I am working on a gas/fire detector project using a Raspberry Pi 2. I would like to gather input from the following sensors:
Adafruit AM2302 (wired DHT22) temperature-humidity sensor MQ-2 Gas Sensor MQ-7 Gas Sensor Universal Sensor 595391 (IR flame sensor)
For the last 3 sensors (which require an analogue input) I have also purchased an MCP3008 analogue to digital converter. Right now I have the AM2302 hooked up and recording temperature/humidity data through wiringPi and storing it in MySQL.
I would like to add the other 3 sensors and record data through wiringPi to be stored in MySQL, but I have had a lot of trouble finding anything about whether or not these 5V sensors will need a voltage divider before connecting to the MCP3008.
When reading the datasheet for the MCP3008 the specifications say that the chip can operate with a power level between 2.7 to 5.5 volts, but I am not sure if the output to the Pi's GPIO pin will exceed 3.3 volts and cook it if the MCP3008 is hooked up to 3 sensors running 5 volts.
I have also read that the MQ-X sensors or at least the MQ-7 can run on 3.3 volts which runs contrary to its data sheet - see Digital sensors and the Raspberry Pi with the smoke detector MQ-X as example.
My question is: How should I connect these sensors to be used on the Raspberry Pi 2 in order to be read through wiringPi?
I am new to working with Raspberry Pi GPIO so any help would be greatly appreciated.