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10561  Using Arduino / Programming Questions / Re: Why does Arduino tend to use such low baud rates in tutorials? on: May 16, 2011, 09:52:07 pm
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Is there any general reason to use lower baud rates (disregarding the case where you need to interface with a device that doesn't support higher rates)?


No, not if the device can handle the rate. Keep in mind that the highest baud rate puts a burden on speed of processing receive data for the arduino. the serial receive buffer is 128 bytes in size and if ones loop sketch is too slow it's possible to drop characters if lots of data is coming in at the highest possible baud rate. So while the highest baud rate can help your sketch run faster on the transmit side, it brings a burden on processing the receive data stream at the same time. It's really application dependent, no one size fits all cases.

Lefty
10562  Using Arduino / Installation & Troubleshooting / Re: Arduino Uno Communications Problem Solved on: May 16, 2011, 09:42:29 pm
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Hope this helps someone. This is supposed to be fun after all right! - Kevin 

I'm glad you figured it out and shared your solution, I'm sure it will help someone one someday.

Lefty
 
10563  Using Arduino / Programming Questions / Re: Why does Arduino tend to use such low baud rates in tutorials? on: May 16, 2011, 09:38:38 pm
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Anybody know why the defaults are set so low?

There is no specific default. Bootloader baudrate has changed over time but that has no relationship over what specific baudrate various authors used in their sketch examples. I tend to use 57600 baud in most of my projects.

Lefty
10564  Development / Other Hardware Development / Re: ATMEL Mega1284P evaluation board avalible on: May 16, 2011, 06:03:20 pm
Lefty, i don't follow... It seems like you are saying that a jumper needs to be moved to switch from wall wart to USB power. Or does your jumper switch from auto-switching to not auto-switching?


I proposed eliminating the auto-voltage switching logic altogether. Instead replace with a simple 3 pin SIP male pin header and a two position jumper clip. In one position the boards power is coming from the on-board +5VDC regulator, in the other jumper position the boards power comes from the USB +5vdc source. You decide how you want to power the board and place the jumper appropriately. A two position manual switch could also work just as simple as it does in the Seeeduino board designs. How the board is powered has no bearing on if you are using the usb serial function or not, if the board has power the usb can function period.

Edit: What I proposed is to go back to the design that arduino used with the  Diecimila board.
http://arduino.cc/en/Main/ArduinoBoardDiecimila

Schematic: http://arduino.cc/en/uploads/Main/Arduino-Diecimila-schematic.pdf  Note the power selection jumper in the lower left hand of the drawing.


Lefty
10565  Using Arduino / Programming Questions / Re: Analogue to digital conversion for volume control on: May 16, 2011, 05:52:37 pm
Pretty poor picture. But I would guess that you have the pot wired wrong. Usually the variable resistance is the middle terminal, not one of the end terminals.

Lefty
10566  Development / Other Hardware Development / Re: ATMEL Mega1284P evaluation board avalible on: May 16, 2011, 05:28:55 pm
I find it mildly convenient to be able to take my computer over to my running project, hook up my USB cable, upload new code, then disconnect shortly thereafter without the project having to reboot. Would your solution allow that?

Yes, that would still function as you stated.

As far as power switching, the arduino auto-voltage switching remains powered by the external source if power is on both usb and the external power connector at the same time (external has priority), so that would have no bearing on what you are asking to do, the board would not reboot because you removed the usb connector.

Lefty
10567  Using Arduino / Project Guidance / Re: Changing the clock frequency of an Arduino Mega 2560 on: May 16, 2011, 05:23:37 pm
Well in theory it might work. The bootloader would have to be recompiled to work at the new frequency, something not able to be done inside the arduino IDE. A new board entry for the boards.txt file defining this new configuration is needed, but that is simple. Not sure how accurate the millis(), micros(), and delay() functions would be with your new frequency, so that would have to be looked into. But the hardware side is just a simple swap out and adding the padding caps, however smd desoldering/soldering in not for the inexperienced.

Lefty

10568  Development / Other Hardware Development / Re: ATMEL Mega1284P evaluation board avalible on: May 16, 2011, 05:07:30 pm
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If the device is going to live somewhere away from a PC ou need to power it, but for the occasional trip to the PC to be updated or whatever it comes in very handy not to have to go searching for the wall art.

What I proposed doesn't prevent that, it just requires moving a jumper clip from one position to the next position. What's not handy about that?

Another example of the auto-voltage lameness. Assume your project is powered externally and is independent to a PC. Why power up the FTDI or 8u2 chip? Check out the Seeeduino design for power selection, manual two position switch for usb/external power and FTDI power source is hardwired to the USB connector only. That's good functional design.

