I have built the heart rate circuit and it works. My problem is interfacing a temperature circuit to the Adruino Mega. I am having difficulty finding a circuit that will interface with heart rate circuit and arduino mega.
At last count there were a gazillion options for temperature measurement... I've used a LM35 with good results previously. They are very cheap, easy to interface, and pretty accurate. But do some research to find something that fits your requirements.
Cheers,
G.
finding a circuit that will interface with heart rate circuit and arduino mega.
What has the heart rate circuit got to do with it? The temperature measuring should be considered completely separately.
You can also use just a plain old thermistor and fixed resistor arranged as a potential divider connected to an analog input.
This will be accurate, but you will need to do some maths to turn the voltage into degrees.
There is an example sketch here (Project 13). http://www.arduinoevilgenius.com