Picture of TempBug: internet-connected thermometer
Last January, we had some trouble with the heat in my office. Specifically, the kind of trouble wherein the heat is not on, you turn it up, and it still not on. This went on for more than a few days, and finally ended a day or two after we got an email announcing that the heat was broken and speculating that it had probably been down for a few days. My teammates and I laughed a bit at this - we knew exactly when the heat had stopped working. We had a continuous record of the temperature in the office going back months, with 10-minute resolution.

You can do this too, and it's quick, cheap, and easy! This little gadget is built around an electric imp, and you can push the data from the imp out to anywhere you want. In my case, I found it handy to push the data to a neat service called Xively, which stores and graphs the data for free.

This project takes about an hour to two hours, if you've never done a project with an electric imp before, and when you're done you'll have a thermometer that you can toss anywhere with wifi and collect data for months to years on a single battery, depending on how often you check the temperature.
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BenC411 days ago

What kind of wireless range does the imp have?

KRS Test29 days ago

Thanks for a great list of instructions. You really have done an outstanding job making this manageable for a for someone with limited tech skills!

I have been able to setup the code and the integration to Xively but am having trouble with the readings. The readings remain steady at say 50 for quite a while then spike up to 120 or plunge to -119. Sometimes they stay at say -10 for an extended period of time. Attached is a picture of the Xively graph.

Have tested the readings by placing the E-Imp next to hot and cold items but there is little fluctuation in the readings.

No doubt I have made a simple error somewhere but am struggling to find it.

For the moment the power supply is by USB from a laptop. Am planning on soldering on the battery once the readings work properly.

Any feedback or suggestions would be appreciated.

Thanks again!

Electric Imp output.jpg
lenny20204 months ago

I tried to build it--great, thorough, easily understandable instructions, but I am not getting any info posted to Xively. I copied the info for lines 7 and 8, and although the project seems to cycle as expected, the log states:

Posted to Xively: 120.21, got return code: 56, msg: <html>

<head><title>400 Bad Request</title></head>

body bg color="white">

<center><hi>400 Bad Request</hi></center>




I am getting no data posted, and the Request log sits empty with the "waiting for requests area" just cycling. Where have I screwed up? I could send you any additional information you request, if needed

tombrew (author)  lenny20204 months ago

Hi Lenny,

Sorry, that sounds frustrating! Let's look over your code on a direct message.

davemack tombrew2 months ago

I have also just built this and get this message when it tries to send data to Xively. Perhaps I have the same issue as Lenny.

2014-07-21 14:45:04 UTC-4
Posted to Xively: 71.60, got return code: 56, msg: <html>
<head><title>400 Bad Request</title></head>
<body bgcolor="white">
<center><h1>400 Bad Request</h1></center>

davemack davemack2 months ago


With Lenny's help I found the problem! The Feed ID is a number and should not have quotation marks around it.

My unit now works.



lathyrus11 months ago
Wow! Despite not having soldered anything for about 30 years, I was able to build this thermometer without any real difficulty in a couple of hours, and I understand how it works! Thanks Tombrew for the excellent instructions. The only problem I had was that the guy in Maplins gave me the wrong size fixed resistor, so the first time I built it the reading in my livingroom was a chilly -159 degrees C... but with the correct 100k Ohm resistor everything is fine. I also couldn't get blinkup to work with my Sony Android phone so I had to borrow my wiffe's iPhone to do the setup. And getting Xively (Cosm) to draw graphs was tricky until I figured out that I needed a MASTER API key, available under the Settings tab.
lathyrus lathyrus2 months ago

Follow-up: The tempbug has been running smoothly in my attic for 9 months now. My first 9 volt battery lasted only a month, checking the temperature every 15 mins. So I changed the interval to 2 hours and my second battery lasted 6 months. I also noticed that the first temperature reading in each cycle is a bit higher than the others (by about 0.5 degree, I don't know why) so I modified the code to ignore the first reading and average the next 10:

2014-07-14 06:00:08 UTC+1[Device]ignore: voltage: 3.315 temp: 19.4 C2014-07-14 06:00:08 UTC+1[Device]loop: 0 voltage: 3.313 temp: 18.9 C2014-07-14 06:00:08 UTC+1[Device]loop: 1 voltage: 3.311 temp: 18.4 C2014-07-14 06:00:08 UTC+1[Device]loop: 2 voltage: 3.311 temp: 18.2 C2014-07-14 06:00:08 UTC+1[Device]loop: 3 voltage: 3.311 temp: 18.1 C2014-07-14 06:00:08 UTC+1[Device]loop: 4 voltage: 3.313 temp: 18.2 C2014-07-14 06:00:08 UTC+1[Device]loop: 5 voltage: 3.309 temp: 18.3 C2014-07-14 06:00:08 UTC+1[Device]loop: 6 voltage: 3.311 temp: 18.2 C2014-07-14 06:00:08 UTC+1[Device]loop: 7 voltage: 3.313 temp: 18.2 C2014-07-14 06:00:08 UTC+1[Device]loop: 8 voltage: 3.311 temp: 18.6 C2014-07-14 06:00:08 UTC+1[Device]loop: 9 voltage: 3.311 temp: 18.1 C

Building and programming the Imp was so much fun that I bought 2 more and made a phone-controlled electric gate opener, and a gizmo for forcibly rebooting my Wowwee Rovio...

