Hi
Can anyone help? I need help with board design and programming. I'm looking for a board that will read two temperatures. If temperature A is greater than temperature B then a contact is closed and if temperature A is less than temperature B then the contact opens and finally if temperature B goes below 17 degrees regardless what temperature A is the contact will open. Any help would be much appreciated thanks.
Gavin
Obviously you need two temperature sensors. What absolute temperatures are you measuring ? If below about 120C thermistors are cheap and accurate to 1C or so.
regards
Allan.
Hi
Thanks for your input, I'm measuring indoor and outdoor air temperature throughout the year in the UK.
any board will do.
most temperature sensors are only good for about 1 deg C without some calibration on your part.
also, sun on a sensor will effect the reading. there is a building envelope heat that is radiated from the building. much more on the sunny side that gets hot from the sun, then releases the heat over time.
That said, you have a wide range of choices.
an Arduino nano, uno, etc is fine
a DS18B20 is a low cost sensor that requires almost no work on your part and the readings are serial so even less area for you to mess things up.
the DHT11 offers temperature and humidity.
any Thermistor, we usually use a 10k version, with a matching 10K resistor.
there are some other higher resolution higher accuracy devices, but as you start to get more accurate, your design, wires, etc start to add possible errors. your long wires might act like an antenna, etc.
but the LM35 chip reads in deg C and you can calibrate the heck out of it ( heck is slag for errors )
also simple to use.
If I wanted to that that ASAP, I would use either the DS18B20 or a 10k thermistor for fast and easy. get a relay and you can turn things on and off and Bob's your uncle !
Once you want to add more, get a LCD shield and you can get readouts.
up to this point all you need is the above and a simple 9v or 12v power supply, or an old cell phone charger that outputs 5v
everything you need can be found by googling
arduino DS18b20
arduino relay
what you did not mention was WHAT you wanted to turn on and off.
you might be better to get a 5V plug in power supply and a 5 volt relay.
or a 12V power supply and a 12V relay.
Relay power is separate from the Arduino, but they can be on the same power supply.**
the Arduino can take 5volts, or you can feed it 9 or even 12 volts DC.
if your device is 12 volts, you can power the relay from that 12V.
** power supply goes to the relay board directly.
also goes to the Arduino directly
NEVER, repeat NEVER try to power a relay from any part of an Arduino.
Also, a capacitor on both the relay input and the Arduino input will help with any noise on the line.