Scissor Lift Shoes May Be OSHA Compliant

It’s been said that necessity is the mother of all invention. This was probably the fundamental principle behind the show “Inspector Gadget”, a story about a police agent who has literally any technology at his grasp whenever he needs it. Although the Inspector’s gadgets get him into trouble more often than not (his niece Penny usually solves the actual crimes), the Inspector-inspired shoes that [Make it Extreme] built are a little bit more useful than whatever the Inspector happens to have up his sleeve (or pant leg, as the case may be).

If a fabrication tour de force, [Make it Extreme] built their own “Go Go Gadget Legs”, a set of pneumatically controlled stilts that allow the wearer to increase their height significantly at the push of a button. We often see drywall contractors wearing stilts of a similar height, but haven’t seen any that are able to raise and lower the wearer at will. The team built the legs from scratch, machining almost every component (including the air pistons) from stock metal. After some controls were added and some testing was done, the team found that raising one foot at a time was the safer route, although both can be raised for a more impressive-looking demonstration that is likely to throw the wearer off balance.

The quality of this build and the polish of the final product are incredibly high. If you have your own machine shop at home this sort of project might be within your reach (pun intended). If all you have on hand is a welder, though, you might be able to put together one of [Make it Extreme]’s other famous builds: a beer gun.

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Simple Fuel Pressure Alarm Averts Diesel Disaster

If you could spend a couple of bucks on a simple project that might prevent a $2000 repair bill on your vehicle, you’d probably build it, right? That’s the idea behind this simple low-pressure alarm for a diesel fuel system, and it’s so simple it makes you wonder why the OEM didn’t do it.

We normally see [Bob Johnson] coming up with nifty projects (like this claw or this camera slider) that more often than not combine woodworking and electronics. But no tree carcasses were harmed in the making of this project. [Bob]’s goal is just to sound a warning and flash a light if the output of a pressure switch goes to ground. That indicates the lift pump in his Dodge Ram’s fuel tank has failed, which could lead to the sudden failure of the downstream injector pump for lack of lubrication by the fuel itself. His simple ATtiny85 circuit lives on a small perfboard in a 3D printed case and taps into a $30 fuel pressure switch. The microcontroller code enables a short delay to prevent nuisance alarms, and if the pressure drops below 5 PSI, [Bob] gets a chance to shut down the engine and disappoint his mechanic to the tune of $2000.

Maybe it’s planned obsolescence on the OEM’s part, or maybe it’s not. But kudos to [Bob] for a simple hack that averts a potentially expensive problem.

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Build Your Own Sensor Skin

Scientific research, especially in the area of robotics, often leverages cutting-edge technology. Labs filled with the latest measurement and fabrication gear are unleashed on the really tough problems, like how to simulate the exquisite sensing abilities of human skin. One lab doing work in this area has taken a different approach, though, by building multi-functional sensors arrays from paper.

A group from the King Abdullah University of Science and Technology in Saudi Arabia, led by [Muhammad M. Hussain], has published a fascinating paper that’s a tour de force of getting a lot done with nothing. Common household items, like Post-It notes, kitchen sponges, tissue paper, and tin foil, are used to form the basis of what they call “paper skin”. Fabrication techniques – scissors and tape – are ridiculously simple and accessible to anyone who made it through kindergarten.

They do turn to a Circuit Scribe pen for some of their sensors, but even this nod to high technology is well within their stated goal of making it possible for anyone to fabricate sensors at home. The paper goes into great detail about how the sensors are made, how they interact, and how they are interfaced. It’s worth a read to see what you can accomplish with scraps.

For another low-tech paper-based sensor, check out this capacitive touch sensor keyboard.

Thanks for the tip, [Mattias]

Running Calculus on an Arduino

It was Stardate 2267. A mysterious life form known as Redjac possessed the computer system of the USS Enterprise. Being well versed in both computer operations and mathematics, [Spock] instructed the computer to compute pi to the last digit. “…the value of pi is a transcendental figure without resolution” he would say. The task of computing pi presents to the computer an infinite process. The computer would have to work on the task forever, eventually forcing the Redjac out.

Calculus relies on infinite processes. And the Arduino is a (single thread) computer. So the idea of zeno_03running a calculus function on an Arduino presents a seemingly impossible scenario. In this article, we’re going to explore the idea of using derivative like techniques with a microcontroller. Let us be reminded that the derivative provides an instantaneous rate of change. Getting an instantaneous rate of change when the function is known is easy. However, when you’re working with a microcontroller and varying analog data without a known function, it’s not so easy. Our goal will be to get an average rate of change of the data. And since a microcontroller is many orders of magnitude faster than the rate of change of the incoming data, we can calculate the average rate of change over very small time intervals. Our work will be based on the fact that the average rate of change and instantaneous rate of change are the same over short time intervals.

