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View Full Version : Jon Williams- Feb. 2005 Nuts and Volts article.



Keith Hilton
02-16-2005, 01:52 AM
First-Thanks Jon, for writing the Stamp Applications in Nuts and Volts!· I could not agree more--Experimenting is where you learn.· I have read a lot of Tesla books, but the latest one I read, "Tesla Master Of Lightning" convinced me of one thing: Experimenting is where all things happen.· Now to Jon's article on the ADC0831 and ADC0832.· There is one other thing young people need besides experimenting, they need persistence!· With that said, I am determined to convert a small sensor voltage through an AD converter, through the Basic Stamp, and out to a digital pot.·In short, converting variable voltage to a variable·tracking· resistance. ·For example: Suppose you had a 500K potentiometer in a guitar volume pedal.· Suppose you did not want to use a potentiometer as the signal volume control.· You could get rid of the potentiometer by: Installing a sensor that read small changes in voltage, that fed to a AD0831, which fed to Basic Stamp, which controlled the DS1804, which controlled the resistance in the feedback loop of a inverting op amp arrangement.· I have done all this and it works, except for one minor problem.
Before we get to the minor problem, let me say the voltage sensors I used was a simple IR-LED that shined on a simple IR-photo transistor, with logrithmic shade taper.· By the way, I have a patent on controlling voltage with a particular type of shade using an IR-LED and IR-photo transistor which publishes Feb. 22, 2005.
Now, back to the minor problem that I mentioned.· If you have a guitar volume pedal that increases and decreases volume as the guitar player pushes up and down on the pedal, the DS1804 must track the increases and decreases, and output increases and decreases in resistance.· For this to work, pin 2 on the DS1804 must change quickly and follow the sensor voltage.· Pin 2 on the DS1804 is the up/down.· Yes, I can get the DS1804 to move up and down, but I can't come up with a program that makes it track the sensor voltage coming from the guitar volume pedal --IR-LED and IR-photo-transistor.· My biggest problem is understanding code for the Basic Stamp.· I don't mind experimenting-until the "cows come home", but I don't know enough about code to experiment in a productive way.· Even after taking a Basic Stamp class in College, and reading quite a few books.· If I can solve the up-down problem of pin 2 on the DS1804, then I will have a system that will track a sensor voltage and convert that information into a variable resistance that tracks the sensor voltage.· It all sounds complicated, but it is not.· I'm just a dumb·native·American·from the Ozark Mountains, and I have it all working except the pin 2 on the DS1804.· After reading Jon Williams article in this month's Nuts and Volts it seemed to me using the ADC0832, instead of the ADC0832 might be the solution to getting pin 2 on the digital pot-DS1802 to track. I don't··know enough code to get started experimenting. Helphttp://forums.parallax.com/images/smilies/smhair.gif

Jon Williams
02-16-2005, 02:02 AM
We have lots of information to get you up to speed so that your "experimenting until the cows come home" is indeed fruitful. Start with our "What's A Microcontroller" text, then move on to the others. We have a whole section of books on our web site, and those written by Parallax authors are available as a free download.

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Jon Williams
Applications Engineer, Parallax
Dallas, TX· USA