ARduino ground problems

I was receiving some very weird noise from the arduino that would come through in my servo. Turns out to be two problems:

1) I was running ground between arduino and the breadboard - but also supplying power to the breadboard and arduino from same external source. This resulted in problems both with the servo, and in the mouse pad of my mac mini! It was basically interference from the AC power strip.

2) The software that was running the servo was causing problems, I switched libraries.

Arduino MUX

Using the MUX board with Arduino is pretty great - I'm using it to read 16 different photoresistors. AFter running power, make sure to send ground signal to the EN as well.

Then 4 digital lines go to control the MUX, and one Analog in to read it.

Photoresistor

We are going to have photoresistors embedded in blocks that are wedged inside of wood panels on the bench, so I ran a test today on the photoresistor to make sure it worked.

The photo resistor is a relatively simple set up. The secret is to always detect for variance, and not to depend upon any specific light reading. I will have to have arduino run a series of callibrations when it starts, and then do it over the course of the day to account for fluxuations.

I will also have to have what I will call the ASS ALGORITHM. This is a proprietary algorithm to determine if there is an ass on the bench, or if it is just a poorly performing sensor. This will necessitate determining the range of asses out there. Such is work.

For a good and simple arduino example of photoresistor - check this out. Just remember that if you aren't using Arduino to power the photoresistor you have to connect your grounds.
http://www.arduino.cc/playground/Learning/PhotoResistor

xbee working

Thanks to this tutorial:
http://arduino.cc/en/Guide/ArduinoXbeeShield

Using the Arduino XBee Shields were easier than I thought. I set up wireless dual channel communication through a wall - approx. 90 feet apart.

It looks like the XBee are programmed out of box to receive all communications, and that one must program them to receive on a particular channel. Since the communication structures for this will not be very difficult, and I'll be writing my own protocol - that should suffice.

Now to buy that third Xbee and see if I can get all 3 chatting together!

Metal Detector with Arduino

I have hacked the metal detector to be able to have arduino receive and respond to any metal.

Using a $50 Bounty Hunter metal detector, I am took off the backing, and connect to the input and output on the VU meter. I then run this through a voltage divider, and send the output to the Arduino Analog In.

Being very new (noob) to electrical engineering, one aspect that caught me up is that I must connect the ground of the arduino to the ground of the power source (VU meter on the metal detector.) See the below image for circuitry.



Arduino is doing a great job notifying me of how much metal has passed by. Now to find some gold.

Multiplexer part deux

Today I attempted to hook the 4051 BE up with the arduino. I was a bit confused by how I should run ground since it appears, according to the tutorials I have found pins 6,7, & 8 all are connected to ground.

Currently, I can get voltage to surge when I connect power to an input, but it appears across some of the proximate inputs, rather than on a specific point. I obviously need a clean input since I will be using this with photoresistors.

4051 Chip as Demultiplexer

Spent today trying to use arduino to control a series of LEDs through a CD4051BE multiplexer/demultiplexer.

Referred to a series of tutorials on the chip, but it appears that all successful ones are for multiplexer (reading in) rather than demultiplexer.

I am planning on using these chips to read about 32 photosensors. I started out trying to do the demultiplexer with LEDs because there is a voltage input required, and I wasn't sure if the photoresistors will send it through. Therefore, I thought building with LEDs would be a good first step.

Unfortunately, I was unable to get the demultiplexer to output on a single channel. As arduino parses through the 8 combinations of 3 bits, the LEDs light up a variable amount. I appears that there is always a voltage going through, and the amount of voltage is dependent on the chip.

Potential problems are
1) I am not wiring this correctly
2) I am sending bits incorrectly in the arduino code
3) 4051 is not a good chip to use for demultiplexing.

iPhone blogging test

Bench Study

go to my flickr set page to see comments on each designs.

Arduino Bluetooth

Getting communication with Arduino bluetooth is definitely trickier than your average microcontroller - but considering all the leg work usually involved in bluetooth applications, it is a great addition. Here are the steps I figured out after about 3 hours of trying.

1) http://www.arduino.cc/en/Main/ArduinoBoardBluetooth has the basic info, but not really a user friendly instruction IMO

2) Set up your bluetooth with arduino before you open the arduino programming environment
--the passcode is '12345'

3) Open arduino and set the serial connection to 115200

4) put the following in your set up code:
Serial.begin(115200);

5) restart the arduino on each load. This is what got me. You have to hold down the restart button for about 15 seconds and then hit upload immediately.

NITs

Getting a monitor that can work in daylight means finding one that emits enough light. LCD monitors measure light in 'nits', which is roughly the amount of light traveling in one direction.

Monitors typically have around 300 nits. For our project we are going to need to have our display readable in full daylight. This means around 1.5 K nits.

Mechanism Research Resources

ITP Mechanisms and Things That Move class site by Dustyn Roberts
Resources

1-14-09 Meeting Notes

To do list:

1. JooYoun - Diagrams of other bench motor options
2. David - Test metal detector and document and post to blog
3. Begin scripting user scripts for the furniture
4. Email Eyebeam about possibility of Wizard of Oz