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Topic: wireless Multi-room thermometer (Read 4 times) previous topic - next topic


Hi !

I'm totally new to this Arduino stuff and I have a some quoestion. I have read a lot of topics and tutorials, so I have a some idea how to program the Arduino and how things generally work.

This is my consept:
The measuring device would have some kind tempature sensor, XBEE transmitter and a 9 volt powersulpy. There would be 5 to 10 pcs of these devices around the house.

Then there would be the dislpay/log device. It would contain Arduino, XBEE, a small screen and some data store device (a small memory card). It would be enough, if the screen could show one tempature at a time. Then there could be a button to toggle between the sensors.  I could then do the advanced analyzes at my computer with the logs.

Could it be possible to make something like that? Well I'm pretty shure that the displey/log device is donable, since someone just made similar (see next post) altough it doesn't have a display.

So the real quoestions is what parts to use in the measure device? Is it possible to use just the sensor and a radio device, or does it need more hardware?

Is XBEE the most practical solution for the wireless? Cost is not a real issue, but afcourse if something can be done cheaper and still get the needed functions. I'm also planning to document this project well, that a noob like me could repeat this...

Thanks in advance!




I'm working with a student on exactly that project. We have a protoboard version, with an Arduino connected to a DS1820 temperature sensor, a simple Honeywell humidity sensor and an air pressure sensor, and we're sending the data by XBee. I don't have the base station built yet, but we're getting data on a terminal screen without any trouble. This is definitely a doable project.


Hi Sylvie369 and Thanks for the reply.

So in your design, you have Arduino, XBEE and multiple sensors in the measuring device? Can you give me an estimate cost of one unit?


Feb 05, 2010, 07:47 pm Last Edit: Feb 05, 2010, 07:48 pm by sylvie369 Reason: 1
I'm getting paid to do mine, so I'm not trying to do it "on the cheap", so this might not be the best model, but here's what I've got:

Remote Station

Item      Number      Part Number      Source      Unit Price      Total Price
Arduino Pro Mini 5V      1      DEV-09218      Sparkfun      $18.95      $18.95
Machine Pin headers - male      1      PRT-00117      Sparkfun      $2.95      $2.95
Machine Pin headers - female      1      PRT-00743      Sparkfun      $3.95      $3.95
Lithium-Polymer battery
1100 mAHr      2      PRT-00339      Sparkfun      $11.95      $23.90
XBee Pro, Chip antenna
XBP24-ACI-001      1      32406      Parallax      $32.00      $32.00
LM2940 5V regulator      1      601-00506      Parallax      $1.25      $1.25
1000uF capacitor      1      201-01085      Parallax      $.55      $.55
1uF capacitor      1      201-01050      Parallax      $.75      $.75
Circuit board      1      (custom)      BatchPCB      $10.00      $10.00
XBee headers - female      2      S5751-10-ND      Digikey      $.87      $1.74
HIH4000001 Humidity sensor      1      480-2905-ND      Digikey      $20.91      $20.91
DS18B20 Temperature sensor      1      DS18B20+-ND      Digikey      $5.04      $5.04
ASDX015A24R Pressure sensor      1      480-1915-ND      Digikey      $32.09      $32.09
Hammond enclosure 1593QBK      1      HM359-ND      Digikey      $4.64      $4.64
Total:      $76.97

There'll be a little more stuff in there - right now I'm adding a second voltage regulator that I seem to have forgotten. You could probably bring the price down a good $10 by using a bare Arduino chip instead of a Pro Mini (which I expect to reuse in other projects). The humidity and pressure sensors are going to run you some money, so you won't get it down too far.

I had some of these parts sitting around already as well, from earlier projects.


Thanks for so accurate details, altough are you shure about the total amount?

So in my case, I could just get a
normal Arduino ~$15
the ceapest XBee ~$20
DS18B20 Temperature sensor ~$5
all the other stuff ~$10

Afcourse to by those here in Finland, or to get those shipped, the total price would go to ~$60 - $70

Do you know if it's possible to leave the arduino out from the units? Since in my case there would be only one sensor?


I'm not sure if we're talking about the same thing here. I'm not talking about a kit of parts that's available for sale. What I have there is just a list of the parts I'm using to put together into a unit. You'd have to find sources for the parts, and put them together yourself.

You're right about the price - I forgot that you're only measuring temperature. That brings the price WAY down. DS1820s are cheap (yup, $5) - it's the pressure and humidity sensors I'm using that are expensive.

