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10561  Using Arduino / Interfacing w/ Software on the Computer / Re: external 5V at Vin pin, and USB connection - UNO board on: February 27, 2011, 01:39:11 am
The schematic helps a lot, you got a lot of stuff going on there. Now a problem is you are routing +5vdc shield voltage (Vcc) to the Arduino uno via the shield's Vin pin? That won't work, the Vin pin on the Uno has to have at least 7 vdc applied to it to power the input of the Uno's 5vdc regulator.

 I thought you might to powering the uno board by wiring the shields vcc to the +5vdc pin on the shield connector, thus then having the two regulator outputs tied together problem I mentioned, if you were also routing voltage via the Vin pin, which your aren't.

This is all giving me a headache.  smiley-grin Anyway I still don't see a perfect way to power the system and still be able to utilize USB power when you wish. But what you have right now is flawed because the uno's regulator's input needs to be 7vdc or higher to operate correctly.

10562  Using Arduino / Project Guidance / Re: Question about shilds on: February 27, 2011, 01:03:34 am
would that work is there a limit?

Well not a designed in limit. However one can't use shields that use any of the same I/O pins. One can't stack shields such that they in total require more +5vdc current then the Arduino board can safety supply. One can't stack shields is the lower shield has extra tall components that mechanically interfere with a top shield board. One can't stack on top of a shield that has connectors or controls that need top surface access, etc, etc.

So it's not a simple question.

10563  Community / Bar Sport / Re: What else offer an Arduino MEGA beside the big amount of ports? on: February 27, 2011, 12:59:25 am

it has more pins which can do PWM, than the arduino, right?

From the reference:

On most Arduino boards (those with the ATmega168 or ATmega328), this function works on pins 3, 5, 6, 9, 10, and 11. On the Arduino Mega, it works on pins 2 through 13. Older Arduino boards with an ATmega8 only support analogWrite() on pins 9, 10, and 11. You do not need to call pinMode() to set the pin as an output before calling analogWrite().

More timers means more PWM pins avalible.
10564  Using Arduino / Project Guidance / Re: 10x10 LED grid on: February 27, 2011, 12:26:41 am
In a 5x5x5 led cube I build I really like the use of the 16 bit constant current output pins shift regesters.

The use of programmable constant current output pins solve a big design hurdle as led brightness becomes independent of the scanning rate you use. Just one resistor needed for each 18 bit device so current limiting becomes adjustable and minimizes component count.

Anyway one of these devices would handle the 10 row common connected leds (requiring only 3 arduino output pins), then you just need 10 arduino output pins to drive the common column led connections. Use the MsTimer2 library to setup up a scanning interrupt routine and it becomes a pretty straight forward project.

10565  Using Arduino / General Electronics / Re: Please check my circuit for errors.. on: February 27, 2011, 12:12:52 am
The cap helps keep noise from the reference and therefore is often used to get cleaner analog readings.

When using one of the INTERNAL options AREF is actually connected to this internal reference, if it is also connected to say 5v you have 5v->1.1v (or whatever is selected) which is bad.

You can connect Vs to AREF but have to be very careful never to use an INTERNAL reference.


Actually the Arduino reference has instructions on wiring a series resistor between the Aref pin and any external voltage reference being used. That would prevent damaging current level flows in case of misuse of the analog reference command.

10566  Using Arduino / Microcontrollers / Re: Arduino faster than the Mega? on: February 27, 2011, 12:07:15 am
Does anyone know if the Arduino 'company' plans on offering both the dip and smd versions of the Uno in the future?

 It would a real shame if they didn't continue to offer a dip mounted version as that takes away some of the flexiblity and ease of repair, both important features in my opinion.

10567  Using Arduino / Installation & Troubleshooting / Re: No green light on: February 27, 2011, 12:01:32 am
The relentless march of the Ebay knock-offs.......  smiley-wink

Blue is the new Green
10568  Development / Other Hardware Development / Re: Annotatable (hopefully annotated) Arduino Schematics now available! on: February 26, 2011, 11:57:46 pm
Britton, this is Way Cool!

How did you do this?  I'd love to use this approach to explain some other stuff I am working on, such as this:

And this:

WhatIf there was a similar thing with a image of the physical Arduino, with "normal" voltage readings at different points, for those of us trying to fix an abused or unlucky Arduino??

Wow. So much stuff to learn about...

Hey Terry;

 I bought one of those brick shield boards and several 'brick' modules about a year ago. I really like the concept and the quality seemed pretty good, but I stopped buying modules for three reasons.

Most important reason is none of the sellers publishes schematic drawings of the modules, documentation on a whole really sucks on this product line. That's not a big deal for a button brick or a pot brick, but when you get to a mic/audio brick it's impossible to actually tell what kind of signal output to expect or how much amplification range one has, etc.

 Second problem is that some of their example sketches for some of the bricks are downright dishonest in that they are not actually testing the module for it's primary purpose, but rather just say lighting a led to say it probably is functioning somewhat. That added to the zero documentation can make it very difficult to actually utilize some of their brick products.

