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Fencer
04-19-2007, 04:53 AM
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I'm presently going to school at Pitt Community College in Greenville, NC and starting in the Electrical/Electronics class. I recently found out about "stamps" and would like to get some more info on what they are capable of working. I guess I'm trying to run before I can walk, but I know what I·need to learn to do what I·want . I have an·idea that I think they may be able to operate but need to find out if they are capable of doing what I need at a reasonable price.
·BTW, next year is when we get into PLC programming, but I need to get started now to try to get the idea I have completed. Any ideas on what would be a good starting point after reading what I want to do in the rest of this below?

····Here's what I need to do:

1) Using an O2 sensor with a 0-1 VAC output as the input signal·to the stamp.

2) Have the stamp give me a·Ground output to a 20 light·LED bar graph display.
···· Example: 1 LED = 0 V, 20 LEDs = 1 V 10-11 LEDs would be around .5 V

3) Use the same Ground output to supply the Base of a fast switching Transistor.

4) I'll install a set of DIP switches to select which output LED I want to power the transistors.

5)·The O2 reference voltage will be fast switching in the 1-2 Ms range, how fast· will a stamp operate?

Please bear with me, I know I'm in for a steep learning curve!··http://forums.parallax.com/images/smilies/smilewinkgrin.gif

I was going to try it with a LM3915 IC but found out it did not have a linear output.
Feel free to drop me a line!

Thank you, Floyd T. Moore
··············· Farmville, NC 27828
················ TheEquineFencer@AOL.com (mailto:TheEquineFencer@AOL.com)

Mike Green
04-19-2007, 05:10 AM
A Stamp would certainly work for this except for the shortage of I/O pins for the LED display. You could either use a Stamp with more pins (BS2p40) or use an I/O extender of some kind (like a 74HC595 ... Parallax has the part and the datasheet). A BS2p operates at about 10K instructions per second, the "plain" BS2 is slower, about 2K/second.

Go to the main Parallax page, select the Downloads menu item and start downloading and looking at the Stamps in Class tutorials and the Nuts and Volts columns. Both are chock full of the kind of information and examples you will need for this.

Depending on the details of the O2 sensor output, you may need an external analog to digital converter like the ADC08031 which is discussed in extensive detail in the tutorials.

Post Edited (Mike Green) : 4/18/2007 11:21:43 PM GMT

Fencer
04-19-2007, 06:36 PM
would you be interested in coaching me through this. My hope is to get good enough at things like this BEFORE we get into the PLC end of the classes so I standout and be recognised as the most outstanding one in the class, this will assist me in getting a job that pays as well as I was making working on Generators and switchgear before I got laid off from a corprate buyout. Thanks, Floyd.