Lefty
10569  Using Arduino / Project Guidance / Re: Powering Arduino with 12V, 7.5Amp - doable? on: May 16, 2011, 05:00:58 pm
I would still not run 7.5 amps through the arduino ground pin(s) to the high current load. Better to have separate properly sized +12 and ground wires to the high current load and then just a separate +12v and ground to the arduino external power connector.
10570  Community / Bar Sport / Re: Rant - Destroying an Arduino EEprom on: May 16, 2011, 03:33:45 pm
I would just call it an example of digital masturbation.

Lefty
10571  Using Arduino / Programming Questions / Re: Continuous Rotation Servo + PIR Sensor Help! on: May 16, 2011, 03:28:35 pm
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On the library i can only find rotation codes for non continuous servos (e.g codes that rotate the servo a fixed amount of degrees either to the left or right) and so forth, could someone direct me to a library concerning continuous rotation servos?

Same library is used, same signal to the servo. However while a normal servo rotates and stops given a signal from 0 (degrees) to 180 ( degrees). The same commands going to a modified servo would result in  0 = full speed in one direction, 180 = full speed on the opposite direction, and 90 = stop. Values sent between 0-89 or 91-180 would result in continous rotatation at a specific speed. Note that the 90 degrees = stop may have to be tweeked to find the specific stop condition for your specific servo due to calibration variation between servos.

Lefty
10572  General Category / General Discussion / Re: What Board to Buy? on: May 16, 2011, 02:01:42 pm
Actually the arduno boards a pretty affordable so don't think that your first arduino purchase will be your last and therefore buy the biggest first. The standard ardunio 2009 or Uno is probably the best starting point.

 You didn't state if you are new to hardware electronics, but if you are your first purchase should be a decent digital multimeter as you will be responsible for proper wiring of components and checking for proper voltages, etc. Those darn electrons are invisible and you need to the meter to tell you where they are hiding and how many are ready to launch into creating problems for you.

Lefty

10573  Using Arduino / General Electronics / Re: Amplifying a signal using an Op-Amp on: May 16, 2011, 01:44:31 pm
From your link, it looks like with 6V this give me about 1/3 Watt, and with 9V I can do about 1/2 Watt.  So together with the 1/2 W speaker from SFE (above), would that get me the volume level I'm looking for?

Most likely, however speaker efficiency and proper speaker baffling/mounting enter the picture for actual SPL sound level output Vs audio electrical power consumed.

Also, If I go with the 9V version, can I just feed it directly from a 9V wall wart, or would I need a regulated power supply for it?

Yes you can power it directly from the a 9vdc wall wart. However you may have to add additional filtering caps if there is too much 60/120hz ripple voltage coming from the wall wart. I've used LM386 chip in some projects in the past and they do work well, however hum and other low level noise can be a problem if circuit layout, signal routing and power quality are not up to snuff. It's all about learning to solve the problems as you come across them if you want to learn and build this kind of stuff yourself. Otherwise buy pre made solutions.

Lefty

10574  Using Arduino / General Electronics / Re: Amplifying a signal using an Op-Amp on: May 16, 2011, 01:43:52 pm
From your link, it looks like with 6V this give me about 1/3 Watt, and with 9V I can do about 1/2 Watt.  So together with the 1/2 W speaker from SFE (above), would that get me the volume level I'm looking for?

Most likely, however speaker efficiency and proper speaker baffling/mounting enter the picture for actual SPL sound level output Vs audio electrical power consumed.

Also, If I go with the 9V version, can I just feed it directly from a 9V wall wart, or would I need a regulated power supply for it?

Yes you can power it directly from the a 9vdc wall wart. However you may have to add additional filtering caps if there is too much 60hz ripple voltage coming from the wall wart. I've used LM386 chip in some projects in the past and they do work well, however hum and other low level noise can be a problem if circuit layout, signal routing and power quality are not up to snuff. It's all about learning to solve the problems as you come across them if you want to learn and build this kind of stuff yourself. Otherwise buy pre made solutions.

Lefty
10575  Community / Bar Sport / Re: My electric blanket doesn't work ... on: May 16, 2011, 01:35:55 pm
When it comes down to features Vs reliability, put me down for reliability first. However it's not always easy to determine that when purchasing stuff like electric blankets in stores and higher price doesn't always mean more reliable either.

I recently bought a new refrigerator from a Sears store. The salesman commented unsolicited that they don't make the appliances as reliable as they use to. Of course he was using that as a hook to try and get me to purchase the 'extended warranty'.  smiley-roll-blue

Lefty
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