Thanks again Tombrew for the great intro and instructions!

HandyFrank3 months ago

I've been wanting to create a wifi thermometer for a while, this plan looks perfect! I'm a newbie when it comes to building electronics so I have a few questions if you can share some knowledge.

Are the 2 breakout boards you link to different from each other, or one an older version or something? I noticed one is the April breakout and is green, and the other just lists as a plain breakout board and is red. Any different and is one better than the other? I see in your pics you used the green april breakout board I think.

Any way to add a humidity sensor into the mix? Would that require a whole set of different details, or can it be blended into the existing coding and add either a combo temp/humidity sensor, or a separate humidity sensor?

I can in theory build this on a mini breadboard before doing any soldering, right? Maybe i'll do that and practice my soldering skills on a test board so I don't mess up the breakout board.

Any recommendations on a soldering iron that is decent, but won't break the bank for someone who hardly does soldering? Any tips on resources for getting into learning more about how all of this works? I'm a complete newbie so I can use tips on soldering, recommended entry level equipment, understanding of circuits and all the components, etc. I see that Amazon (and AdaFruit) sell breadboard starter kits that mention Arduino. Is that a good thing to buy to start playing and learning? Is Arduino way harder to use vs. Electric Imp?

Seems like DigiKey has everything needed to build this, I think i'll order from them.


tombrew (author)  HandyFrank3 months ago

The green and red breakout boards are identical - use either of the ones I linked to.

This instructable doesn't cover what you need to do temperature and humidity sensing, but you might take a look at the electric imp reference code for the DHT11:

You certainly can build this on a breadboard, but you'll need to make sure you get an electric imp breakout board with headers, or put headers on your breakout board. You should check with google for the best soldering iron recommendations; I've got a pretty nice one and am therefore spoiled.

Arduino vs. Electric Imp isn't really harder/easier; they're different device with different purposes. I can't speak to much on Arduinos goals as a project or tool, but I can say the Electric Imp is made specifically to connect things to the internet, and it does that quite well.

Best of luck and have fun!

illiac44 months ago

I have made it but it shows around 80. I assume thies is in fahrenheit. What do i need to change that it will be displayed in celsius? TNX

tombrew (author)  illiac43 months ago
Yep, it defaults to fahrenheit. You can change it to celsius by calling "read_c" instead of "read_f" on line 103 of the device code.
dbehman4 months ago

Excellent article! I'd like to build this for a swimming pool thermometer. Do you think this would work with the sensor submerged?

tombrew (author)  dbehman4 months ago

I think it could (not the imp and power supply, though!) The longer the leads on your thermistor, the less accurate it will be. A creative mechanical design could help, or you could look into thermocouples.

byron1124 months ago

hi im trying to build the temp bug and i have it all wired up and i have used the imp before to turn on and off a light. but now that i have it programed and all hooked up and cap hooked up the right way. the imp card blinks red 3 times then flashes green for half a sec then it turns off. what does this mean??? Ive tried powering it via usb and 9v battery. same thing... any help would be great!

tombrew (author)  byron1124 months ago

That's actually just it working! The three red blinks are the imp attempting to connect to your WiFi, the one green blink happens when it connects. As soon as it connects, it runs the entire firmware and uploads the measurement in about a second, then goes to deep sleep - which is why you see it stop blinking. You should see it do this once every 15 minutes.

ai4px6 months ago

THanks.... just what I was looking for! Didn't even know about IMP.

365nice made it!7 months ago

A quick follow up - I added 3 sensors to measure temperature at several points (which works reasonably well). Note: the imp libraries have been changed - with new agent code that runs on a server to connect to Xively (was Chosm). There are examples on the imp site. This said - this was the article that inspired me - so thanks!

ygodnik 365nice7 months ago


I saw that you added sensors. I am reasonable at making circuits, but am very poor at coding (basic python and a matlab experience). I have two questions. Could I see a copy of your code? Also, if someone is fairly illiterate in coding, is there a place one can go to get the basics on squirrel? I look online and what I find is, which assumes a solid level of coding knowledge initially. It is like he is trying to explain how to speak chinese to me in swahili. I would really like to learn some nuts and bolts so I can modify things and trouble shoot reasonably intelligently.

