Get your tweets in now, the Thermal Tweeter live stream will end later this week. Send a tweet to @dangerousproto and watch it print out live on the USTREAM feed.
The Thermal Tweeter is sitting in the photo studio, and we need it back to document a few new projects. Judging for the Adafruit Make It Tweet Challenge ends July 5th, and the live stream will come down shortly after
Last chance to print your tweets @dangerousproto – [Link]
Google just recently added voice search functionality to it’s Chrome browser and asked the folks over at Breakfast to come up with something to show off the new feature. [via]
The Verbalizer is an Open Source Bluetooth dev board that allows you to make a Voice Search device of your choosing. In the default configuration, touching the board starts a wireless Voice Search and prompts you to “speak now” to search. What I like is the fact that it is freely modifiable and includes downloads for the software/code, docs, schematics and laser cutter files. With all this information you can make one yourself. How awesome is that?
The Verbalizer – [Link]
Pulse-position modulation (PPM) is a signal modulation used for both analog and digital signal transmissions. This method is widely used for optical communication systems such as optic fiber and IR remote controls, where efficiency is required and little or no external interference occurs.
Pulse Position Modulation and Differential PPM – [Link]
Sometimes in the embedded system world we need to process the analog world and sending the signal to the microcontroller when the analog signal exceed some predetermine limit we’ve set. Some example of this situation is to send the interrupt signal to the microcontroller operation when the temperature is already exceeds certain limit or the light intensity exceeds certain bright level. This is when the comparator circuit becomes handy as it’s designed specially for this purpose.
Working with the Comparator Circuit – [Link]
If you’re interested in how delta-sigma modulators and ADCs work, you should check out this excellent introduction by Uwe Beis: [via]
When looking for an introduction to delta sigma conversion I found that most explanations were from a very theoretical point of view. It took me a while to understand how Delta Sigma converters really work. So I decided to write this introduction for people who prefer circuit diagrams to reading abstract equations.
To understand what I’m talking about you should at least be familiar with:
- Standard analogue techniques (op-amps, comparators etc.)
- Standard digital techniques (latches, binary codes etc.)
- Standard ADCs and DACs (resolution, speed)
- What a low pass filter is (at least an analogue one)
- The sampling theorem (sample frequency > 2 x input bandwidth, alias effects)
Delta sigma converters are different from other converters. Note that I do not make a difference between analogue-to-digital (ADC) and digital-to-analogue converters (DAC). Both are very similar and what is realized in one of them using analogue signal processing circuitry is implemented in the other one using digital signal processing and vice versa. I will explain the delta sigma technique with the analogue-to-analogue delta sigma converter as the first object.
An Introduction to Delta-Sigma Converters – [Link]
How do magnets work?… [via]
Questions that often come up are, “How do magnets work?”, or, “Why is iron magnetic?”, or, “What makes a magnet?”, or, “What is the magnetic field made of?”.
Those are good questions, and deserve a good answer. However, did you know that there is a lot about magnets at the atomic level that isn’t known yet? Just like with most of the other basic forces we are familiar with, such as gravity, electricity, mechanics and heat, scientists start by trying to understand how they work, what they do, are there any formulas that can be made to describe (and thus predict) their behavior so we can begin to control them, and so on.
The work always starts by simple observation (that’s the fancy word for playing around with the stuff!). That’s why it’s so important to have some “hands-on” experience with magnets. Have you taken two magnets and tried to push like poles together? How far away do you start to feel the repulsion? How does the force vary with the distance between them? When the magnets are moved off-axis to each other (moving them to the side and not head on) what does it feel like? Could you describe it like trying to push two tennis balls together? When you flip one around, what changes? What about moving one around the other in a circle? Try these things! That’s how you learn! Only when you play with (observe) them will you begin to understand how they work. This is the stuff great scientific pioneers did, like Faraday, Lenz, Gilbert, Henry and Fleming.
How do magnets work? – [Link]
Using the Bus Pirate to read the SVP supervisor power on password off an IBM T30 Thinkpad: [via]
A friend of mine recently came upon an old IBM T30 Thinkpad at an auction for $40. Bringing it home, he found that there was a power-on supervisor password. This can’t be reset by removing the battery, as the pswd is stored on an EEPROM on the motherboard….. So it came to me!
I recently purchased a Bus Pirate v3 from Seeedstudio, and decided to give it a quick test run..
IBM Thinkpad T30 Bios password reset with the Bus Pirate - [Link]
blog.makezine.com writes: [via]
When we last checked in on Ben Krasnow’s homemade SEM, he had just achieved his first successful image with the device. As his latest video shows, the project has come a long way since then. It’s a long clip, by internet standards, at almost 10 minutes, but Ben does a great job of communicating what he’s doing and why, taking us through each step in the imaging process, from loading the sample, through pumping down the vacuum chamber and powering up the electronics, to fine-tuning the image itself. Which looks great, by the way–even after making the trip to Maker Faire and back.
This is only the most recent in a series of truly outstanding projects from Ben. Check out the links below for some of our past coverage of his work, and Ben’s personal blog for new updates.
How-To: Operate a Homemade Scanning Electron Microscope – [Link]
Scott Harden writes:
Many RF oscillator designs involve a LC tank circuit. Creating a variable frequency oscillator (VFO) can be accomplished by varying the capacitance of inductance in the tank. Although capacitance is usually varied (think of the tuning knob on an AM/FM radio), variable capacitors are rare and expensive, and varicap diodes don’t offer a large tuning range at low voltages.
I stumbled upon a way to greatly improve the tuning range of an RF oscillator using a cheap variable inductor design. It’s essentially magnet wire wrapped a few dozen times around a McDonalds straw to form an air-core inductor, into which a screw can be driven in and out to variably disrupt the magnetic field! This is a good trick to keep in the back of your head because everyone who works with AC circuits, tank networks, or VFOs might need some extra frequency control, and this is a cheap and easy way to get it!
Screwy Oscillator Idea - [Link]