Battery Pack Load

Submitted by paul on Tue, 2013-11-05 12:45

I purchased a cheap USB power pack, thinking it would be ideal for powering small projects.  But it automatically shuts off if the device isn't drawing a lot of power, since it's meant for charging cell phones.

Here's a 2 transistor circuit I built this morning that keeps it on with very little battery drain by using brief pulses.

Click "Read more" for the schematic, design details, and a PCB.....

Quality Audio on Teensy3 with Arduino

Submitted by paul on Mon, 2013-08-26 01:09

Over the last couple weeks I've been working on supporting quality audio (44.1 kHz, 16 bit) on Teensy3 using very simple Arduino style programming.  This weekend I added buttons and knobs to control parameters....

This work is still at an early stage.  I hope to publish a first alpha test version in about 1 month...

Edit: just a bit more info: The library manipulates audio with a collection of input, synthesis, processing and output objects that can be connected together in almost any way.  Audio connection objects automatically move the 16 bit data and run the synthesis and processing algorithms in the background, so the user's sketch isn't burdened with high bandwidth, real-time data manipulation.  The objects provide functions that can modify their behavior (volume, oscillator frequency, note on/off, modulation, etc) which can be used with extremely simple Arduino-style sketches, because the objects automatically handle all high speed data computation and movement in the background, triggered by interrupts and DMA transfers.

Designing a sytem to make excellent quality audio on Arduino with powerful features but also extremely easy has definitely turned out to be quite a challenge.  I'm still redesning the connection object's base class.  Much work remains, but now with I2S and PWM output working, .wav file playing and DDS sine wave generation all working, it really feels like it's starting to come together.  I hope to have the API stable enough (stable = unlikely to incompatibly change) for a first releast by October.

Serge, Subotnick, and Pure Data - programming sound for dance.

Submitted by jmej on Tue, 2013-08-20 13:40

This weekend I'm performing sound for a dance piece Light Noise that I've been working on for over a year. For the past year+ I've been refining a set of patches in Pure Data (PD) that I use to create conceptual sound and music for this piece.

I'm doing all of my sound generation, synthesis, and manipulation in realtime using PD and a midi controller. My PD patch outputs 4 channel sound, to 4 speakers I installed around the dance floor I built yesterday at Disjecta. I've attached a PD abstraction to this post.

Newbe - needs assistance in ordering

Submitted by Dan Phillips on Thu, 2013-08-01 05:12

I am looking for assistance (I will pay for your help) to design a Power distribution board for QuadCopters.  This is a two sided board with heavy copper due to the large load of up to 6 motors.

The board should be about 30mm in circumference with positive leads on one side and Negative leads on the other.  I am not sure if holes need to be drilled to aid in the soldering of 16ga wire.  I have a cad drawing I can email if you are willing to help.  I also would like the Power Distribution boards cut out of the sheet into 30mm disks.

Measuring microamps & milliamps at 3 MHz bandwidth

Submitted by paul on Sat, 2013-07-27 04:52

Recently I needed to actually "see" a current waveform in the 100 uA to 5 mA range with at least a couple MHz bandwidth.  This extremely expensive probe would have been perfect, but instead I built something similar for about $30 using the amazing Analog Devices AD8428 amplifier.

Click "Read more" for details and a scope screenshot....

DorkbotPDX 0x0C

  • When: Monday August 26th, 2013 - 8pm
  • WhereInstrument (map)
  • Who: All ages -- open to the public
  • Cost: Free!

Zach Archer

The Hypnolamp

Using LEDs and an Arduino, Zach converted a simple lamp into a hypnotic work of art. Knobs and sensors were added to control the animation and colors. Zach will reveal the HypnoLamp's secrets, and discuss the creative process, interactivity, and the coming revolution in home lighting.
Zach is a developer who focuses on interactive media and installations. He lives in Portland.

Drew McIntyre

The Art of Breaking Video: Observations, Insights & Instabilities.

Why stop at Speak n' Spells and Nintendos?  Big Pauper employees an obscure arsenal of hand-modified electronics to sculpt multimedia installations, sound design & glitch visuals.  Glitch video production will be the matter at hand this evening as Pauper shares the methods & the madness behind modifying video equipment, personal computers and video gaming hardware.  Should be good fun!!

Big Pauper is a multimedia artist, producer & mad scientist of sorts living here in Portland, OR.  He works as part of the circuit bent sound-art collective Folktek.  He also breaks video gear for a living under the enterprise Big Pauper Modified Circuitry.  He also just released a multimedia EP you should hear/view:


An open-mic session for those looking to show off a project, ask a question, solicit help, or incite collaboration.  Please limit to 5 minutes.


Ideal diode circuit fixing

Submitted by RussellSenior on Tue, 2013-07-16 02:01

At the bi-weekly meeting tonight, as promised, I brought my non-working circuit, and as promised, Paul helped me get it working.  It is a circuit that allows current to flow through a p-channel mosfet ( from a power supply to a 12V sealed lead-acid battery and a load (which draws about 120 mA, normally), but that prevents current from flowing from the battery back into the power supply.  The idea is to use an op-amp to compare the voltages upstream and downstream of the mo