For example,

therm_en_l <- hardware.pin8;

In this command, it seems like "therm_en_I" is one piece, but is it an built in command? I see the "<-" piece and I don't know what it means. It seems like the "." links objects together, but I am not sure when it is allowed, how it functions, etc.

Thank you for your time, and thank you to the author for the tutorials.

tombrew (author)  ygodnik7 months ago
Hi ygodnik,

I actually did link to the source code for the project in the instructable - it's all at

The line of squirrel you referenced is not a built in command; that line "aliases" the hardware.pin8 object with the name "therm_en_l".

I don't know of any really good squirrel-specific tutorials, but the language is in many ways similar to javascript. There are a boatload of places online to learn how to write decent javascript for free.

Thanks for the feedback and good luck!
ygodnik tombrew7 months ago

Thanks a bunch Tom. I did get everything working with one sensor, but I am afraid if I tried to change to much in your script with my current knowledge, I would just get myself in trouble. I will learn Javascript for dummies and then come back and see if I can get multiple components and new configurations figured out effectively.

Thank you again for the excellent program (with helpful comments) and for your help here.

discostu9567 months ago
Very nicely written. Answered questions that popped up along the way, and explained why you used what at each step. Learned a lot reading this. Thanks for such a good instructable, look forward to making one
(removed by author or community request)
tombrew (author)  smilesfromnowhere8 months ago
Hi smilesfromnowhere,

I've just pushed a small update to the github code that removes a deprecated call that may have caused errors device-side. I'm running this code on my own tempbug right now and things are working properly.

I also added two things to the agent code:

1. The agent now logs the data sent and the return code and message from Xively when attempting to PUT to the feed.

2. The agent now appends the device ID from the specific tempBug to the Xively channel name. This allows you to have many tempBugs on a single Xively feed, so you can view all the graphs on one page if you want.

Give this a try and let me know if trouble persists. If nothing else, logging the response from Xively should give us something to go on.


I was an *idiot*. The original problem was from having the feed id and the api key switched.

I get errors with the new code:
"the index 'resp' does not exist"
"at postToXively:152"
"from unknown:159"

...I have multiple thermistors wired up to this board but don't know how to 'instantiate' four different thermistors (yet).

Best Regards,
tombrew (author)  smilesfromnowhere8 months ago
No worries! I've published things with bigger mistakes than that ;)

Have you pulled the code from github again since you switched the Xively parameters back? I believe I pushed a fix for the error you're seeing above.
petewa8 months ago
built one of these the other day... love it... i have already ordered the supplies to make 3 more. this way i can monitor the temp in different parts of the house... i heat with wood so this is PERFECT! First time ever soldering anything and it worked when i was done! hehe.....thanks
frank5639 months ago
Great project, ordered directly from your list and went through the steps. It's been 30 years since I tinkered with electronics and this took about 2 hrs from start to end. I use this to monitor a summer rental property about a mile away that sits all winter, so with this, I can monitor the heat without making a trip over. Plus, it uses my neighbors wifi near the rental property!
ghwood9 months ago
This is very neat and my first Imp project. Spectacular documentation. (I actually built 2 off the bat using exactly the parts list you provide.)

For both, I seem to get through all the steps successfully but then repeatedly get the following log messages in the Electric IMP IDE (timestamps about 5 sec apart) :

2013-12-21 20:40:48 UTC-5: [Status] Device booting; 4.68% program storage used
2013-12-21 20:40:48 UTC-5: [Device] imp.configure command is deprecated
2013-12-21 20:40:48 UTC-5: [Device] ERROR: the index 'temp_sns_en_l' does not exist
2013-12-21 20:40:48 UTC-5: [Device] ERROR: at main:127

I'm hoping to present one as a Christmas gift to my father-in-law as a wine cellar monitor he can peek in on while he travels, so would welcome any thoughts about what's going on! Thank you.
tombrew (author)  ghwood9 months ago
Terribly sorry for the inconvenience, ghwood - there was a silly bug that is now fixed. Thanks for letting me know about it and Merry Christmas to you and your father-in-law.
ghwood tombrew9 months ago
Thank you! Likewise and I'll add a Happy New Year.
stealth321 year ago
Excellent solution, however i want to know if i can add more than one temp sensor, in case its positive, how many?
And about the length of the temp sensor wire, what is the max length i can use without affecting the accuracy of the measurement.
Thanks in advance.
tombrew (author)  stealth321 year ago
The imp card has six user-accessible pins, so you could set a device up like this to use as many as five thermistors directly. If you want to read more sensors with a single imp, you could consider setting up an I2C bus and using some simple I2C temperature sensors.