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Retrotechtacular: Forces Acting On An Airfoil

floating film title We’ve probably all experimented with a very clear demonstration of the basic principles of lift: if you’re riding in a car and you put your flattened hand out the window at different angles, your hand will rise and fall like an airplane’s wing, or airfoil. This week’s Retrotechtacular explains exactly how flight is possible through the principles of lift and drag. It’s an Army training documentary from 1941 titled “Aerodynamics: Forces Acting on an Air Foil“.

What is an airfoil? Contextually speaking, it’s the shape of an airplane’s wing. In the face of pressure differences acting upon their surfaces, airfoils produce a useful aerodynamic reaction, such as the lift that makes flight possible. As the film explains, the ideas of lift and drag are measured against the yardstick of relative wind. The force of this wind on the airfoil changes according to the acute angle formed between the airfoil and the direction of the air flow acting upon it. As you may already know, lift is measured at right angles to the relative wind, and drag occurs parallel to it. Lift is opposed by the weight of the foil, and drag by tension.

wind tunnel testing

Airfoils come in several types of thicknesses and curvatures, and the film shows how a chord is derived from each shape. These chords are used to measure and describe the angle of attack in relation to the relative wind.

The forces that act upon an airfoil are measured in wind tunnels which provide straight and predictable airflow. A model airplane is supported by wires that lead to scales. These scales measure drag as well as front and rear lift.

In experimenting with angles of attack, lift and drag increase toward what is known as the stalling angle. After this point, lift decreases abruptly, and drag takes over. Lift and drag are proportional to the area of the wing, the relative wind velocity squared, and the air density. When a plane is in the air, drag is a retarding force that equals the thrust of the craft, or the propelling force.

monometer tubesAirfoil models are also unit tested in wind tunnels. They are built with small tubes running along many points of the foil that sit just under the surface. The tubes leave the model at a single point and are connected to a bank of manometer tubes. These tubes compare the pressures acting on the airfoil model to the reference point of atmospheric pressure. The different liquid levels in the manometer tubes give clear proof of the pressure values along the airfoil. These levels are photographed and mapped to a pressure curve. Now, a diagram can be made to show the positive and negative pressures relative to the angle of attack.

In closing, we are shown the effects of a dive on lift as an aircraft approaches and reaches terminal velocity, and that lift is attained again by pulling slowly out of the dive. Remember that the next time you fly your hand-plane out the window.

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Weather station graphs history on webpage


Kudos go out to [Jose] for his work getting so many different components to talk to each other in this Arduino weather station that using a Raspberry Pi to display the data online.

The components shown above make up the sensor package. There’s an Arduino with a custom shield that interfaces the barometric pressure sensor, real-time clock chip, a digital temperature sensor, and a humidity sensor. On top of that shield is an XBee shield that lets this push data back to the base station. [Jose] also rolled in an LCD character display and a few buttons so that the user may view weather data without heading to the web.

A Raspberry Pi board makes up the other half of the XBee pair. It harvests the incoming data from the radio module using a USB to Serial converter cable. You can see the data log on the webpage linked above. Just choose the “LIVE” menu option and click on “Daily” to get a better overview of humidity and pressure changes.

Force carbonating root beer with dry ice

[Paul] is sick and tired of his homemade root beer being flat. He analyzed the problem with his carbonation techniques and ended up with a method of force carbonating beverages using dry ice.

He starts of by discussing the various methods that are used to carbonate beverages. There’s the old yeast and sugar trick that takes place inside of a sealed bottle. But this takes time, and if you don’t calculate the mixture correctly you could have over or under carbonated bottles (or exploding bottles in the case of glass beer bottling). [Paul] himself has tried the dry ice in a cooler full of root beer method. The problem is that the cooler isn’t pressurized so the carbonation level is very low. You need to have cold temperatures, high pressure, and the presence of carbon dioxide all at the same time in order to achieve high levels of carbonation.

His solution is to use a 60 PSI safety valve. He drilled a hole in a plastic bottle cap to receive the valve. He then drops a few chunks of dry ice in and seals it up. The valve will automatically release the gas as the pressure builds past the 60 PSI mark. What he ends up with is a highly carbonated beverage in a matter of minutes.

If you don’t mind spending some cash you can use an adjustable pressure regulator. This way you can carbonate just about anything.

[Thanks Steven]