Igor, Just to follow up on this... I was at Sam's Club yesterday (a US based membership store that is part of Walmart). I just happened to run into a weather station type device they are selling made by Sharp that has a remote temperature and humidity sensor that links to the base unit via radio. The remote sensor is about the size of a TV remote control. The box said it will communicate with the base unit 300+ feet away. Everything runs off batteries. That unit was $29.00.
They had another unit of a different manufacturer that also had a remote temperature sensor but the distance was limited to about 100 feet. Anyway, neither of these devices connect via ethernet, but perhaps they do what you need in case the low tech John Deere dial thermometer breaks the budget. ;-) There was also some alarm function on the Sharp unit. You may be able to set a temperature triggered alarm. Monitoring coop humidity might be nice also. Dave On 7/25/2011 5:34 PM, dave wrote: > The AD592 ( analog.com ) should be relatively noise free over reasonable > distances. 1.0 uA/degree K. Bias it with something between 4 and 20 V > and use a current to voltage converter near the computer. The time > constant is pretty good if in flowing air and even better with a small > Al heat sink. > > HTH > > Dave > > > > > > On Sat, 2011-07-23 at 11:53 -0400, gene heskett wrote: > >> On Saturday, July 23, 2011 11:33:03 AM Przemek Klosowski did opine: >> >> >>> On Fri, Jul 22, 2011 at 3:15 PM, Igor Chudov<[email protected]> wrote: >>> >>>> El cheapo ethernet routers cost $9.99: >>>> >>>> http://www.newegg.com/Product/Product.aspx?Item=N82E16833166034 >>>> >>>> I believe that a cheap Ethernet thermometer would cost roughly as >>>> much, if someone wanted to produce it. >>>> >>> Yeah but this Rosewill box is really a plastic box with five >>> connectors surrounding a dedicated ethernet switch chip---a mass >>> market item that's cheap because they make zillions. Anything else has >>> volumes that are multiple orders of magnitude smaller. >>> >>> To get a good price, the only way is to judo the strength of the mass >>> market---repurpose an OpenWRT router or a cast-off PC. Even then, >>> however, you need the Ethernet cable AND the power line---unless you >>> jigged the power (low-voltage DC, of course) over the unused pairs in >>> the Ethernet. >>> >>> This gives me an idea--I think it might work to hook one of those >>> two-wire or I2C Dallas/Maxim temp sensors over a long 'ethernet' >>> cable, and bitbang them. Does anyone know what are the practical >>> limitations on I2C/two-wire? A twisted-pair ethernet cable should >>> help... >>> >> >> Unforch, I2C is not really suited for long distances, the cables >> capacitance limit is 400 pf, it is not a "terminated" transmission line >> design by any stretch. No cat5 type cable has any advantage in its twisted >> pair, differential receiver design. Neither do the std 4 wire phone >> cables. 40 feet and I2C is Dead in the Water. >> >> That isn't saying that a 3 wire circuit, with active pullups that also >> serve as terminators for echo& ringing control, couldn't be made to work >> at 100's of yards, but the thing is going to need about 5 watts of power >> available at both ends of the cable for driver and term power. If flat >> ribbon cable was used, which has an impedance of about 110 ohms, then the >> chips designed for active terms on a scsi bus could be 'borrowed', but for >> other cable types, like 4 wire round or flat telco and cat5 twisted pair >> styles, the term match will not be as close as they will range down to the >> 60 ohms area. One might be reduced to looking at first one end, then the >> other of the circuit and adjusting the terminating R for minimum ringing >> and echo's as seen on a 100 mhz scope. Not practical for a just plug it in >> and its supposed to work, even for folks who have no clue what 'VSWR' >> stands for. >> >> The lesson is to stick with properly terminated twisted pair cabling if any >> distance is involved. >> >> Cheers, gene >> > > ------------------------------------------------------------------------------ > Storage Efficiency Calculator > This modeling tool is based on patent-pending intellectual property that > has been used successfully in hundreds of IBM storage optimization engage- > ments, worldwide. Store less, Store more with what you own, Move data to > the right place. Try It Now! http://www.accelacomm.com/jaw/sfnl/114/51427378/ > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > > ------------------------------------------------------------------------------ Storage Efficiency Calculator This modeling tool is based on patent-pending intellectual property that has been used successfully in hundreds of IBM storage optimization engage- ments, worldwide. Store less, Store more with what you own, Move data to the right place. Try It Now! http://www.accelacomm.com/jaw/sfnl/114/51427378/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
