Accurately Measuring Electrical Conductivity

November 10, 2014 by Ethan Zonca 4 Comments

[Ryan] designed a PCB that lets you easily take readings from a commercial electrical conductivity probe over I2C. Conductivity measurements are great for measuring the salinity of a solution, which is useful for applications like hydroponics. While the probes themselves are a bit pricey (on the order of $50 from eBay), they are very accurate and last a long time.

Commercial conductivity probes contain platinum electrodes to prevent corrosion. The electrodes are excited with an AC signal, which prevents polarization of the solution and avoids chemical reactions at the electrodes. The voltage across the two electrodes is measured while the electrodes are being excited, which is proportional to the conductivity of the solution

[Ryan]’s board generates +/-5v and uses a Wien bridge oscillator to generate a sine wave which excites the outermost electrodes. The voltage across the electrodes is amplified and fed into a MCP3221, an inexpensive 12-bit ADC with an I2C interface. [Ryan] also wrote an Arduino library for the MCP3221 so you can easily get your probe up and running.

The Platinum Catalyst Use In A Vintage Lighter

November 1, 2014 by Mike Szczys 14 Comments

[Ben Krasnow] has an inimitable knack for choosing the most interesting concepts for his experiments. We’re sure it’s a combination of base knowledge and epic-curiosity. This time around he’s showing off a vintage cigarette lighter whose quirk is not needing to be “struck” to produce a flame. It’s a catalytic lighter that uses platinum to ignite methanol vapors.

The concept shown in the video below is platinum’s catalyst properties with some types of flammable gasses. The image above shows the cap of the lighter which includes a protective cage around a hunk of fine platinum powder known as platinum black. It is suspended by platinum wire and as the hydrogen passes by the reaction causes the platinum black and wire to glow red-hot.

This simple, quick experiment fills in our own knowledge gaps. We were already familiar with the role that catalytic converters play in automobiles; consuming any unburned hydrocarbons before they exit a vehicle’s exhaust system. We also know the these devices are targets for thieves seeking the platinum (and other metals like palladium and rhodium) found inside. Now we know exactly how catalytic converters work and the integral role that platinum plays in the process. All thanks to [Ben’s] demonstration of how this lighter works.

Now, if you wear a platinum wedding band and your hand passes a jet of hydrogen are you likely to get burned?

Continue reading “The Platinum Catalyst Use In A Vintage Lighter” →

Take Your Samples For A Spin With The RWXBioFuge

October 21, 2014 by Theodora Fabio 14 Comments

We have a confession to make: we love centrifuges. We’ve used all shapes and sizes, for spinning bags of whole blood into separate components to extracting DNA, and everything in between. Unfortunately, these lab staples are too expensive for many DIY-biologists unless they buy them used or build them themselves. [Pieter van Boheemen] was inspired by other DIY centrifuges and decided to make his own, which he named the RWXBioFuge.

[Pieter] designed the RWXBioFuge using Sketchup, OpenSCAD, and InkScape. It features a Thermaltake SMART M850W ATX power supply, an R/C helicopter Electronic Speed Controller (ESC), and brushless outrunner motor. For user output it utilizes a 16×2 LCD character display with an I2C interface.The frame is laser-cut from 3mm MDF while the 3D-printed PLA rotor was designed with OpenSCAD.

An Arduino handles the processing side of things. [Pieter] used an Arduino Ethernet – allowing a web interface to control the centrifuge’s settings and operation from a distance. We can see this being useful in testing out the centrifuge for any rotor/motor balance issues, especially since [Pieter] states that it can be configured to run >10,000 rpm. We wouldn’t want to be in the room if pieces start flying off any centrifuge at that speed! However, we feel that when everything’s said and done, you should have a centrifuge you can trust by your side when you’re at your lab bench.

While there are similarities to the Openfuge, the larger RWXBioFuge has rotor capacities of eight to twenty 1.5-2.0ml microcentrifuge tubes. Due to the power supply, it is not portable and a bit more expensive, but not incredibly so. There are some small touches about this centrifuge that we really like. The open lid detector is always a welcome safety feature. The “Short” button is very handy for quick 5-10 second spins.

A current version of the RWXBioFuge is being used at the Waag Society’s Open Wetlab. [Pieter’s] planned upgrades for the next version include a magnetic lid lock, different rotor sizes, an accelerometer to detect an improperly balanced rotor, and optimizing the power supply, ESC, and motor setup. You can never have enough centrifuges in a lab, and we are looking forward to seeing this project’s progress!

Check out a few more pictures of the RWXBioFuge after the break.

