
conversion mode) or single measurements (one-shot mode). The desired configuration can be achieved
by setting the nonvolatile1SHOT bit in the status/configuration register: 1SHOT = 0 – continuous
conversion mode, 1SHOT = 1 – one-shot mode. Note that the 1SHOT setting only controls the operation
of the device in 1-wire mode; in thermostat mode, continuous temperature conversions are started
automatically at power-up.
In continuous conversion mode, the Start Convert T [EEh] command initiates continuous temperature
conversions, which can be stopped using the Stop Convert T [22h] command. In one-shot mode the Start
Convert T [EEh] command initiates a single temperature conversion after which the DS1821 returns to a
low-power standby state.
In this mode, the microprocessor can monitor the DONE bit in the
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
DS1821_07 制造商:DALLAS 制造商全稱(chēng):Dallas Semiconductor 功能描述:Programmable Digital Thermostat and Thermometer
DS1821+ 功能描述:板上安裝溫度傳感器 Programmable Digital Thermostat/Thrmmtr RoHS:否 制造商:Omron Electronics 輸出類(lèi)型:Digital 配置: 準(zhǔn)確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數(shù)字輸出 - 總線接口:2-Wire, I2C, SMBus 電源電壓-最大:5.5 V 電源電壓-最小:4.5 V 最大工作溫度:+ 50 C 最小工作溫度:0 C 關(guān)閉: 安裝風(fēng)格: 封裝 / 箱體: 設(shè)備功能:Temperature and Humidity Sensor
DS1821C+ 功能描述:恒溫器 Programmable Digital Thermo-stat/monitor RoHS:否 制造商:Maxim Integrated 功能: 開(kāi)路溫度: 閉合溫度: 準(zhǔn)確性:+/- 1 C 溫度范圍:- 55 C to + 125 C 電流額定值:500 uA 電壓額定值:2.7 V to 5.5 V 產(chǎn)品:Thermostats
DS1821-C02 功能描述:板上安裝溫度傳感器 RoHS:否 制造商:Omron Electronics 輸出類(lèi)型:Digital 配置: 準(zhǔn)確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數(shù)字輸出 - 總線接口:2-Wire, I2C, SMBus 電源電壓-最大:5.5 V 電源電壓-最小:4.5 V 最大工作溫度:+ 50 C 最小工作溫度:0 C 關(guān)閉: 安裝風(fēng)格: 封裝 / 箱體: 設(shè)備功能:Temperature and Humidity Sensor
DS1821-C04 制造商:DSC 功能描述:
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