More info at: http://citizensensor.cc/make
To Purchase a kit, email joe: firstname.lastname@example.org
Step 1: Gather Materials and Tools
• a soldering iron
The kit includes the following parts:
• 1 MQ-7 carbon monoxide sensor
• 5 4148 300mA diodes
• 1 5v relay
• 1 3904 transistor
• 1 1K ohm resistor
• 1 10K ohm resistor
• 1 sensor socket
• 1 straight 4-pin header
• 1 PCB
If you purchased a kit and are missing any of these parts, contact joe at saavedra [at] jos [dot] ph
Step 2: 10k Ohm Resistor
Step 3: Diodes
Step 4: 3904 NPN Transistor
Step 5: 1K-ohm Resistor
Step 6: 5v Relay
Step 7: Sensor Socket - Prepare Legs
Next, bend all of the legs towards the middle. To get an idea of how far in, look at the footprint on the board. The legs will all be going into the 6 holes in a circle in the footprint of the sensor.
The reason we need to use the socket is because if we solder the sensor itself, we can damage it. The extreme heat from the soldering iron will destroy the filament inside of the sensor which will ruin sensitivity to anything. All MQ sensors are like this and should be used with a socket.
Step 8: Sensor Socket - Solder In
Be sure that all legs are inside the holes at least a tiny bit. Then, apply force with two thumbs to the top of the socket. Press hard. The legs will collapse, bending in two places. If done correctly, you'll see all tips have bent inside the hole and the legs have also bent close to the white plastic. Now, will keeping the socket in place ( you can use tape ) solder all the legs in from the other side of the board. You will want to let the solder drip all the way through the hole to get a good connection with the legs. If you mess up, it's ok - pull on the white plastic and use needle nose pliers to bend legs to the hole. You can even add solder from the top of the board while the socket is pulled up.
Make sure all legs are connected to the board! Use a multimeter to check continuity between the top of the socket and the back of the board.
Step 9: Header Pins
Step 10: Insert the Sensor and Hook Up!
Press the sensor all the way into the socket. You are ready to go!!
As you can see wire up the pins as you see in the picture:
5v -> 5v on your microcontroller
gnd -> ground on your microcontroller
tog -> a digital pin to pull HIGH or LOW (toggles 5v or 1.4v)
out -> analog input on your microcontroller. The board outputs a variable voltage dependent on CO exposure.
Download the Arduino Library with Example code for this breakout at http://citizensensor.cc/make .