Lastly for being Asian sellers, selling on E-bay, their prices seem very high relative to all the other electronic components and modules I buy from Asia on E-bay.

Looking forward to your thoughts and comments on this product line?

10569  Using Arduino / LEDs and Multiplexing / Re: Arduino board LED and external LED on pin 13 blinking at different rates on: February 26, 2011, 11:44:46 pm
Wow.. I was ALMOST ready to say "That's Impossible".. but I have learned the hard way NOT to say that  smiley

I ALMOST wish you hadn't answered this already...

It ranks up there with the unknown, hidden from view, left-handed threaded access screw.

10570  Using Arduino / Project Guidance / Re: Measuring the power produced by a solar panel on: February 26, 2011, 11:37:08 pm
All extremely good points and some assumptions challenged which I always like. So on the basis that I'm not going to assume 1amp what's the right way to go about this in order to measure current and voltage. I can use voltage in parallel to the circuit but presumably to measure current I have to be in series - isn't putting my arduino in the path of potentially 1amp and up to 20v going to end up with some blue smoke?

If your solar cell panel is ground based, that is if it's negative lead is wired to everything else's (charger, battery, arduino, controller?,etc) ground then it's pretty simple. You wire a low ohm resistor, say 1 ohm (get a precision one) and wire the resistor in series from system ground to the solar panels negative lead. Now you can wire a measurement lead from the solar end of the resister to a arduino analog input pin. A analogRead() value of one volt (205 counts) would mean one amp of current is flowing. You can then use a map statement to convert A/D counts into current range. You already know about using two series resistors to form a voltage divider to allow the Arduino to measure panel voltage scaled to arduino safe voltage levels. For time measurements you could either add a $15 RTC/calendar chip to your arduino or use the a time library. It's not difficult as your solar panel is not a high current device. If we were talking panels of 10s of amps or higher then there are better ways to sample and measure DC current.

10571  Using Arduino / Motors, Mechanics, and Power / Re: Some 'power' questions... on: February 26, 2011, 11:20:13 pm
I would have to respectfully disagree with selecting the batteries after getting something working without batteries, especially a robot.

Well honorable people can disagree on this point I'm sure. However the battery is going to be a very expensive item and fundamental to the success of the project and until I actually had a chance to measure worst case current draw of all the heavy current consumers in actual operation, I would be uncomfortable selecting and purchasing the battery first. Possibly only to learn later during testing that it had too low a current draw capacity, or even to learn later that a smaller battery at half the price would have the current draw and duration spec I had in mind. I never 100% trust current consumption specs for many components. Or as Regan said trust but verify.
However your way may work better for you.

10572  Using Arduino / General Electronics / Re: Please check my circuit for errors.. on: February 26, 2011, 11:10:48 pm
Don't connect AREF to Vcc, it'll may be damaged.  Just have a decoupling cap to ground from this pin.
Just curious, why do we connect a cap there?

Because that pin is connected internally to the reference voltage used for the A/D converter used for analogRead() statements. So the extra noise filtering from the cap will help improve the accuracy of the A/D measurements.

10573  Using Arduino / Installation & Troubleshooting / Re: No green light on: February 26, 2011, 10:55:38 pm
Hi all,

I'm very new to all this, so please excuse any questions that seem very basic.

I bought an Arduino Mega 2560, and plugged it into my computer's USB today, but I didn't get a green light. Instead I got a blue light labeled ON, and a blinking orange light labeled AREF.

Is my board faulty?

Regradless of what color the ON led is, if it's lite up it means the board has power on, as it should being plugged into a live USB port. The led near the Aref pin, is the pin 13 activity led and blinking means it probably has the sample blink sketch loaded on it and it's running.

Start loading up other example sketches from the Arduino IDE examples files. Oh, and have fun.  smiley-wink

10574  Using Arduino / Programming Questions / Re: Timer interrupt question on: February 26, 2011, 10:45:10 pm
Rather then having to learn low level controls for simple timer applications, I have just used the MsTimer2 library in my projects that required timed interrupts. It is simple to understand and use.

10575  Using Arduino / Microcontrollers / Re: how to read/retrieve eeprom's content on: February 26, 2011, 10:33:48 pm
how to read/retrieve other code from the board ? e.g. I uploaded the code for a night light (light sensor+LED) project, any way to retrieve that code

After you upload a sketch into the board and then close out the arduino IDE it asks you if you want to save the sketch. Normally you would say yes and there will be a folder created for your sketch so that later you may upload it again, or modify it, etc.

Your Arduino board and the Arduino IDE running on your PC form a system for development. The PC is used to save sketches and library routines and other aids to programming your board. The board just runs whatever sketch was last loaded. It has non-volatile flash memory so even if you power off the board the next time you power it up it will run the last program loaded into it. It's a simple and sweet platform that is easy to learn yet effective enough to keep you learning for a long time to come.

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