The Homebrew Optical Sensor helps you pass the diesel smoke test

We’ve all heard of smoke testing, and we know it’s the lowest possible time for the performance of an electronic device. If it does not explode in the fire while applying the force, you can go for a more effective test. But smoke testing means something else for the car, especially powered by diesel fuel. And passing the diesel exhaust test can become something of a job.

To make it easier to pass these tests, [Janis Alnis] He has come up with a diesel exhaust monitor that measures the opacity of his car’s emissions. The sensor itself is quite simple, and mimics what a commercial exhaust analyzer uses: an LED and a photodiode at the opposite end of a tube of a certain length. The exhaust particles passing through the tube will scatter light in a predictable way and the numbers prove that the passing grade is 53% more than the transmission.

The sensor body is assembled from a brass pipe fitting with epoxy glass windows at each end. The exhaust enters through a T-fitting attached to a hose and sampling tube and exits through the other T. One window of the sensor has a cheap battery-powered flashlight as the light source, the other end has a Texas Instruments OPT101 photodiode sensor. The sensor is connected to one of the Arduino’s analog inputs, which drives a 128 × 64 pixel LCD display – inspired by this air quality meter – to show current smoke graphically and as a percentage. The video below shows the sensor working.

Although there were some problems in making ink using sensors and condensing water vapor [Janis] It has been discovered that the little bit things on a warm-up drive have become hot enough to clear up some of his ride’s smoking tendencies, allowing him to pass his inspections.

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