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11956  Forum 2005-2010 (read only) / Syntax & Programs / User type question on: November 21, 2008, 04:03:06 pm
Hi Group;

 I'm pretty new here and have only had my Arduino (Freeduino Serial v2.0 board kit) for a week now. My past experience with MP was with the Picaxe series for around a year or so. While I found the Picaxe to be a very good and affordable introduction, I wanted to venture into the C world. I have an extensive electronic  background in the process control industry but have been weak on software experience. Now that I'm retired I have the time to pursue this ambition.

Looking for a first good project (after testing with Blink of course  smiley-wink) I stumbled across a really cool open source PC monitoring, trending and data storage application called Liberlab.
http://www.liberlab.net/
There are some nice web casts included showing it's features and operations. I then found a site where a Arduino sketch had been developed to act as the data  front end for Liberlab.
http://www.uchobby.com/index.php/2008/01/19/arduino-liberlab-liberino/
I had to modify one function to get the digital read-back status to work correctly and found that the Liberlab data capture speed had to be set to at least  .02 seconds or more to operate reliably. It's working great, reading and displaying 4 analog inputs and controlling 6 digital outputs on the Arduino at 57600 baud rate.

Anyway the main reason I'm posting is I have a question about a type definition used in the sketch that I can't seem to find out it's source. Here are two examples from the sketch:

uint8_t status = readDigital8();

uint8_t ch = Serial.read();

There is no prior definition for "uint8_t" in the sketch and I didn't see it as a reserved word in the Auduino reference material. Is it buried in some standard library? The sketch of course compiles fine and the program works, but I haven't a clue where this type comes from. Can someone educate me in this?

Thanks
Lefty

11957  Forum 2005-2010 (read only) / Interfacing / Re: Reef Pico LED intefacing, 3 watt LED's and RTC on: January 21, 2011, 09:39:48 pm
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8:00AM = start fading first chain of led's in
8.30AM =  start fading in second chain of led's in
8.00PM = start fading second (first?) chain of led's out
8.30PM = start fading second chain of leds out.

Sounds like an interesting project. I'll just give a few little basic timing values to maybe get you started. Having a RTC makes it a pretty simple task I think. I will assume you will be using the analogWrite() function to PWM your led brightness.

 As the analogWrite() function only has a 0-255 step capacity for dimming of 0-100% brightness, and you wish to fade up or down over a 12 hour period, that means incrementing or decrementing the PWM value every 3 mins, that is close enough I think,  (3X256) / 60 = 12.8 hours cycle.

So your sketch needs to keep reading the RTC until it sees a 'start' time and then starts a pwm analogWrite command starting with 0 and incrementing the pwm value every three mins as read from the RTC. You can have o two time frames  going if you wished to have some overlap time between the two light assemblies, other wise it's just keep reading the RTC and see when it's time to make a move.

Lefty

11958  Forum 2005-2010 (read only) / Interfacing / Re: multiple arduinos, separate Processing scripts on: January 19, 2011, 11:25:43 pm
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Not good... ("Don't cross the streams!" I keep hearing...)

Good one.  ;D

I don't speak Processing, but I'm pretty sure some processing ghost buster may show up to help. Offer them a cookie.

Lefty
11959  Forum 2005-2010 (read only) / Interfacing / Re: Experiences with brushless DC pumps and PWM? on: January 18, 2011, 01:13:55 pm
 
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Are there any brushless DC motors in production, which would somehow get their coil-switching messed up by the frequent PWM power outages?
Anyway, anyone has this kind of thing running just fine, please let me know...

Most modern brushless DC motors most commonly utilize a ESC (electronic speed controller) that interfaces to a arduino as a simple servo controlled motor. The esc handles all the 3 phase switching requirements.

Standard two wire PM DC motors are often controlled with simple PWM control through a single transistor, or more complex H-drive circuit if forward/reverse rotatation is also required. How a given motor/pump will operate with PWM is hard to say, as torque Vs rpm Vs flow rate can be very non-linear and losses and friction and headpressure can require a non zero starting value for the pwm value range that can be utilized.

Lefty
11960  Forum 2005-2010 (read only) / Interfacing / Re: Need help in arduino RFID code on: January 15, 2011, 07:47:51 pm
I saw that too, but still can't figure out how the code is going to check with him? If a message is displayed in the forest with nobody around, was there really a message sent?


