Take Your Samples for a Spin with the RWXBioFuge

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.

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[Charles’s] Epic “Total-Recap” GoKart Post

charlesEVPost

If you’ve built an electric vehicle in the past few years, you probably owe [Charles] a couple of beers. Now you can feel more indebted to him after you read his 17,500-word, 10-part post covering everything you need to know about electric go-kart design. You’ll want to grab a sandwich to keep you company.

You probably recall the Chibikart from posts earlier this summer, which is one of an endless list of EV projects [Charles] has up his sleeve. He’s been teaching MIT students how to build EV karts for a while now, and this total-recap “2.00gokart” novel is [Charles’s] way of sharing the wealth. This is more than a simple how-to guide, though. Instead, it reads like a teacher’s edition of GoKarting 101, with a few brief and important histories, walk-throughs of how the class evolved, exhaustive links to vendors, graphs, videos, and plenty of reference and documentation.

If you have even the slightest interest in electric vehicles, do yourself a favor and give it a browse. There are a couple of videos after the break, and if you need some more motivation, check out the EV skateboard that uses a lot of the same parts.

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OpenFuge: an open-source centrifuge

openFuge

Biohackers, fire up your laser cutters. [CopabX] has developed OpenFuge: a (relatively) low-cost, open-source centrifuge from powerful hobby electronic components. If you thought the VCR centrifuge wasn’t impressive, trolls be damned– OpenFuge can crank out 9000 RPM and claims it’s capable of an impressive 6000 G’s. [CopabX] also worked in adjustable speed and power, setting time durations, and an LCD to display live RPM and countdown stats.

And it’s portable. Four 18650 lithium cells plug into the back, making this centrifuge a truly unique little build. The muscle comes from a DC outrunner brushless motor similar to the ones that can blast you around on a skateboard but with one key difference; an emphasis on RPMs over torque. We’re not sure exactly which motor is pictured, but one suggestion on the bill of materials boasts a 6000 KV rating, and despite inevitable losses, that’s blazing fast at nearly 15V.

You’ll want to see the demonstration video after the break, but also make time to swing by Thingiverse for schematics and recommended parts.

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Rebuilding a fried fan motor

The fan motor on [Pete’s] oscillating tower fan conked out on him. It’s a shame to throw away the whole thing, but it’s near impossible to source parts for a small appliance like this one. So he set out to rebuilt the motor and get the thing working like new.

The motor in question is of the brushless AC variety. [Pete’s] gut told him that the failure was due to bad lubrication of the bearings at the factory. It stopped working because the commutator could no longer rotate freely. A check of the continuity of each of the coils led him to this thermal fuse. When the motor seized the AC current built up a lot of heat. This fuse is made to burn out before a fire can start but now it needs to be replaced. With a new one in place he reassembled the motor, making sure to pack the bearings with some quality lubricant. Now he’s once again ready for a long hot summer.

The trials of working with brushless DC motors for the first time.

We’ve all worked with DC motors at some point. Even if you aren’t a big hardware person, you’ve probably at least picked up a motor as a kid and touched a battery to the leads causing it to whir to life. These are usually standard DC motors and not their brushless relatives. Brushless motors require a bit more work since you are manually controlling things that are normally taken care of with the brushes. This article won’t teach you how, rather it will show you the mistakes one person made in his inaugural effort to use them. It is mildly amusing, but the project summary that he’s using them for seems even more interesting.

The job that’s been paying my bills and keeping me away from artsy-fartsy circuits for the past six months involves making a set of these enormous robot doors for a Certain Very Fancy Person’s house. Each door is 13 feet tall, around 7 feet wide, and weighs 1500 pounds. There are 66 of them in said house, and more in the servant quarters(!?!). The circuits on board each door have to handle running an onboard air compressor (which regulates a pneumatic weatherseal) as well as keeping track of temperature to linearize the pressure sensors when the weather gets cold. They also have to charge and maintain sealed lead acid batteries. They have commutated power rails. They have to communicate over said power rails, and do so using an capacitively-coupled data slicer and a proprietary protocol I wrote. This protocol has to be robust enough to bootload the processor over. It’s a proper embedded systems job.

Wow.

[via Adafruit]

Arduino Electronic Speed Control explained

You can salvage some nice motors out of optical drives but they can be tricky to control. That’s because brushless DC motors require carefully timed signals used in a process called Electronic Speed Control (ESC). [Fileark] built and ESC using an Arduino and has a couple of posts explaining the concept and demonstrating how it works. His test circuit uses six 2N2222 transistors to protect the Arduino from excessive current. You can see six red LEDs above which are inline with the base of teach transistor. This gives visual feedback when a transistor is switched, a big help for troubleshooting your circuit.

Once you’ve seen the videos after the break you’ll probably come to the conclusion that this is an impractical way to use a brushless motor. But it is a wonderful way to learn about, and experiment with the concept of ESC. Chances are you can get your hands on an old optical drive for free, making this an inexpensive weekend project.

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Build your own hub motor

Hub motors put the power inside of the wheel. [Teamtestbot] goes deep into the hows and whys of building these motors, from parts, to windings, to the math behind the power ratios. The working example puts an electric motor inside the rear wheel of a Razor scooter. Past projects used belts to transfer the work of the motor to the wheel of the scooter. By integrating the motor and the wheel you end up with a much cleaner looking product. Check out the motor testing and the scooter test drive after the break.

For more tips on building your own electric motors take a peek at the Fly Electric page we covered back in November.

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