Are there any low-cost (<50$USD) wireless ambient temperature sensors available?
I would like a simple to interface to the sensor i.e. IP over Wifi if at all possible.
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\$\begingroup\$ Unfortunately a WiFi adapter itself is going to run you at least $50. Also WiFi is not a good choice for temperature sensors, due to its high complexity and power requirements. You want something that is very low power, so that you can run your sensor for months off a single battery. \$\endgroup\$– davrCommented Mar 15, 2010 at 16:16
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\$\begingroup\$ There are wifi temp/humidity sensors that rated for 2 years of battery life with 0.1%-0.5% duty cycle \$\endgroup\$– ZepplockCommented Jul 31, 2011 at 15:47
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7 Answers
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Not wifi but a standalone XBee + temperature sensor will do this for around $30-$40 or so. The XBee has a uC + A/D converter and could read an analog sensor. At a 0.1% duty cycle (transmitting for 1 second every 1000 seconds) you can get around two years on two AA's with a fairly simple design.
I have a short ZigBee writeup at http://wiblocks.luciani.org/white-papers/intro-to-zigbee.html
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\$\begingroup\$ Non-pro XBees are rated at ~1mW at their lowest power setting, which will give you near 100% packet transmission within ~10 feet (line of sight) in my experience, an XBee Pro has a max power consumption of ~300mA during transmission but is rated for 1+ mile line of sight. The non pros can do something like 100ft with their max power consumption (about 1/10 of the pro I believe). \$\endgroup\$– pfyonCommented Mar 16, 2010 at 21:57
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\$\begingroup\$ The numbers that I listed in the writeup are from the XBee literature sited at the bottom of the page. For a whip antenna they state a performance increase of 5:1 (pro:std). For the chip antenna the range is around 3.5:1. These values are all outdoors, line-of-sight. Indoors the difference is only around 2:1 and the ranges are 140ft:80ft. \$\endgroup\$– jlucianiCommented Mar 17, 2010 at 12:25
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\$\begingroup\$ I just added an application hint for using the PICOBEE to measure K-type thermocouples and transmit the timestamped data using the XBEE. The schematic, prototype pics and software example is at wiblocks.luciani.org/docs/app-notes/picobee-tc.html \$\endgroup\$– jlucianiCommented Jun 11, 2011 at 16:06
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\$\begingroup\$ IoT has changed since 2010. In 2018 it is possible to make this with Espressif ESP32 or a Particle Photon board. \$\endgroup\$– Jeroen3Commented Jul 4, 2018 at 12:09
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One solution would be to use a a JeeNode and a JeeLink (plugged into a PC or router). Cheap, open-source and programmable from the Arduino IDE.
answered Mar 15, 2010 at 18:26
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\$\begingroup\$ Looks like a proprietary protocol... is it? \$\endgroup\$– jldupontCommented Mar 16, 2010 at 2:01
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\$\begingroup\$ The RFM12B module does FSK on a configurable frequency, yes. But the JeeNode comms protocol is open source. \$\endgroup\$ Commented Mar 16, 2010 at 6:58
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Another vote for a JeeNode radio and receiver. I suggest you review this weather station wireless implementation:
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The book 'Practical Arduino', available from little bird electronics (and elsewhere) contains information on how to decode the data from wireless temperature probes as sold with consumer weather stations.
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\$\begingroup\$ In Australia, I've seen wireless indoor outdoor thermometers in supermarkets for around $9. I've looked at the data stream, and they seem reasonably hackable. $9 per node with a lot of spare receiver circuits left over seems reasonable. \$\endgroup\$ Commented Nov 17, 2013 at 8:37
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You might want to consider building such a device yourself. If you need the communication to be over TCP/IP networks then the mbed has in-built ethernet capabilities and could communicate temperature data (and a lot more!), but you would need to buy a wifi adaptor for wireless comms. As davr points out, thats going to be a power drain at the least!
Alternatively you could use an arduino and a zigbee module to send the data over potentially large distances back to a controller device with the lower power 802.15.4 protocol.
