Wireless signalling for a temperature sensor

[Tim4444]

Hello, 

I am trying to build a temperature sensor which is situated outside and sends a signal to a display screen inside.  I am trying to do this as an electronics project and would like to do it all from scratch.

Can anyone please give me some advice into how I would get the signal from outside to inside without using a wire?
I am assuming that I can buy two small devices that send a signal to another.  Can you get things like this that are fairly cheap?

Thanks

Tim

[Balaur]

You can buy a relatively cheap (<$5) RF Transmitter & Receiver kit for Arduino.

I would imagine that a solution could be as follow: low cost *duino + temperature sensor + transmitter > receiver + *duino + display.

This solution may not be cost effective when compared to a commercial wireless weather station that you can buy from Walmart. Of course, buying some pre-made modules hardly classifies as building something from scratch, right. Yes, you may learn something, of course, but there are more interesting projects.

[Maxlor]

A couple of methods come to mind:

• The cheapest way would be to use an IR diode and photoreceptor. If the two parts of your project are afixed to either side of a glass window, this would work well, and is very cheap. On the other hand, then you might as well just add the display to the outside part and leave away the receiver altogether...
• A more expensive way would be to use some RF module. Maybe a plain Bluetooth one like the RN-42; they're quite easy to use and you can connect to your Android phone.
• Or use a Bluetooth 4.0 module based on the CC2540 to connect to your iPhone or one of the Androids that supports Bluetooth 4.0.
• Or one of the many Zigbee modules. The cheapest such module I'm aware of is the MRF24J40MA (although strictly speaking it doesn't do Zigbee without additional firmware that costs extra, or that you need to write itself; however you can use MiWi instead, or just plain 802.15.4 which the module does in hardware.) They're a bit harder to use, and full Zigbee modules are quite a bit more expensive though, especially since you'll need two of them.

[w2aew]

One inexpensive arduino+wireless alternative is the Moteino (http://lowpowerlab.com/moteino/).  I've used these a few times, and they work really well - and are very inexpensive.  I did a little video overview several months ago.  I don't have any affiliation with them, but thought it was a cool product. You could mate this with a temperature sensor on the remote side, and a LCD display on the other, and you're good to go:

[Galenbo]

The solution I know: DS18B20 + PIC + Zigbee or Bluetooth.

I'm not saying it's better. It's the only one I "really" know.

[babysitter]

Or you might go with a Bluetooth LE module like BLE112, which has the temp sensor integrated and doesnt need much besides a battery (coin cell is sufficient for transmitting you long time), and at the inside you might test receive it with a smartphone before you go and dedicate a second module for a display ?

[Tim4444]

Thanks for the help everyone.  I see that there are quite a lot of options.

I shall have to have a think

Tim