Beginner Project: Super Cheap Magnetic Mixer

March 16, 2011 by Jesse Congdon 23 Comments

[wesdoestuff]’s mother needed a clean way to mix together fragrance oils. Being the stand up kinda guy he is, [Wes] threw together a few spare parts to make this Magnetic Stir Plate.

The whole setup is amazingly simple. Pry the fins off of an old computer fan, glue a couple magnets to the fan’s hub. Drill a hole for a DC connector, find some sort of cover and.. Bob’s your uncle! [Wes] advises that you test the spacing of the magnets on the hub before gluing them permanently, as they can be a bit tricky to align.

The stir bar for non food items is a magnet bar from one of those crazy magnet and ball bearing toys, it is basically just a solid magnet covered in plastic. Food safe bars can be acquired, though they are not as cheap. With all that room under the hood we would love to see him throw in some kind of a PWM speed control but that could be a bit complicated. Most of us could throw this together from spare parts. Video after the jump!

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USB Man-in-the-middle Adapter

March 16, 2011 by Mike Szczys 21 Comments

The module works as a pass through, providing access to data and power lines for a USB device. [BadWolf] built it in order to sniff out communications between peripherals and the Universal Serial Bus. For now it just provides access to the different signals, but we think there’s quite a bit of usefulness in that. First off, the power rail is mapped out to a jumper, making it dead simple to monitor the voltage stability or patch in a multimeter to get feedback on current consumption. But you can also see in the foreground that a pin socket makes it easy to tap into the board using jumper wires. We think it would be a great breadboard adapter for USB work that would continue being useful after you’ve populated your first PCB for the prototype.

[BadWolf] has other plans in store for it though. He wants to intercept and decipher the communications happening on the data lines. In the video after the break he mentions the possibility of using a Bus Pirate for this (we have our doubts about that) but plans to start his testing with an STM32 discovery kit. We can’t wait to see what he comes up with.

DsPIC-based Spectrum Analyzer

March 16, 2011 by Mike Nathan 6 Comments

spectrum_analyzer

[Debraj] wrote to us describing a project he recently completed – a simple, compact spectrum analyzer using a 16-bit dsPIC microcontroller.

The analyzer is fed an analog signal, which is passed through a large resistor followed by an opamp. A DC offset is then applied to the signal, after which it is passed through a software-programmable gain amplifier before being fed into the dsPIC’s analog input. A Fast Fourier Transform calculation is done using code provided by the PIC’s manufacturer once 128 samples have been collected. The results are then displayed on the attached LCD in real-time.

If you get a chance, take a look at the video embedded below for a walkthrough and demonstration of his analyzer. [Debraj] says that the analyzer was built to measure harmonics in his home power lines, but for demonstration purposes, he has used a simple function generator instead.

If you’re interested in seeing some other spectrum analyzers, be sure to check out these items we featured in the past.

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Battery Capacity Tester Lifts The Veil On Manufacturer Capacity Claims

March 14, 2011 by Mike Nathan 24 Comments

battery_cap_tester

[Nick] was tasked with building a battery capacity tester by one of his teachers in order to test some aftermarket batteries that were purchased for their Vex robotics lab. The batteries were cheaper than the official version, but boasted more than twice the capacity. Fairly skeptical of the rating, he got to work designing his circuit.

He originally planned on discharging the battery through a resistor and measuring the voltage with a PIC microcontroller. After prototyping the circuit, he found that the PIC did not have enough storage space for the data he was collecting, and that there were issues with fluctuating current as the voltage decreased.

Undeterred, he built a new tester using a Teensy microcontroller and a different discharging circuit using a LM317T. This second version not only included an LCD screen to track the discharging process in real-time, but it also dumps all of the data and calculations to a spreadsheet on the computer connected to the Teensy.

The capacity tester works pretty well, according to [Nick]. He says that most batteries overestimate their capacity, and that his meter is getting readings within an acceptable variance when testing known good batteries. What about those knock-off batteries from China? He discovered that they can hold about half the charge that they claim – it’s a good thing he decided to test them out!

While he provides the software he used for the tester, there are no schematics to be found. Check out some of the other battery capacity testers we have featured in the past for tips on building one yourself.

DIY Hot Air Reflow Station

March 10, 2011 by Mike Szczys 10 Comments

Add to you bench tools by building this hot air reflow station. [Tobi] had a difficult time and was getting frustrated with the reflow oven he was building. He ditched that and set out on this project after drawing inspiration from a hot-air pencil project.

Pictured above is the business end of the device. On the right you can see the tubing that delivers air from an aquarium pump. At the center of the probe is a glass tube containing the heating element. A thermocouple is monitored by an ATmega644 to maintain the desired air temperature which can be dialed in on the base unit. This thing can put out air that’s around 500 degrees Celsius which has cause some problems with melted tubing and singed spacers. The final design includes a cover that fits over everything and hopefully provides adequate thermal isolation for the user’s hand.

[Tobi’s] base unit include faceplates for the front and back milled out of copper clad board. This really makes the tool look a bit more trustworthy. He assures us that there is a demonstration video on the way.

PC Casemod-inspired Benchtop PSU

March 9, 2011 by Mike Nathan 28 Comments

benchtop_psu

[Will] had a cheap power supply sitting around, and decided to turn it into a full-featured benchtop PSU. Inspired by some of the other benchtop supplies we have featured in the past, he decided that he wanted his PSU to be more than just a simple-looking box sitting on his work bench. Taking some cues from PC case modding, he put together a unit that is not only very useful, but also quite sharp looking.

The frame of the case was crafted from aluminum angle, while all of the other flat surfaces were made using black polycarbonate. He installed the standard 12v, 3.3v, and 5v terminals you would expect from any benchtop PSU, complete with an LCD display showing the voltages provided by each rail as measured by an Arduino stationed inside the case. Additionally, he installed a variable terminal capable of providing 1.3v-30v, along with its own LCD display. The most unique feature is the multimeter embedded in the front of the case, which makes it virtually impossible to lose.

The case is finished off as you might expect, if you have seen any of his previous work. It features LED lighting on the inside, large fans on either side of the case for optimal air flow, and a pair of machined aluminum handles.

Be sure to check out the quick video below of the PSU being powered on.

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Arduino Thermo-cam

March 9, 2011 by Kevin Dady 31 Comments

[Maxbot] wanted a inferared themo-cam that he could use to scan an area and display the results on his computer, the result is this Cheap-Thermocam. This little device is a inexpensive thermal sensor mounted on a pair of servo’s for XY scanning, custom java software and an Arudino to mate the two.

The sanner does a limited but still useful resolution of 42×32 pixels. To help out with smoothness of the colors, every other line of the finished product is interpolated against its neighbors. It takes the device about two minutes to measure each of the 1344 points, but what it lacks in speed it more than makes up for in cost, boasting around 100$ build cost, and ease of construction.

While exact details of what parts you need and how to hook everything up is lacking at this moment, there is a page in the works that will let you know all the good details “soon”, though if you are inspired to replicate one of these nifty devices it seems the most difficult part would be tapping into the sensor’s electronics and the custom software.

Cheap, hacky, and even comes with its own roll of duct tape. We have a short video for you after the break.

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