This alcohol sensor is suitable for detecting alcohol concentration on your breath, just like your common breathalyzer. It has a high sensitivity and fast response time. Sensor provides an analog resistive output based on alcohol concentration. The drive circuit is very simple, all it needs is one resistor. A simple interface could be a 0-3.3V ADC.
This sensor has a high sensitivity and fast response time. The sensor's output is an analog resistance. The drive circuit is very simple; all you need to do is power the heater coil with 5V, add a load resistance, and connect the output to an ADC.
For an example project, check out Shawn's tutorial:
Checking with a multimeter and it does not matter if it's A or B on any of the gas sensors that is connected with the breakout board. If you look at the datasheet, it shows that the pins for A1 and A2 or B1 and B2 are internally connected together, respectively. Also the application circuit shows that the polarity does not matter, just as long as the pins on each side align with the breakout board.
This skill defines how difficult the soldering is on a particular product. It might be a couple simple solder joints, or require special reflow tools.
Skill Level: Noob - Some basic soldering is required, but it is limited to a just a few pins, basic through-hole soldering, and couple (if any) polarized components. A basic soldering iron is all you should need.
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If it requires power, you need to know how much, what all the pins do, and how to hook it up. You may need to reference datasheets, schematics, and know the ins and outs of electronics.
Skill Level: Competent - You will be required to reference a datasheet or schematic to know how to use a component. Your knowledge of a datasheet will only require basic features like power requirements, pinouts, or communications type. Also, you may need a power supply that?s greater than 12V or more than 1A worth of current.
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So, I've been working on figuring out how exactly determine BAC from this little guy, and its been an interesting journey.
First I went through the Datasheet, which is all about the resistance ratio of the sensor element of a sample of fresh air (R0), and a the unknown (RS). Everything is about RS/R0. as that fraction gets smaller the measured alcohol goes higher.
I have two problems with the Rs/R0 approach. Firstly, R0 is not a stable number. The longer the heater is running, the higher the resistance, and it seemed logarithmic, over time, never approaching a single value.
My second issue with the Rs/R0 approach, is that there is not solid data in the data sheet(there is a graph) that maps a certain ratio to a parts per million (ppm) measurement.
So after I abandoned the Rs/R0 approach, I decided to use the standard law enforcement formula (BAC = breath mg/L * 0.21). I decided to do one measurement at an equivalent .08 BAC, and another data point at .16 and a third at .24. This actually produced the best, and most predictable and consistent results. I took a 1/4 tsp of 91% rubbing alcohol and mixed it into 35 oz of tap water (1000:1 mixture). Then I used a 5.55 Liter bottle I had, and after cleaning it out, would pour 1/2 tsp of the 1000:1 mixture in, and read that as .08 BAC. I would then add another 1/2 for .16, and a total of 1.5 tsp for .24
So, after all this, I thought I was spot on, and knew how to measure effectively a .08.
Not so fast.
The temperature of this sensor when measuring affects everything. And when you blow quickly on it, the temperature and the resulting reading goes lower than it should, and will actually spike when you stop, because it warms up and registers the alcohol that is still present. Conversely, if you open your mouth wide, and blow hot moist air, the reading is exaggerated in the other direction.
My next step is to build a T shaped straw, with the sensor not getting hit directly by the breath, therefore minimizing the cooling/heating effects of the breath.
As I learn more, I will add my comments below.
Very good and fast service, price is accepable. Sensor fits to Alcosafe kx-6000S4. Many thanks!