Any length of wire affects the accuracy of the measurement, as that wire is going to have a finite and temperature-dependent resistance not factored into your temperature calculation. I built this device primarily to show me, plus or minus maybe half a degree, what the weather is like in front of my house. With that purpose in mind, a foot or two of wire isn't going to cause you much grief.

If you're looking for accurate temperature measurement, you should really go for a digital temperature sensor.
Hi Tombrew,

I really want to thank you. This instructable helped me more than you can imagine. I have multiple imps in their own clear cases sending me temp data which I watch on Xively, and I could not have done it without you. Thanks!

Regarding this thread, my project is to set up multiple imps monitoring a bunch of solar hot water systems in my area. Each Imp will need multiple thermistors so that I can monitor independent fluid temperatures.

Last night I tried editing your code to work with multiple thermistors, but I obviously do not understand the code well enough. It didn't work. I will keep at it, but...

...I'm just curious if you have another version of the code, say monitoring 3-5 thermistors? Or, could you take a minute to type some basic instructions on how to approach adding more thermistors to your code? No worries if you are too busy. Just wanted to ask.

The Sustainability Workshop
Ithaca, NY
tombrew (author)  Sustainability Workshop10 months ago
Hi Ithacans!

The code on here has actually become a bit dated in the last few months.

I've actually taken the thermistor code and put it into a class that you can instantiate as many times as you want. Check it out here:
rob-atl tombrew9 months ago
I've been studying this code which I think is meant to handle multiple thermisters. I'm struggling though. Perhaps if you could show us code to measure & calculate 3 thermisters, and then go back to sleep 15 min, and maybe even send data to xively? That could REALLY answer most the questions folks have had, and update for xively website. What a great tutorial this is!

For example, in your revised code, you say
instead of the old code

But I was assuming 4 wires would be soldered together in hole 9? (to power the 3 thermisters every 15 min)? Or would you solder the other 2 thermisters in 5 & 7, and 1&2? If so, I'm not clear what keeps the power on for them.

If you possibly could show us a 3 thermister version of the entire example code, I think it would help us understand how this works:) THANKS!! Rob
tombrew (author)  rob-atl9 months ago
Hi Rob,

Sorry for the long wait to get this updated for you - it's been quite a busy time. Are things going better in your effort to read multiple sensors? There's a quick schematic that shows how to (and how not to) wire it up at

Now that the code is wrapped up in a class, you can just instantiate multiple thermistor objects on different pins once it's wired up correctly.

Hope all is going well.

rob-atl tombrew9 months ago
Hi Tom,
I just got my IMP yesterday, and just finished soldering up a 2 thermister version (with the help of you and Sustainability Workshop).

I don't really understand the New "AGENT version" of the code. I bet it would help novices like myself if you could possibly post 2 versions of the code?
a. The version already posted.

b. A version showing the PIN NUMBERS and where & how they show up in the code, and the resister & electronic part variables for your datasheets (THEN, I could see clearly WHERE all the PIN 9 references are, to better understand where the enabling pin # gos, that correspond to your PHOTO (Enabled pin 8 & sensing pin 9).

I see lots of PIN references, and NULL and "0"s, but don't know the conventions for entering MY PIN NUMBERS & CONSTANTS from MY datasheets. One example with actual pins from your photo is all we'd need.

Hope this is clear:) Thanks for the great support so far.
tombrew (author)  rob-atl9 months ago
Hi Rob,

The new code is a little longer, but it's actually pretty well-commented and modular - have you given the source itself a look?

The values for your thermistor from your datasheet are stored as consts at the top of the device code - see line 33.

The pins numbers are assigned on lines 117 and 121:

therm_en_l <- hardware.pin8;
// pin 9 is the middle of the voltage divider formed by the NTC - read the analog voltage to determine temperature
temp_sns <- hardware.pin9;

Don't edit anything inside the class definition; this is a generic set of instructions for how to operate a thermistor, and it doesn't ever need to change. You work with it just by passing different parameters into the constructor when you instantiate it.

The short version:

1. Your datasheet variables go at the top near line 33.
2. You only need to change two lines to set your pin numbers: 117 and 121.


tombrew (author) 9 months ago
Hi all, a couple of quick updates for you.

1. I've just refactored this instructable to use electric imp's *agents* feature, and to use Xively (the new Cosm) since Cosm is long-gone. It looks quite a bit different, but it's way more powerful. I hope everyone will enjoy this.

2. The question about reading multiple thermistors has come up a bunch of times, here and elsewhere, and it got some good attention on the electric imp forums, here:

Happy hacking!

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