Either way I think you're going to have to get your hands dirty and build the thing yourself. The bonus of that approach is that depending on how far to need to communicate wirelessly over, you could keep the cost down.
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\$\begingroup\$ Maybe it's just me, but mbed seems overpriced. The board is $100, but the actual microcontroller can be bought for $10. I didn't look at it much, maybe their software is really good & that makes up for the cost? \$\endgroup\$– davrCommented Mar 15, 2010 at 20:48
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\$\begingroup\$ Its $100?! Wow, I bought mine for £30 over here—which is easily comparable with the cost of a programmer and a chip or two. Yeah, $100 is a bit steep! \$\endgroup\$– JP.Commented Mar 16, 2010 at 10:26
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\$\begingroup\$ I never seen it sold for $100. $60 rather. It has a USB programmer, Flash memory and an Ethernet PHY on board. Not to mention you don't have to solder a TQFP100. \$\endgroup\$– jpcCommented Apr 28, 2010 at 15:43
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Why not use a standard remote sensor for a consumer-grade weather station? Most of the ones you find in stores are made by Oregon Scientific. I'm not sure of the wireless band and the protocol, but it ought to be fairly simple and probably documented somewhere out there on the internet.
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1\$\begingroup\$ +1 for the useful link. I am looking for something with an API i.e. I want to interface the sensor to a computer. \$\endgroup\$– jldupontCommented Mar 17, 2010 at 10:52
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DISCLAIMER I do work for that Yoctopuce company which designed the product described here, so that answer might not feel as altruist as you would like it to be.
You might want to have a look at Yocto-Temperature and YoctoHub-Wireless from Yoctopuce. The Yocto-temperature is a just regular USB temperature sensor as you can find many on the internet, but it can be plugged on a YoctoHub-Wireless from the same company. That hub is a WiFi transmitter which can control any Yoctopuce device. You will then have direct WiFi access to your sensor. You can also ask the hub to automatically report sensors data on a server of your choice (much easier to go through NAT filters that way).
Ease of use
Plug, configure, program your application and play. But you will have to work on the enclosures, especially if you want to put it outdoors as I suspect.
Electrical consumption
WiFi is a power greedy technology. Actually a YoctoHub-wireless + one sensor consumption is about 140mA. But the hub features a deep sleep mode. In that mode the hub wakes up from time to time, post sensors data, and goes back to sleep. Consumption in deep sleep more is less than 15 uA. Then, depending on how you configure it, the installation can hold on batteries for weeks... or months.
Price
More than $50, I'm afraid. But I seriously doubt you can find a reliable WiFi temperature sensor for less than $50. Note that if you use a cheaper technology, you will have to buy a bridge between that technology and your network. Moreover, if you really think that more than $50 is a deal breaker, you should ask yourself how much you would like to be paid to provide what you're asking for. And don't forget: that money is supposed to pay for raw components and to feed you as well :-)
Application
Here is a application example involving a YoctoHub-Wireless and an Yocto-Meteo which is just an improved Yocto-Temperature. Basically it's an outdoor solar-powered, wifi, temperature/humidity/atmospheric pressure sensors array. It is powered by one of these USB solar chargers. http://www.yoctopuce.com/EN/article/an-autonomous-solar-weather-station
Alternatives
Here are some other WiFi alternatives, which I believe are as good as the Yoctopuce one, minus the power issue handling.
DIY Hardcore: Arduino + wifi shield + temperature sensor such as http://www.sparkfun.com/categories/82
DIY casual: Raspberry PI + USB wifi dongle + usb temperature sensor . Note that USB temperature sensors are very common: http://www.phidgets.com/products.php?category=35 http://www.raphnet.net/electronique/usbtenki/index_en.php
Ready to use: Temper@tureAlert have a whole range of ready to use temperature sensors, including wifi version http://www.temperaturealert.com/Temperature-Alarm.aspx
As a conclusion
The hardware is just the visible part of the iceberg. Whatever solution you choose, make sure you choose one with a decent API, or it will be useless.
