Homebrew Optical Sensor Helps Your Diesel Pass The Smoke Test

June 27, 2022 by Dan Maloney 50 Comments

We’ve all heard of the smoke test, and we know that it’s the lowest possible bar for performance of an electronic device. If it doesn’t burst into flames when power is applied, you’re good to go for more functional testing. But the smoke test means something else for cars, especially those powered by diesel fuel. And passing diesel exhaust tests can become something of a chore.

To make passing these tests a little easier, [Janis Alnis] came up with this diesel exhaust monitor that measures the opacity of his car’s emissions. The sensor itself is quite simple, and mimics what commercial exhaust analyzers use: a LED and a photodiode at opposite ends of a tube of a specified length. Soot particles in exhaust passing through the tube will scatter light in a predictable way, and the numbers work out that a passing grade is anything greater than 53% transmission.

The sensor body is cobbled together from brass pipe fittings with glass windows epoxied into each end. Exhaust enters via a tee fitting attached to a hose and sampling tube, and exits through another tee. One window of the sensor has a cheap battery-powered flashlight as a light source, while the other end has a Texas Instruments OPT101 photodiode sensor. The sensor is connected to one of the analog inputs of an Arduino, which also runs a 128×64 pixel LCD display — inspired by this air quality meter — to show the current smokiness both graphically and as a percentage. The video below shows the sensor at work.

While there were some issues with soot buildup and water vapor condensation, using the sensor [Janis] discovered that a little bit of a warm-up drive got things hot enough to clear up his ride’s tendency to smoke a bit, allowing him to pass his inspection. Continue reading “Homebrew Optical Sensor Helps Your Diesel Pass The Smoke Test” →

Here’s The Dirt On Printing With Pollution

March 5, 2014 by Kristina Panos 34 Comments

[Anirudh] and his friends were sitting around reminiscing about India. In particular, they recalled riding around in auto-rickshaws in stifling heat, watching their skin turn black from the exhaust. They started thinking about all of the soot and pollution in crowded cities the world over and wondered whether the stuff could be re-purposed for something like printer ink. That’s how they came up with their soot/pollution printer.

They created a soot-catching pump which they demonstrate with a burning candle. The pump mixes the soot particles with rubbing alcohol and an oil substrate and sends the ink to an HP C6602 inkjet cartridge. They used [Nicolas C Lewis]’s print head driver shield for Arduino to interface with the cartridge, turning it into a 96dpi printing head that uses only five pins.

[Anirudh] and his friends plan to design a carbon separator using charged plates to capture the soot particles from pollution sources and filter out dust. Be sure to check out their demonstration video after the jump.

Update: In response to [Hirudinea]’s comment about mining the carbon from cars, [Anirudh] is now looking for collaborators (tinkerers, filmmakers, DIY enthusiasts) to move forward with the idea of re-purposing carbon. Email him at anirudhs@mit.edu.

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Geek Group Fire Update

January 6, 2014 by Adam Fabio 167 Comments

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The Geek Group is in the process of cleaning up after their fire. Their small capacitor/spark gap room sustained the most damage, with the interior nearly completely incinerated, along with some structural damage to the walls and roof. The gap room was isolated from the much larger high voltage lab by red plastic welding curtain. The curtain was fire-retardant, but when it did finally burn, it was extremely sooty. With the curtain burning, soot covered the high voltage lab. The rest of the building escaped fire damage, but nearly all of it is covered in a fine layer of soot. The group has been and are attacking the soot problem head on, with shop-vacs, rags, and elbow grease. Several of their sponsors have also promised supplies to cover the remediation.

[Chris] and [Paul] have also been doing some sleuthing as to the root cause of the fire. While the cause will never be known beyond a shadow of a doubt, they have a pretty good idea of the chain of events. Gemini, the group’s 200 kVA Tesla coil had been run about 1/2 hour before smoke was detected. The fire was concentrated in Gemini’s spark gap room. Close inspection of the rotary spark gap showed that the stationary electrodes all seemed to have sustained a mechanical impact. It appears that either while the gap was running, or as it was spinning down, one of the flying electrodes moved enough to impact the stationary electrodes. These electrodes are 3/8″ and 1/2″ tungsten, and often glowed white-hot while the gap was in operation. One set screw held each electrode in to the 12″ rotor. The set screw of one flying electrode was found to be loose, and the electrode it retained probably impacted the stationary electrodes. It’s not a far leap to guess that hot metal from these impacts could have landed in the capacitor array, smoldered, and eventually caught aflame.

A single loose screw most likely caused the entire chain of events leading up to the fire. [Chris] and [Paul] had observed the spark gap throwing out hot bits of metal even during normal operation, and had planned an encapsulation box. However, disaster struck before it was built. This is not to say that The Geek Group operates an unsafe shop. The important thing here is that no one was hurt. Everyone in the building was evacuated quickly and safely.

A quick note about the comments – we know The Geek Group and [Chris] tend to be polarizing topics. However, we’d like to at try to keep the comments constructive.

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