Lefty
11961  Forum 2005-2010 (read only) / Interfacing / Re: Need help in arduino RFID code on: January 15, 2011, 04:04:36 pm
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What is a gobi aloo sag?

Illegal alien? What...well it is a security application.  ;D

Lefty
11962  Forum 2005-2010 (read only) / Interfacing / Re: server based IDE on: January 13, 2011, 03:30:44 pm
Don't make me start throwing lighting bolts around.  ;D

Lefty
11963  Forum 2005-2010 (read only) / Interfacing / Re: server based IDE on: January 13, 2011, 02:27:07 pm
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DOWNLOAD:

to transfer (software, data, character sets, etc.) from a distant to a nearby computer, from a larger to a smaller computer, or from a computer to a peripheral device.

So the Arduino team had another brain fart when they decided to call moving a sketch from a larger computer (the PC) to a smaller computer (arduino) a upload operation.

Lefty
11964  Forum 2005-2010 (read only) / Interfacing / Re: server based IDE on: January 12, 2011, 03:11:53 pm
I just prey that the Arduino folks never add the function to read the value of the boards eeprom data and "download" it to the IDE. That would have to be explained more often then why to use resistors with leds.  smiley-wink

Lefty
11965  Forum 2005-2010 (read only) / Interfacing / Re: server based IDE on: January 12, 2011, 02:31:31 pm
It would add a whole new meaning (and means) to "upload a sketch" to my board.  ;D

Does anyone know why we say download a file from the web, but arduino is said to upload a sketch to the board? Or is life just funny that way?

Lefty
11966  Forum 2005-2010 (read only) / Interfacing / Re: graph in matlab on: January 13, 2011, 04:04:37 pm
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ok...then how to connect the arduino with matlab in order to send the data to matlab?

That link already exists. The arduino sends serial data via USB to a virtual comm port number. Any PC application that can read and write to a comm port has the means to communicate with an arduino that has an appropriate sketch running on it. The Arduino doesn't care if the serial data it can send is going to the arduino IDE serial monitor or any other PC application that has access to the comm port. That make sense?

Lefty
11967  Forum 2005-2010 (read only) / Interfacing / Re: Help or guidance for a magnetic stripe reader proj on: December 23, 2010, 11:54:56 am
Not only do you have the problem of low level voltage, millivolts, the data format includes a clock and data that have to be decoded and seperated. Your best bet would be to find a surplus card reader (I found one for $5 once). If you search around this forum you might find a posting on someone that wrote a sketch to read such a reader.

Lefty
11968  Forum 2005-2010 (read only) / Interfacing / Re: max with a rotary encoder on: February 23, 2009, 02:21:19 pm
I think a quadrature rotary encoder with a push button is a very nice and intuitive user interface. Turn encoder to see function options available and press switch to select it. However as others have said a quality rotary encoders seem to be costly and the cheap mechanical one I got is not very precise in it's detents Vs steps.

I read one article about converting a stepping motor to act like a rotary encoder. It required a little external components but sounded like a need project to play with. Some steppers have very nice feeling 'jogs' and with a nice heavy knob might have a very nice feel.

Lefty
11969  Forum 2005-2010 (read only) / Interfacing / Re: 8-bit formula conversion to 10-bit formula. on: December 31, 2010, 02:39:49 pm
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I use USB when debugging, etc, but for actual use, I use an external power supply. When using external power, my understanding is the on-board voltage regulator maintains a more accurate (?) 5v rail, is that the case?

That is going to be very specific to every different PC and every different Arduino board. The on-board +5vdc regulator has a voltage tolerance specification and the USB standard allows a certain amount of variation in it's +5vdc power and still be in compliance. For the best accuracy possible one has a few options, use a external tight tolerance hardware reference voltage reference chip. Or one could make measurements of their boards regulator voltage and have a calibration correction function in their code. The A/D feature in the Arduino is very useful but not by any means instrumentation quality. For demanding applications one should probably look into external I2C A/D converters that offer more resolution, better reference voltage, better low noise specification, etc.

Lefty
11970  Forum 2005-2010 (read only) / Interfacing / Re: new to this and looking for some advice please on: December 27, 2010, 05:44:10 pm
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You need to undertand that no-one here wants you cause your specimens any harm through your learning experience.

But I hate snakes and lizards aren't real high on my list either, so should I just bow out because of bias.  ;D

Lefty
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