Wireless Temperature Sensor with Cheap RF Modules

About a year ago I did a wireless sensor project using XBee radios. People seem to have a lot of problems configuring XBee to work correctly, so I thought I'd try using the cheap 434 MHz RF modules that cost only a few dollars. It worked just fine. The only downside is that a microcontroller is also needed on the transmitter side (not true with XBee since it has its own ADC).
The project details are here: Wireless Temperature Sensor using RF Transmitter/Receiver | Project Lab

I was thinking about doing the same thing. I picked up a water-resistant micro-case for free a while back, and I have some digital temperature sensors as well as a few ATTinies I can use on the Tx side. All I need are the receivers/transmitters and some li-poly batteries.

There might be a way to get temperature without a microcontroller at all. IIRC these RF modules are OOK (on off keyed) so any square wave will go thru. You could use a CMOS 555 timer and make an audio oscillator using a thermistor.

Transmit that, and receive it into a digital pin on the other end.

The receiving Arduino can determine the frequency of the square wave, and convert to temperature. Either a polynomial equation with a couple of calibration constants or else a lookup table and interpolation would work.

Not that your approach is bad either, nice work!

There is any possibility to send only LOW, HIGH signal from a PIR sensor using the 433MHz Transmitter without using microcontroller. I have an Arduino UNO to use it on Receiver part. I'm trying to build a “cheap security system” but I don't want wires?

PS: I'm beginner in electronics

Thanks in advance!

Cascavalpane, you probably should have started a different thread... but yes, you can probably do that. The problem is, without additional resources (or an encoded transmitter) you will only be able to use one sensor at a time.


that is such a professional writeup. Those pictures are 1st class.
Thanks for that.


with "li-poly batteries" you could consider supplying those ATTiny microcontrollers with 3.3V (instead of the Arduino's 'standard' 5V).

A blog report similar to nootropic's would be very helpful for amateur's like me :wink: