App Note: Adjustable power supply using a digital potentiometer

App Note: Adjustable power supply using a digital potentiometer:

How to use a digital potentiometer to calibrate and control an adjustable power supply.

A resistive feedback network is often used to set the output voltage of a power supply, since fixed resistors are simple to use and low cost. However, because a fixed network is not adjustable, the output voltage cannot be accurately set. Therefore, many power supplies use a mechanical potentiometer (pot) in the feedback network to set the output voltage. For easier automatic calibration, a mechanical potentiometer can be replaced with a digital potentiometer. Digital potentiometers are smaller, do not move significantly with age or vibration, and can even be recalibrated remotely. This application note explains some of the calculations required to use a digital potentiometer in this way and also provides a spreadsheet for easy calculations.

LogicCircuit

LogicCircuit:


John Tarbox found this open source software for designing and simulating logic circuits known as LogicCircuit. According to the developer’s website, “LogicCircuit is free, open source educational software for designing and simulating digital logic circuits. It has an intuitive graphical user interface allowing you to create unrestricted circuit hierarchy with multi-bit buses, debug circuits behavior with oscilloscope, and navigate running circuits hierarchy.”
This is a Windows project and requires Microsoft.NET Framework 4.0 or higher.
Visit the project’s official website for downloads and more information.
Via the contact form.

Touché with Arduino

Touché with Arduino:

Touché is a capacitive-sensing technology, developed by Walt Disney Research, which aims at providing touch and gesture sensitivity to a great variety of objects. From this research paper:

The technology is  scalable, i.e., the same sensor is equally effective for a pencil, a doorknob, a mobile phone or a table. Gesture recognition also scales with objects: a Touché enhanced doorknob can capture the configuration of fingers touching it, while a table can track the posture of the entire user.

The technique behind Touché is known as Swept Frequency Capacitive Sensing (SFCS): at a glance, by monitoring the capacitive response of an object over a specific range of frequencies (instead of a single one), it is possible to infer about its interaction with the outside world.

In his blog, Dzl describes his personal approach toward the development of a system capable to emulate Touché’s behavior with Arduino. Currently, the project is still in a early stage, but improvements and further developments are expected soon.

More information can be found here.

[Via: Geekphysical blog and Dzl's blog]

UPDATE 2012-06-02: you can now try out how to make it yourself following this instructable.

ASK AN EDUCATOR! – “How can I control a solenoid or motor with an H-Bridge?”

ASK AN EDUCATOR! – “How can I control a solenoid or motor with an H-Bridge?”:

Garrett asks:

how do i send/control the L293DNE motor driver to power a SOLENOID or just a dc motor

This is a really good question, and quite a popular topic. The L293D or DNE, depending on the manufacturer, is a Quadruple Half H-Driver or H-Bridge IC that allows for the control of high current loads from a low current source. The advantage of this chip over just using a transistor or MOSFET is in the fact that you can control the polarity of your motor when used as a full H-Driver.
If you are looking to just control a solenoid, I would recommend using a transistor. Specifically one that can handle the relatively high current loads like a TIP120 or equiv. This transistor with a base resistor will be able to drive ~1A from just about any microcontroller. This can also be used to drive your motor and I actually ran a post earlier which gives a much more in depth overview.
Regarding your L293D, below is a circuit diagram that illustrates 3 possible configurations for driving a motor. The one the left shows the IC being used as a full H-Bridge. The pins are configured as follows:

• Pin 1 (1/2 Enable) – Channel 1/2 enable HIGH = ON
• Pin 2 (1A) – Channel 1 logic control
• Pin 3 (1Y) – Motor Lead
• Pin 4 – GND
• Pin 5 – GND
• Pin 6 (2Y) – Motor Lead
• Pin 7 (2A) – Channel 2 logic control
• Pin 8 (Vcc2) – Motor Power Supply

To turn CW, make 1A HIGH and 2A LOW. To turn CCW, make 1A LOW and 2A HIGH.
The diagram on the top and bottom right show how you can control your motor in one direction. The top right diagram shows the motor being controlled on the HIGH side and the bottom right diagram shows the motor begin controlled on the LOW side. The control scheme is essentially the same as above, though you will only be controlling one of the logic control lines.
I hope this has helped to answer you question and clarify the use of the L293D!

