DIY Rechargeable Alcohol Detector
Introduction: DIY Rechargeable Alcohol Detector
Hi friends, we are back with an easy DIY project. Today we will be building a DIY rechargeable breathalyzer. As we all know, breathalyzers use the amount of alcohol in exhaled breath to calculate the amount of alcohol in a person's blood. In this project, we will be showing how to build a breathalyzer on your own. Now what? Let's get building.
Step 1: Electronic Components
These are the major electronic components required for this project.
Here is the link for purchasing these electronic components.
* 1 X Digispark Attiny85
* 1 X 500 mah Lipo Battery
* 1 X MQ3 Alcohol Sensor Module
* 1 X TP4056 Charge Controller
* 1 X SPDT Slide Switch
* 1 X Common Anode RGB Led
* 1 X Piezo Buzzer
* 1 X DC-DC Boost Module
* 1 X 2.2k Resistor
* 5m Silicone Red wires
* 5m Silicone Black wires
* 1 X PCB
* Female header
Tools
* Glue Gun
* Soldering Iron
* Flex Quick
* Vernier Caliper
* Ruler
* Laser Cutter
Step 2: Why These Components?
* Digispark Attiny 85
Here we are using Digispark attiny 85 as the microcontroller. You can use any Arduino board instead.
Here we considered the Digispark attiny 85, for making the device a compact one. Just as most Arduino boards come with a USB port for programming and sometimes as a source of power, Digispark comes with an onboard USB connector that can be plugged directly into a computer for programming of the device. The board can be powered via the USB port which will feed 5V to the board or from an external source via its VIN pin that can accept ~7 to 35V which will be regulated down to 5V through an onboard 78M05 voltage regulator.
* MQ3 Sensor Module
We used the MQ3 Sensor module for the detection of alcohol in the air. MQ3 alcohol sensor module is a great option because this module can be easily integrated into the microcontroller.
* Piezo Buzzer & Common Anode RGB Led
For alerting the alcohol presence, we used a Piezo Buzzer and Common Anode RGB Led.
* Lipo Battery
Here we used a lipo battery for powering up the project. The battery capacity is about 500 mah, so the device can run over a long time. The lipo battery has High energy density, Thin thickness, Low internal resistance, Good charging, discharging characteristics, High voltage, Good safety performance and Long cycle life.
* TP4056 Charge Controller
The charge controller used in this project is TP4056. The reasons why we used this are
1. Constant Current / Constant voltage charging method.
2. C/10 Charge termination.
3. 769
2.9V trickle charge threshold (for deeply discharged batteries).
4. Upper charge stop voltage: 4.2V.
5. Soft start inrush current limit.
6. Automatic recharge (keeps batteries optimally charged when connected to a charger).
And it's very cheap.
* DC-DC Boost Module
The microcontroller needs 5V to operate and the lipo battery can provide up to a max of 4V. That is really a big issue that's why we used a DC-DC Boost converter for converting 3.7 Volts to 5 Volts coming from the lipo battery.
And we also used a SPDT slide switch for regulating the current flow in the circuit.
Step 3: MQ3 Alcohol Sensor Module and Calibration
MQ3 is one of the most commonly used sensors in the MQ sensor series. It is a Metal Oxide Semiconductor (MOS) type of sensor. Metal oxide sensors are also known as Chemiresistors because sensing is based on the change of resistance of the sensing material when exposed to alcohol. So by placing it in a simple voltage divider network, alcohol concentrations can be detected.
MQ3 alcohol sensor works on 5V DC and draws around 800mW. It can detect Alcohol concentrations anywhere from 25 to 500 ppm. If you need more knowledge about this, please read here. The lastminutengineers made an excellent write-up there.
For the calibration process, we are using the sensor with the Arduino, because Digispark does not provide any Serial Output. So it is very hard to play around. Connect the sensor to the Arduino as per the schematics.
Use the sketch above to note what values your sensor outputs when you blow your breath on the sensor without consuming alcohol vs after consuming alcohol. Here we used sanitizer for the job because we don't have access to alcohol. 152