Need help with Experiment 5 - LED Graph ( Dot or Bar ) - from StampWorks book.

HkySk8r187

Hello everyone. First time here on this forum, I just got the StampWorks Experiment Kit yesterday and this is the first time I have ever done anything like this so please excuse my ignorance.

I've been going through the experiments in the book that came with the kit. Here is the PDF for the book:
http://www.parallax.com/dl/docs/books/sw/Web-SW-v2.1.pdf

I got up to experiement #5 without any problems. I am a c++ programmer for a living so I'm not having a hard time understanding the code, it's the circuitry that I'm trying to learn as I go. I believe that I set up the breadboard and wires correctly but for some reason I don't get a reading from the Potentiometer, even though I set it up like the lesson says. I even tried using the source code that came on the CD instead of my own, thinking that maybe I had a type in the code I wrote. Still no luck. I'm having a hard time figuring out the problem because the book assumes you know basic circuits, and know how to read the circuit design images they give you.

I have pin0-7 wired to LED0-7. All LED connections are fine, I used them in the previous experiments.

I have my breadboard vss and vdd rails wired like the book said to do near the beginning.

I used a magnifying glass to figure out which of my capacitors was marked 104 ( that was trough enough on it's own haha )

I followed the 5 steps at the beginning of this experiment.

I even tried printing the result of the RCTIME command, it's always 0 no matter what the Potentiometer is dialed to.

Is there a step I'm missing in the wiring? Maybe something the circuit diagram indicates that the text/steps does not? I dont know how to read that diagram so I just follow the written steps with no luck.

The Professional Development Board has two potentiometers right? I see two of htem on the right side labeled "10k POT". Each has 6 pins, three rows of two.

Anyhow, hopeing to get some help from someone so I can keep working through this book. This is very interesting stuff, I can't wait to learn more. Thanks guys!

Chris Savage

If you can take a picture of your board that shows the wiring maybe we could identify a possible problem. Also, there are two potentiometers…do you get the same results from both?

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Chris Savage
Parallax Tech Support

HkySk8r187

I dont have a camera that I can get to right now, so instead I drew a picture of how it's laid out. I tried using both potentiometers and got the same results for both. Image is attached.

Chris Savage

Unless you made an error in your picture you have the potentiometer lead going to V_DD rather than V_SS as it should be. This could certainly be your problem. I hope this helps. Take care.

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Chris Savage
Parallax Tech Support

HkySk8r187

Oops, that is an error in the picture. The pot lead goes to the Vss ground rail on my actual board.

Chris Savage

What happens if you move the wire from P15 to P14 and adjust the code accordingly (to see if the I/O pin is damaged somehow)?

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Chris Savage
Parallax Tech Support

HkySk8r187

I will try that when I get home. The board is brand new out of the box so I was assuming everything was working. I'll post back here and let you know what happens with trying P14. Thanks for the good support.

HkySk8r187

Ok, I've taken the circuit apart and put it back together again from scratch and now it's working. I know I had the wiring right the first time but I must have had a bad connection somewhere. I'm very impressed with the level of support the company offers. Thank you very much! On to experiment #6 now!