Don’t forget, everyone is invited to ask a question!



Click here!

“Ask an Educator” questions are answered by Adam Kemp, a high school teacher who has been teaching courses in Energy Systems, Systems Engineering, Robotics and Prototyping since 2005.

“How to Start Making Your Own Electronics with Arduino and Other People’s Code”

“How to Start Making Your Own Electronics with Arduino and Other People’s Code”:

How to Start Making Your Own Electronics with Arduino and Other People’s Code via Jan.

The word Arduino may conjure up an image of a wide-mouthed geek huddled over a work table, but its simplicity makes it an entry-point into electronics for even the most electronically inept. We’ll outline the basics of the Arduino itself, what the crazy jumble of wires means, and then step through how to use other people’s code and schematics to build your first electronics project, no programming required.

Great starter guide on Lifehacker.

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Arduino Leonardo ATmega32u4 with headers. The latest addition to the Arduino family is here! The Arduino Leonardo is a microcontroller board based on the exciting USB-enabled ATmega32u4 (datasheet). This chip has about the same amount of flash, RAM and capability as the ATmega328 found in the UNO. It has 20 digital input/output pins (of which 7 can be used as PWM outputs and 12 as analog inputs), a 16 MHz crystal oscillator, a micro USB connection, a power jack, an ICSP header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started.
The Leonardo differs from all preceding boards in that the ATmega32u4 has built-in USB communication, eliminating the need for a secondary chip (such as an FTDI friend, FTDI cable or the USB/Serial converter on the UNO). On one hand this means that sketches on the Leo are a little bigger because it’s also handling USB interaction. On the other hand, it allows the Leonardo to appear to a connected computer as a mouse and/or keyboard, in addition to a virtual (CDC) serial / COM port. It also has other implications for the behavior of the board; these are detailed on the getting started page.
We’re very excited to have a small shipment of Leo’s in stock. Please note that this board is very new and so is best used by people with existing Arduino experience as there may be a bug that trips up beginners. It is probably not going to work with nearly any shields other than the proto shield. We haven’t gone through and tested it with all the Adafruit shields and don’t guarantee it will work until we’ve sat down and done a lot of testing and coding, so keep that in mind!
This board is only supported in the latest Arduino IDE 1.0.1 so you will also need to update the IDE.
In stock and shipping (please not we only have a few of these, but sign up to be notified when the next batch is in if we’re out of stock!).

Everything You Always Wanted to Know About Audio Electronics (But Were Afraid to Ask)

Everything You Always Wanted to Know About Audio Electronics (But Were Afraid to Ask):
Peterson Goodwyn over at diyrecordingequipment is preparing a podcast with seasoned EE Duncan Gray. He writes:

One of the biggest obstacles for entry into the DIY community is that most of us arrive here from a music, not electronics background. We’ve all been there: you’re planning your next DIY project and the documentation casually tells you to “bias the transistor.” In that moment, very few of us want to be the one to ask, “umm…. what’s biasing?”
Well, now is your chance to ask all of those audio electronics questions you never found the right moment to ask! On Saturday, 6/9/2012 I’m recording a podcast with a real live EE who has volunteered to answer your questions. Please post your questions in the comments section by Friday, 6/8 and we’ll try to answer as many of them as we can. No question is too “dumb,” or too complex to ask.
…
Duncan Gray is an EE with over 30 years experience in the field, including a stint as a Senior Hardware Design Engineer for Digidesign. His areas of expertise include both analog and digital hardware design, audio transformers, power systems, and scientific programming. Many thanks in advance to Duncan for volunteering his time and expertise!

If you’ve got a question about audio design, be sure to head over there and post it in the comments over there so that he can include it in the podcast.

