Year: 2011

LaunchPad MIDI Synth

February 13, 2011 by 6 Comments

launchpad_midi_synth

[NatureTM] sent in a writeup for the MIDI synthesizer he recently built using a TI LaunchPad. The construction is pretty simple overall, consisting of little more than the MSP430, a handful of resistors, and an optoiosolater. Of course, a MIDI controller is required, but he already had that on hand.

Once the MIDI data is read from the optoisolator, his code takes care of the rest, adjusting the square wave sound generator to get the proper note. He does mention that since the synthesizer is monophonic, special care is taken to ensure that simultaneous notes are processed properly. You can route all of the sound into a single speaker, but he used the optoisolator to send the sound data to multiple LaunchPads instead, resulting in a fun little MIDI quintet.

He provides code and plenty of video on his site, but keep reading for a sneak peek of his synth in action.

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Flash Trigger With Programmable Delay

February 13, 2011 by 5 Comments

Here’s a flash trigger with a programmable delay. These triggers are often used to capture quick events like a balloon popping. The technique takes place in a dark room with the shutter open. When the event is triggered the flash illuminates the scene and an image is captured. Because these require precise timing it has typically been a chore to synchronize the event, hence solutions like using a pressure plate.

This build, which centers around a PICAXE 08M, allows the photographer to use any trigger they desire, but adds a delay. The box above shows the apparatus set up for a 42 millisecond delay. So if you’re using the sound of the balloon pop as a trigger, you can hold the flash off until the event really gets going.

[Thanks Two Part Epoxy]

NES Game Pad Guided Robotic Arm

February 13, 2011 by 11 Comments

nes_robotic_arm

Instructables user [Bruno] sent in his most recent creation, a robotic arm controlled using an old NES game pad. He scavenged the majority of his parts from a pair of old HP printers, including motors pulleys, belts and more. In fact, most of the metal and plastic components that he used come from the old printer chassis as well. He has included copies of the templates he used when manufacturing both the plastic and metal components, which should come in handy should anyone try to replicate his work.

[Bruno] also included all of the source code for the robotic arm and mentions that the project required two PICs due to pinout requirements. He ultimately decided to use two cheaper models over a single more expensive unit that would have supplied all of the pins he needed. His cost conscious build is impressive and undoubtedly demonstrates just how many old components can be reused in new projects if you really put some thought into it. Great job with this build, keep up the good work!

Be sure to keep reading to see some video of the arm in action.

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Modern Freaking: Pull Phone Numbers From YouTube Audio

February 13, 2011 by 48 Comments

[Charlie X-Ray] is having some modern fun with the phone system by pulling dialed numbers from the audio track of YouTube videos (translated). The first step was to find a video where a telephone is being dialed and the sounds of the keypresses are audible. You can’t tell those tones apart, but a computer can. That’s because each number pressed generates a combination of two out of seven closely related frequencies. [Charlie] isolated the audio using Audacity, then wrote a python script to generate a spectrogram like the one above. By matching up the two dark nodes you can establish which two frequencies were played and decode the phone number being dialed. So how does this work again… find audio of a phone being dialed, decode the number.. profit?

Uncrippling Lower Model Speakers

February 12, 2011 by 89 Comments

It looks like this low-end Sennheiser HD speaker has the same internals as it’s better-brother but has been altered to reduce sound quality. It’s not uncommon for manufacturers to hobble a product in order to sell more units at a lower price that reflects less features. Linksys WRT54G routers immediately come to mind, or perhaps the more recent Rigol 100 MHz oscilloscope hack is a better example.

In this case, that black piece of foam on the left has been added to the 555 version of the hardware to decrease the sound quality you get from the much more expensive 595 model. Take it out and you’ve got an upgrade that would have cost you more than a hundred bucks. Don’t think this is the only difference? There is a bit of a difference in case design, but [Mike Beauchamp] also found that if you acquire a replacement driver for either model you’ll get the same part.

Model Car Additions Make Us Hear Knight Rider Theme

February 12, 2011 by 5 Comments

This collection of model vehicle hacks adds obstacle avoidance in an attempt to make them autonomous. At the front end you’ll find two PCBs which use IR approximation to monitor the road ahead. We’re not familiar with this particular use of these IR receivers (TSOP1738) which we’re used to seeing in remote control receiver applications but if recent posts are any indication we think you’ll enjoy the use of a 555 timer on each of those boards.

The rest of the hardware is pretty common, a PIC 16F628 does the thinking while an L293D h-bridge drives the motors. Alas, we didn’t find a video, or even a description of the finished project. But there are full schematics, board layout pictures, and the code for both this vehicle and a second Tank version.

[Thanks Pieter]

SMS Controlled Irrigation

February 12, 2011 by 10 Comments

[Mhkabir] built an irrigation system that communicates by text message. The concept is simple, sending a text message to the system will cause it to switch on the water pump.

Many times we see text message manipulation via the Internet, or using a GSM module. But in this case an inexpensive cellphone is used as the communication interface. The vibration motor has been removed and those connections are monitored to signal incoming messages. Wire leads were soldered to the keypad contacts which allow an Arduino to send out text messages when there is a problem with watering. This isn’t an iron-clad system, as any incoming message will trigger the system and outgoing messages are limited to saved drafts. But a bit of creative programming and we’re sure more functionality could be squeezed out of this hardware.