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121  Topics / Robotics / Re: Angular position sensor? on: July 17, 2012, 10:31:28 am
If you have access to the end of the shaft you can mount a magnet and use a special Hell-effect angle encoder.

What you want is called an Absolute Shaft Encoder.
Well, the hall effect sensor requires rotation - it senses speed.
I do want an absolute shaft encoder, but not in the old style that uses a coded pattern on a disk. I wanted something using a more modern technology - something that sense changes in fractions of a degree, perhaps. Does such a device exist?
122  Using Arduino / Programming Questions / Re: Confused re C/C++, "Wiring" and "Process" langauges on: July 17, 2012, 10:24:41 am
Processing is based on Java, so is quite different to Wiring, which is based on C/C++.
That's not really helpful. Why would I use the Process or Wiring languages?
123  Using Arduino / Programming Questions / Confused re C/C++, "Wiring" and "Process" langauges on: July 16, 2012, 11:04:23 am
I know C/C++ very well. But I don't understand the purpose behind the Wiring and Process languages. I read info about them on the web, but I can't understand what they have that is very different from from C/C++. Can you someone summarize?
124  Topics / Robotics / Angular position sensor? on: July 16, 2012, 10:20:09 am
This is for several uses on a robot. I am looking for a sensor that provides a code for the angular position of a shaft - such as a steering shaft or a disk that rotates a camera mounted on it. The idea is to determine the angle when the shaft is NOT turning. This is not for detecting high-speed changes. What is available?

Years ago, this was done with a shaft encoder - a metal disk with printed patterns that passed under a light sensor as it rotated. The position coding was obviously not very accurate, and got worse as the disk got smaller in diameter. I would like something that is a bit more modern in technology. What's available?
125  Using Arduino / Installation & Troubleshooting / Re: What is a "shield"? on: January 09, 2012, 04:40:37 pm
"Shield" is the name given to anything that plugs in on top of the Arduino. 

Here's some examples:
Thank you. The pictures made the matter clear.
126  Using Arduino / Installation & Troubleshooting / Why Flash and EEPROM memory?? on: January 07, 2012, 02:19:07 pm
I noted that many Arduino boards have both EEPROM memory and Flash memory. I know the EEPROM is normally used for the static program while the RAM is used for volatile data. But I don't know what the flash memory is for?

Also the DUE (ATMEL SAM3U)( has no EEPROM at all. Why is that?
127  Using Arduino / Installation & Troubleshooting / Re: Tabular comparison of Arduino boards? on: January 07, 2012, 12:05:23 pm
That's the kind I wanted. I Googled it again and that link was well down the list. The link in that link goes to
That's a larger version of the spreadsheet at

Thanks very much.
128  Using Arduino / Installation & Troubleshooting / Tabular comparison of Arduino boards? on: January 06, 2012, 06:05:16 pm
I have seen web page listing Arduino boards and explaining a bit about their make-up. However, it would be great to see a tabular comparison that shows memory size, clock speed. etc. for each. Does such a web page exist?
129  Using Arduino / Installation & Troubleshooting / What is a "shield"? on: January 06, 2012, 06:02:01 pm
I have read over and looked at the pictures of all Arduino boards. Some are, however, marked as a "shield". What is meant by the term "shield" in this context? Are they for added components to be controlled by the main board - a substitute for, say, a solderless prototyping board? Are they to be "piggy-backed" on a main board - somehow plugging in on top?
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