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1246  Using Arduino / General Electronics / Re: routing power from solar source to consumers over a garden on: March 25, 2013, 05:09:44 pm
For 5V DC over 24 gauge copper (like the size in ethernet cables) for every 10 feet of distance you lose .01V at 20ma or .1V at 200ma. Hardly a concern.

http://www.calculator.net/voltage-drop-calculator.html


1247  Using Arduino / Project Guidance / Re: construction Laser level for digger on: March 24, 2013, 12:45:58 pm
IR receivers are pretty tolerant when it comes to the pulse frequency.
1248  Topics / Product Design / Re: Itead, Members with Experience... on: March 23, 2013, 11:53:48 pm
GerbV (http://gerbv.geda-project.org/) works well for me on Linux. Have not used the Windows version but it's available.
1249  Using Arduino / Project Guidance / Re: Arduino Uno: How would I input a priority encoder? on: March 23, 2013, 11:48:33 pm
I think you want (n = 4; n > 1; n--)
1250  Using Arduino / Microcontrollers / Re: Arduino as ISP with the ATtiny85 on: March 23, 2013, 11:41:29 pm
I've not had problems with MITs core; have burned many ATTiny85s and 84s.

OPs steps appear to be correct. Probably a silly wiring mistake or maybe a bad chip?
1251  Using Arduino / Microcontrollers / Re: Arduino UNO talking to a attiny44 via RS-485 on: March 23, 2013, 11:35:59 pm
You haven't really described what you're communicating. If you're just sending small messages every few seconds or so then the path you're on (RS-485 serial communication) is fine.

Might want to poke over and look at the EasyTransfer library. It is ATTiny compatible (or generally doesn't care what the hardware is) but the 4K of space on your ATTiny44 will make things extremely tight; a basic sketch is 3.7K. You might need to jump to an ATTiny84.
1252  Using Arduino / Project Guidance / Re: automating wire twisting machine on: March 23, 2013, 11:04:33 pm
maxbotix.com might be the only option. They are very well supported and documented.
1253  Using Arduino / Project Guidance / Re: using nokia 5110 lcd screen and SD card reader/writer with SPI on: March 22, 2013, 01:45:54 pm
The SD card library is written to use hardware SPI. The Adafruit_PCD8544 library is written to use software SPI.

Is it possible to use both software and hardware SPI when connected to the hardware SPI pins? I've never tried myself.
1254  Using Arduino / Microcontrollers / Re: burning non standard files to attiny on: March 22, 2013, 02:06:34 am
The Makefile is a list of instructions, read by "make", to build the .c and .h files into the .hex file. Unless you're changing the source code there's no need to rebuild the .hex file.

The .pl file is a Perl script and appears to be used to read codes with the TV B Gone.

To burn the .hex file to the ATTiny you need to read up on using avrdude.
1255  Using Arduino / Project Guidance / Re: using nokia 5110 lcd screen and SD card reader/writer with SPI on: March 22, 2013, 01:31:37 am
There's nothing too magical other than knowing the various naming schemes of the SPI pins. Explaining the connections would be much simpler if you could provide a link to the exact SD card breakout.

It's important to distinguish between hardware SPI and software SPI. When you're using hardware SPI you're using pins 13, 12, 11, and 10 on the Arduino and the SPI library. If you're using software SPI you're usually using the ShiftOut and Shiftin functions and can use any pins; transfer rates will be much slower.

In general though, the clock (usually called CLK, CK, or SCK) pins are all connected together. The master's data in pin (MISO, master in slave out, hardware pin 12 on the Arduino) is connected to the data out pins (usually DO or SO) on each of the devices. The master's data out pin (MOSI, master out slave in, hardware pin 11) is connected to the data in pins (DI or SI) on the devices. Then as you mentioned each device gets a different connection for the chip select (CS or SS) from the Arduino (hardware pin 10).

The last thing to watch out for is level conversion. Assuming your Arduino is running at 5V you have to make sure that outgoing signals (the Clock, MOSI, and CS pins) are converted to 3.3V before it reaches any of the devices (SD cards and 5110 displays are both 3.3V devices). Incoming 3.3V signals (connected to the Arduino MISO pin) from the devices will still be treated as a digital high value by the 5V Arduino; they don't need to be translated up to 5V. Adafruit's tutorial with the 5110 explains how to do the 5V to 3.3V conversion with a 4050 IC.
1256  Using Arduino / Motors, Mechanics, and Power / Re: Motor Controllers for car seat motors? on: March 21, 2013, 03:21:32 pm
Pololu describes their parts as "drivers" and "controllers". Their controllers are drivers with extra microprocessors onboard; if you're using them with an Arduino that's usually extra goo that you don't need and at a higher price.

http://www.pololu.com/catalog/product/707 will run two motors.
http://www.pololu.com/catalog/product/705 will run one.

Also, we're assuming you need to drive these motors in both directions. If you're only driving them in one direction then you can do this with a single mosfet for much cheaper.
1257  Using Arduino / Project Guidance / Re: Arduino Uno: How would I input a priority encoder? on: March 21, 2013, 02:23:01 pm
Whoops. Those "&=" should be "|=".

I assure you this is the first time I've ever made a programming mistake.
1258  Using Arduino / General Electronics / Re: How to show internal pullups on a schematic? on: March 21, 2013, 11:34:28 am
If the pin/input has a name you put a bar over the top of it to indicate that the logic is reversed (that it has an internal pullup). Shouldn't that be sufficient?
1259  Using Arduino / Project Guidance / Re: Arduino Uno: How would I input a priority encoder? on: March 21, 2013, 01:45:45 am
See http://playground.arduino.cc/Code/BitMath

Code:
void loop() {
  val = 0;  // initialize to zero

  if( digitalRead(onepin)== HIGH)
    val &= B00000001;
  if (digitalRead(twopin) == HIGH)
    val &= B00000010;
  if (digitalRead(fourpin) == HIGH)
    val &= B00000100;

  delay(100);

  Serial.println(val);
}
1260  Using Arduino / Sensors / Re: Autonomous Lawn Mower Navigation on: March 20, 2013, 12:32:46 am
Essentially we have one stationary GPS that assumes the first point it reads is the point it is at and all other data it receives has error in it. It calculates this error and sends it over to the "rover" so that it may calculate what the error is and subtract it from its own coordinates.

After you try this please come back and tell us how well it worked. I'd considered trying it out myself but ... too many projects.
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