Browser-based circuit simulator boasts a mountain of features

CircuitLab is an electronics simulator which you can run in a browser. Above you can see one of the example circuits provided to help show the power of the application. You can build your schematic (perhaps you want to try [Jeri's] psu shut-off timer?) in the editor mode, then switch over to the simulator to get data back from the components. In that mode, your cursor becomes a probe, and clicking on different parts of the circuit will return the calculated input and output voltages for that component. But wait, there’s more. It’s got time and frequency simulation in addition to the voltage simulator. This lets you look at waveforms fed through analog filters, or timing data like in the 555 timer circuit above.

Where does this fantastic tool come from? [Humberto Evans] and [Mike Robbins], the guys behind NerdKits developed this site. We’ve seen a lot of their hacks around here, like milling solenoids and making them play a xylophone. Check out the CircuitLab quick start video they put together after the break. [Read more...]

Halloween Hacks: Scaring small children with Huffman coding

The team over at NerdKits decided they needed to do something for Halloween. Only on Halloween is scaring small children is an admirable goal, so they demoed a way to play creepy sounds after a door has been opened.

To trigger the sound, a magnetic reed switch from an alarm system is attached to a front door. This triggers the microcontroller and with a bit of delay, some creepy audio can be played on a pair of speakers. The team decided to store all the audio data on the flash memory of their ATmega328p, but that wouldn’t allow for a very long scream. To extend the length of the wails of the damned, the NerdKits team decided to use Huffman coded audio.

Because Huffman coding relies on the most common value being assigned the shortest code, the team used a bit of Python and C magic to figure out the optimal encoding for their audio file. After the evil laugh was sufficiently compressed, the microcontroller was programmed to decode the audio and send it to a pair of speakers. The team made all the software for their project available here for your perusal.

Although this project could be thrown together in an hour with an Arduino and an MP3 shield, the NerdKits team wants to get kids to learn how things work, also an admirable goal. [Humberto] from NerdKits put a video up explaining the theory of the project. Check it out after the break.

[Read more...]

Lathe modification

The folks over at NerdKits got a shiny new Smithy 1220xl lathe/ mill. They found, however that adjusting the Z axis wasn’t as accurate as they desired. They decided to resolve this by installing a digital caliper and an LCD interface to display the adjustments. The writeup is quite detailed and the results seem to work great.

Modular systems using SPI

[Humberto] is at it again with a NerdKits video detailing the use of an SPI bus to communicate between microcontrollers. He started with a previous LED marquee project which was limited to a 5×24 LED Matrix and developed a modular solution to increase the size limitation.

The writeup and video embedded after the break do a great job of detailing the important differences between a stand-alone and a modular system. The good news is that the ATmega168 chips being used have a built-in interrupt based SPI protocol. Once wired correctly, a master control chip addresses each module separately, adding data to their buffer until a full frame has been transferred, then moves onto the next module.

Some of the caveats to this system such as digital transmission over long distances are discussed. We do wonder about power limitations if all LED’s in the marquee are illuminated at once. But that concern aside, if you’re thinking of playing around with an LED display don’t forget that there’s usually a huge price break for orders of 500 or 1000 LEDs!

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Motors and Microcontrollers 101

[Humberto] from NerdKits sends in the newest addition to their excellent collection of videos. This video goes over the basics of DC motor control with microcontrollers. They begin by showing nine experiments and observations that can be done by the average hacker with a multimeter, motor, LED, and jumperwire. Using the results from these they show how to model and calculate the properties of a motor. Lastly, it shows how to control a motor using PWM. They have supplemental text and demonstration code for an ATmega168 on their website.

Meat thermometer using predictive filtering

meatthermoafteradjustment

The guys over at NerdKits put together a really informative video on a meat thermometer using predictive filtering which is viewable below. The video, supplemental text, and code is available on their website. The thermometer is constructed of a LM34 temperature sensor attached to a piece of 12 gauge solid copper wire. The thermometer signal is processed on an ATmega168 microcontroller and visualized using the pygame library for python. The real gem in this project is their excellent explanation of predictive filtering, which could easily be utilized for a large number of projects.

[Read more...]

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