Maddy from Little Bird Electronics suggested I go direct to the experts so here goes..
My requirement is:-
20 Rooms temperature to monitor
In Place:-
We currently monitor these rooms back to a patch panel that displays this info. Using TP2000 Probes. These use resistance which from the output of the dislpays creates a output voltage which I wish to use as input.
New Requirement:-
If the Temp gets above or below n degrees C a SMS alert is sent to a tech.
Data to be logged on a pc.
I can code any program for the data logging / sending alerts etc but electronics is not my strong point. Intermediate understanding though. (Plus google).
It has been suggested to use the Arduino Mega 2560 along with a ArduinoGSM Shield (for connectivity / sms).
Issue..
As this Arduino board only accepts max 5v as input (able to have 50 inputs) how can I step the voltage down.
Ie.
If the shed is 30 degrees c then the input will be 5v
If the shed is 15 degrees c then the input will be 2.5 etc etc..
Is the Arduino the answer to use along with sonething to step the voltage down for input.. or is there something better that may meet my needs.
Regards
Mark
Best Answer
You are saying you need to step down the voltage, but then you are describing the voltage levels as if they range from 0 to 5 volts. Is the voltage range of your signals 0 to 5V? If yes, then you can used the A/D converters that are built into the AtMega2560. If you have more inputs than supported by AtMega2560, you can use an analog switch, such as 74HC4851. I don't know how the analog inputs are configured on the Arduino board, you might have to use Op Amp configured as unit gain as a front end. Also, you might want to use zener diode to limit the voltage to 5 volts.