There is one other thing I didn't list that you will need - a board for the XBee. I'm making my own circuit boards for this, so that wasn't a separate part of my costs, but you'll need something to mount the XBee on, some way to power it, and some way to connect the Arduino to the DIN and/or DOUT pins. There are quite a few ways to do that, ranging from the standard XBee shield to various smaller boards that just break out a couple of pins.


So according to this blog:


It is possible to hook the XBee and a tempature sensor, with out any microcontrollers. Also in the same blog, they have the recieving end built, but it's a bit too simple. Altough the basic components would be the same, Arduino, XBee shield and a XBee.

Do you think that it would be possible to have several of those simple untis and one base unit? Or does the consept of multiple sensor require a microcontroller to the measuring device?


Xbee is definately the most plug and play way to do what you're looking for, but its also one of the most expensive.

you could use an arduino, xbee shield, and xbee module on EACH sensor station AND on the reciever station if money is no issue.

I think i more pratical way might be to use the 315mhz transmitter and 315mhz reciever from sparkfun with an arduino chip, which is what i plan to do with my whole home heating and air zoning project.

your "master" station will send a request for station 1's sensor data and wait for a response. ALL of the stations will recieve this command and analyze the message to see which station it was meant for. when station one sees that the master station's message was meant for it, it will transmit a similar message stating that it is meant for the master, which will then read the message and save the sensor data from station one. Then the masrer will send a request for station 2's data, lather, rinse, repeat =)

the transmitter and reciever will run you $10, a pre-programmed arduino chip and voltage regulator components about $6, and a temp sensor about $6

so that's just over the cost for an xbee alone lol

Hope that helps!


That sound good. I'l take a look of the transmitters.

Is it so, that I can buy re-programmed chips and then use the Arduino USB Board to program those? And then use the Arduino USB Board as the base station?


If you end up with an Arduino + XBee take a look at the boards I make
that combine an ATmega168/328 and an XBee on a single PCB --

The analog sensors can be used with  standalone XBees. For longer battery life you
can run the XBees at 3V. Use a Li-ion battery and an LDO. You get about 80%
efficiency during operation and you should be at around 35uA of Icc when
sleeping. I just did a write-up on this. See  http://wiblocks.luciani.org/white-papers/intro-to-zigbee.html

(* jcl *)

www: http://www.wiblocks.com
twitter: http://twitter.com/wiblocks
blog: http://luciani.org
www: http://www.wiblocks.com
twitter: http://twitter.com/wiblocks


I think I'l try to use the 433mhz units, cause they are cheaper and if I use my own Arduino chip, the cost might stay down and I would have more functionaly.

I red a lot about the ATmega328 and I think my design is ok. Here's a few pics:

Next step is to attach the thermo-sensor, radio transmitter and reciever.

So what pin would be the best for a Dallas DS18B20 digital sensor?


I think I found the right pins for the transmitters. My question is that can I also use ATmega pins to power up the transmitters and the sensor? If I could, then I can preserve power by setting those pins to LOW when they are not needed.

This is my pin configuration:

1      to reset button
2      to RF reciever
3      to RF transmitter
7      to AVCC pin 20
8      to GND pin 22
9      to crystal
10      to crystal
11      power for sensor
15      power for transmitter
16      power for reviever
18      digital for sensor
20      to AREF pin 21
21      to 5v
22      to 5v GND

Can I just use any pin for power, or should I use specific pins? What pin is the correct one for the digital sensor?

Can the RF-modules be close to gether, like this?


Feb 08, 2010, 11:05 am Last Edit: Feb 08, 2010, 11:06 am by ekto Reason: 1
I've done some rethinking of the project and I decided to go with three AA-batteries. Those suply 4.5 voltage and around 2500 mAh. This way I can remove some components.

My worry is power consumption. Can you guys provide any power consumption numbers of the Atmega 168 or 328? I didn't fine any from the datasheet or by google.

If I can power the transmitters and sensor from atmega, then I think that their power consumption would be really low, since they would run only when needed.

The digital sensor uses like 2 mAh, but if the update is every 30 sec and the sensor runs only one sec, then the real consumption would be 0,016 mAh. The radious would propaply need to be used longer, so their consumption would be something like 0,2 total.

If the total consumption would be like 0,5 mAh, it would mean that the batteries would last about 6 months. So any idea how much does those atmegas take?

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