Continue reading “Take Your Samples For A Spin With The RWXBioFuge” →

Margarita Drip Infuser Ensures A Perfect Mix

October 14, 2014 by James Hobson 13 Comments

In order to get a margarita just right, the various ingredients need to be mixed together quite vigorously to over-come the different viscosity of the fluids. Looking to create his own barbot of sorts, [TVMiller] decided to make a Margarita Drip Infuser to help make margaritas a bit easier.

Using various chem lab supplies, [TVMiller] has cobbled together something pretty awesome. The Infuser can take up to 8 different ingredients into its test tube reserves, and after the drink ingredients are programmed on the computer, the magic begins.

An Arduino Uno controls a bank of 8 relays which control small fluid solenoids, with each control pulse releasing just a single droplet of fluid. An LED for each valve is run in parallel adding a bit of a light show to the mixing experience. If that’s not enough, he’s also created a copper cooling coil to chill the drink as it is poured.

Continue reading “Margarita Drip Infuser Ensures A Perfect Mix” →

DIY Magnetic Stirrer Looks Professional

September 18, 2014 by Rich Bremer 19 Comments

Stirrers are used in chemistry and biology labs to mix containers full of liquids. Magnetic stirrers are often preferred over the mechanical types because they are more sterile, easier to clean and have no external moving parts. Magnetic stirrers quickly rotate a magnet below the glass beaker containing the liquids that need mixing. The magnetic field travels effortlessly through the glass and reacts against a small magnetic cylinder called the stir bar. The spinning stir bar mixes the contents and is the only part of the mixer that touches the liquids.

[Malcolm] built his own magnetic stirrer. Unlike some DIY stirrers out on the ‘web, this one gets an “A” for aesthetics. It’s clean white lines allow it to look right at home in the professional laboratory. The graduated knob looks good and is functional too as the the potentiometer it is attached to allows multiple mixing speeds. Surprisingly, a D-size battery is all that is needed to power the stirrer. Most of the parts required for this project can be found in your spare parts bin. [Malcolm] has written some excellent instructions on how he made the stirrer including a parts list and schematics.

Want to make a magnetic stirrer but aren’t into chemistry or biology? No worries… I pity the fool who don’t build one of these….

The Science Of Strengthening Glass

August 10, 2014 by Rick Osgood 24 Comments

Strengthen Glass

[Ben Krasnow] is at it again. This time he’s explaining a simple method for strengthening glass. As usual, he does a fantastic job of first demonstrating and explaining the problem and then following it up with a solution.

[Ben] first uses a simple rig to place a controlled amount of force against a glass microscope slide. His experiment shows that the slide shatters once about 30psi of force has been applied to the center of the slide.

[Ben] then goes on to explain that current methods for producing glass leave many tiny impurities, or cracks, in the glass. As the glass slide flexes, the inside edge is placed into a compression force while the outside edge is under tension. The glass is more easily able to handle the compression force. The tension is where things start to break down. The tension force eventually causes those tiny impurities to spread, resulting in the shattering glass.

One possible solution to this problem is to find a way to fill in those tiny impurities. According to [Ben], most glass has sodium added to it in order to lower the melting temperature. [Ben] explains that if you could replace some of these smaller sodium atoms with larger atoms, you could essentially “fill” many of the tiny impurities in the glass.

[Ben] does this himself by heating up a small vat of potassium nitrate. Once the powder becomes molten, he submerges the glass slides in the solution for several hours. During this time, some of the sodium atoms are replaced by potassium atoms due to the natural process of diffusion.

Once the slides have cooled down, [Ben] demonstrates that they become much stronger. When placed in the testing rig, the stronger slides do not break until the pressure gets between 60psi and 70psi. That’s twice as strong as the original glass. All that extra strength from such a simple process. Be sure to watch the full video below. Continue reading “The Science Of Strengthening Glass” →

Connecting Inexpensive PH Probes With Ease

May 26, 2014 by Mike Szczys 11 Comments

[youtube=https://www.youtube.com/watch?v=yKigsN8046k&w=580]

We’ve mentioned that it’s hard to find someone not selling or crowd funding something at Maker Faire. Despite the fact that [Ryan Edwards] is selling his boards, we still got the feeling that he’s a hacker who is selling just to make sure the idea he had is available for other hackers to use. He showed us his interface boards for inexpensive pH probes.

Since we’re always looking for more chemistry hacks to run, it was nice to hear [Ryan’s] description on how these probes (which can be had for around $9 on eBay) actually work. It turns out it’s all about salt. When it comes to the electronics, the board provides a connector for the probe on one edge, and pins for voltage, ground, and I2C on another. Rig this up with your microcontroller of choice and you’ll be building your own automatic pool doser, fish tank minder, or one of a multitude of food-related hacks.

Head on over to Sparky’s Widgets to see a few other demo applications.