32 Innovations That Will Change Your Tomorrow

32 Innovations That Will Change Your Tomorrow:

32 Innovations That Will Change Your Tomorrow – Interactive Feature – NYTimes.com.

OpenCV knows where you’re looking with eye tracking

OpenCV knows where you’re looking with eye tracking:

[John] has been working on a video-based eye tracking solution using OpenCV, and we’re loving the progress. [John]‘s pupil tracking software can tell anyone exactly where you’re looking and allows for free head movement.
The basic idea behind this build is simple; when looking straight ahead a pupil is perfectly circular. When an eye looks off to one side, a pupil looks more and more like an ellipse to a screen-mounted video camera. By measuring the dimensions of this ellipse, [John]‘s software can make a very good guess where the eye is looking. If you want the extremely technical breakdown, here’s an ACM paper going over the technique.
Like the EyeWriter project this build was based on, [John]‘s build uses IR LEDs around the edge of a monitor to increase the contrast between the pupil and the iris.
After the break are two videos showing the eyetracker in action. Watching [John]‘s project at work is a little creepy, but the good news is a proper eye tracking setup doesn’t require the user to stare at their eye.




Filed under: digital cameras hacks, Medical hacks

One Enormous Breadboard

One Enormous Breadboard:

[Franklyn] wrote in to tell us about the The Hack Factory Big Board project. The Twin Cities Maker group, a Minneapolis/St Paul based hackspace, set out to provide an education tool to help students make the leap from schematic diagrams to bread board connections.   Naturally their conclusion was to create a humungous 10x scale bread board.  The board features scaled up yet fully functional capacitors, resistors, a dip switch, and the jumbo-est LEDs we’ve seen in a long while.
Like its 0.1″ pitch counterpart, passive components can be thrown in 1″ pitch breadboard to create a myriad of analog circuits. The Twin Cities folks even tossed together an optical theremin using a scaled up photoresistor.  Beyond analog circuits the board can also demonstrate various ICs using either a custom breakout board featuring an 8-pin DIP socket or a vacuum formed Atmega 328 which boasts an internal Arduino Uno. The cool thing about the giant 28-pin DIP is that it does not necessarily function as a microcontroller.  Instead the UNO will be loaded with chip emulation programs geared towards the lesson at hand,  jumpers  select programs to teach debouncing, logic, flip-flops, and a whole slew of other basic concepts.
We are a bit concerned that the next logical step is a gigantic soldering iron,  but at least we finally have something to interface to the huge liquid crystal display.  If you still want more giant circuit stuff check out this 555 footstool.
Check out a quick intro video after the jump!



Filed under: arduino hacks

PCB manufacturing tutorial

PCB manufacturing tutorial:

There comes a time in every maker’s career where solderless breadboards won’t do, perfboard becomes annoying, and deadbug is impossible. The solution is to manufacture a PCB, but there’s a learning curve. After learning a few tricks from [Scott]‘s awesome DIY PCB guide, it’s easy to make your own printed circuit boards.
There are a few basic steps to making a PCB. First is designing the board in Eagle or KiCad. The next step, putting the design into copper, has a lot of techniques to choose from. Photo transfer, direct printing, and CNC milling have huge benefits, but by far the most common means hobbyists produce boards is with toner transfer using a laminator.
Unless you’re doing SMD-only circuits, a drill is required. Most people can get away with a Dremel or other rotary tool, but Hackaday has a favorite drill press that is perfect for drilling holes in FR-4. In part two of [Scott]‘s tutorial, he goes over solder masks, silk screens before jumping into vias. These small bits of copper conducting electricity through a circuit board are extremely hard for the garage-bound builder to achieve on their own, but there are a few solutions – copper rivets (anyone have a US source for these?) and copper foil can be used, but sometimes the most effective solution is just hitting the board with a lot of solder and heat.
Thanks [Upgrayd] for the title pic.

Filed under: how-to, tool hacks