Page WILL BE tested for compliance with INDUSTRY (not MS-only) standards, using the free, publicly accessible validator at validator.w3.orgBefore we get too excited about the "obvious" candidates, a word about the DS2438 Smart Battery Monitor. Don't forget that has a temperature sensor built into it. If your system already has one of those, you may not need a DS18xx as well! Do note, however, that as the DS2438 is a SMT device, it may be unduly affected by heating of your PCB by the operation of the circuits on it.
This material needs polishing, but may be useful already...
Found from...
http://www.maxim-ic.com/quick_view2.cfm?go=part_number_search
DS1822:
The DS1822 is a digital thermometer with +/-2°C accuracy over a -10°C to +85°C range. Data is read out over a 1-Wire® serial bus in 2's complement format with 9 to 12 bits of resolution (user-programmable).
The DS1822 offers thermostatic functionality with over-temperature (TH) and under-temperature (TL) user-programmable setpoints stored in on-chip EEPROM. An internal flag is set when the measured temperature is greater than TH or less than TL. If thermostatic operation is not required, the two bytes of EEPROM reserved for TH and TL may be used for general-purpose nonvolatile storage.
DS18S20 (aka DS1820S?)- Recommended replacement for DS1820:
The DS18S20 Digital thermometer provides 9-bit centigrade temperature measurements and has an alarm function with nonvolatile user-programmable upper and lower trigger points. The DS18S20 communicates over a 1-Wire® bus that by definition requires only one data line (and ground) for communication with a central microprocessor. It has an operating temperature range of -55°C to +125°C and is accurate to +/-0.5°C over the range of -10°C to +85°C. In addition, the DS18S20 can derive power directly from the data line ("parasite power"), eliminating the need for an external power supply.
DS18B20: Datasheet easy to miss on Dallas site.
The DS18B20 Digital Thermometer provides 9 to 12bit centigrade temperature measurements and has an alarm function with nonvolatile user-programmable upper and lower trigger points. The DS18B20 communicates over a 1-Wire bus that by definition requires only one data line (and ground) for communication with a central microprocessor. It has an operating temperature range of 55°C to +125°C and is accurate to +/-0.5°C over the range of 10°C to +85°C. In addition, the DS18B20 can derive power directly from the data line ("parasite power"), eliminating the need for an external power supply.
=== end from site...
BUT! Closer reading of at least one of these device's sheets in the past speaks of reading tture to more precision... not "accurate" that far? Bah! And old datasheets (DS1820) not immediately, if at all, accessible at site. Bah!
DS18S20 has RESOLUTION of up to 0.0625 °C... but ACCURACY of only 0.5°C., over range -10 -+85°C. Op range: -55-125°C.
DS1822: Same, EXCEPT accuracy only 2° (But has extra feature already mentioned.) In DS1822 datasheet: "Also available is the high-precision DS18B20, which provides +/-0.5°C accuracy and is software-compatible with the DS1822."... so... did the DS18B20 also offer the flags?
18B20: There was a bad batch... and poor customer support.
Note: DS1822 has internal flags for "there HAS BEEN an under/ over tture event since you last visited". Others can alarm WHILE under/ over exists.
Search site for DS1820, and you get three hits: DS1820, DS1820B, DS1820S. Click on link for DS1820B, and you get page for DS1820. Search on DS18B20, and you get different results.
Bottom line:
DS1820 seems to be obsolete.
DS1822 has flags, but I don't want them, but lower accuracy.
DS18S20 seems to be the chip for me....
Do you have an "always on" internet connection, e.g. DSL or broadband? (Even a basic home user account is fine. You don't need a fixed IP address.) Want to set something up that lets you check all is well at your home or business.... from any internet terminal in the world? (The terminal needs nothing more than a standard browser.) You don't have to spend anything on software, everything you need is free. You might want to dedicate an old Win98 "box" to doing the work, but you don't have to. You'll probably want to spend a little money to attach one or more 1-Wire temperature sensors to the system, but there are ways around even that expense.
Sound interesting? See the pages about my FarWatch system.
Page WILL BE tested for compliance with INDUSTRY (not MS-only) standards, using the free, publicly accessible validator at validator.w3.org
....... P a g e . . . E n d s .....