One reads the temperature using a DS18B20 and then transmitts it over the radio waves.
The other receives the data and displays it.
I've not fully tested the range yet, but I've had it working over 12 feet going through 2 walls.
Transmitter Parts List:
- Picaxe 08m
- DS18B20 temp sensor
- AM RT4-433.9 transmitter module
- 4k7 resistor
- 1k resistor
- 3.5v Battery
- Picaxe 18X
- AM HRR3 433.9 Receiver module
- 7 segment I2c module
- 5mm 2 pin Bi-Colour LED -- red and green
Step 1: Build the circuit
The transmitter circuit is shown at the top, I actually didn't use 5v, instead I ran it off a 3.5v button battery. The button battery was hooked up to a solar cell; a module I pulled from a cheap solar torch. I've had the transmitter circuit lying on my window sill, happily transmitting for a week with no power problems.
The AM transmitter/Receiver I had bought years ago from Maplin.
The receiver circuit is shown below, it is very simple. Pins 11 and 12 on the chip is actually a bi-colour LED, I wasn't sure how best to draw it.
The counter looking object in the top right makes displaying a number easy work. I needed a chip that could use the I2C, which is why I'm using a Picaxe18X. The 7 segment module was bought off ebay for about �15, but they do sell it on their website
I've not shown the programming header, partly to keep it simple and clean and partly because I was using a seperate circuit to program the chip.