Regulator

I picked up an Analog Devices ADP3338 regulator to power the MP3 player. I am using one with Vin up to 8V, and Vout is 1.8V.

Speed and Detection

I'm enamored with the use of the ultrasonic range sensor for Blame. It currently gives me a very solid indication of anything within 5 feet. The active IR sensors can theoretically detect up to 5 feet, but they really get noisy out beyond 4 feet.

For Look, Scott and I chose passive IR motion sensors because we wanted a larger range, plus Look moves its eyes at motion now, rather than just detection of someone.

For Sycophant, ultrasonic range sensors would have been bad because of 1) clicking noise 2) inter-sensor interference and 3) latency (the ultrasonic sensors need about 0.3 second to get a good reading). Sycophant needs to move down the track really fast when it detects someone, and it is continuously talking.

For Blame, ultrasound works because 1) the clicking is kind of cool and creepy 2) I can turn the sensor off when the work is talking and 3) people might not get too close to the swinging arm, so a long distance is needed and 4) if people crowd around it, the long distance of sensing is less of a problem because it can accuse anyone in the crowd, then move to someone else.

On PWM, currently I am using the 1:4 prescalar on TMR0, with a 4khz internal clock. The on period of the PWM begins at 0xC0. This moves the arm a little fast, but moving the on period to begin at 0xD0 makes the arm a bit weak. I might have to re-jigger the prescalar to 1:2 then drop the on period length to get a solid yet slower movement.

Ultrasonic Proximity Detectors

A while back I picked up some ultrasonic proximity detectors from BG Micro (they don't seem to have them any more). They appear to be called "Mini-S Sensors", and have one output that detects at 7 feet, and one that detects at 5 feet.

More info on them is here.

Blame progress is coming around nicely. I have a nice steel superstructure now. I picked up some 4066 Quad Switches to control the button switches MP3 player (the strategy appears to work, hurrah!). And am painting the arm of Blame to get a nice image for the gallery postcard.

Arcade Electronics

So where do you go when you need a DB25 IDC connector right away? Arcade Electronics, which is just north of Springfield. Lots of good electronics, reasonable prices, no shipping if you just show up and buy it.

I stopped by Scott Hutchison's studio last night. We are evaluating whether we like the behavior of Look better with active IR sensors or passive IR (PIR)sensors. The jury is still out.

PIR sensors for home security systems generally operate like a relay. If there is "no intruder," they are either "normally open" circuit or "normally closed" circuit.

I'm always scared of blowing out PC parallel ports, so instead of using potentially hazardous voltage pull-ups and pull-downs to detect whether relays are open or closed, I hook the relay between a parallel port output and an input. I then drive the output up and down a few times. If the input pin follows the output pin every time, you know the relay is closed. Otherwise, it is open.

January show at Fraser Bethesda

I will take part in the "Art and Technology" group show at Fraser Gallery, Bethesda. Here are the details:

JANUARY 2006 - ART AND TECHNOLOGY
January 13 - February 8, 2006
Opening Reception - Friday, January 13 from 6pm - 9pm.

Other folks in the show include Scott Hutchison (who just got written up in a DC Magazine article), Claire Watkins (who does some really cool organic/technologic kinetic sculptures), David Page (who makes interesting "apparatus" that is sometimes fetish related).

"Blame" Swings

Sorry for the low quality, but here is the Canon SD400 with a Quicktime movie of the test rig for Blame.

I am using Radio Shack magnetic reed switches which can operate with a gap of up to 1 inch between the magnet and the switch. I think the arm is swinging too fast, I'll have to turn down the PWM duty cycle.

"Blame" hand

As an early birthday present, I got a Canon SD400. A very nice little camera!

Here is a picture of the hand of Blame:



It came out pretty good, except for that little "zit" on the top, which I have since filled in with a little bit of stone. I attached the hand to a CPVC slip end cover using a masonry screw and a big gob of Loctite Epoxy Gel (which is supposed to work with plastics and ceramics). Later, I epoxied the CPVC slip end cover to the "arm" CPVC pipe.

I have found a great site for "random" stuff like motors, power supplies, and PIR detectors: MPJA.com.

Finally, the work I am doing with Scott Hutchison, now named Look, got mentioned at DCist.