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46  Using Arduino / Microcontrollers / Re: Arduino Uno vs Launchpad energy consumption on: January 29, 2013, 08:21:09 pm
Any real life experience?

You can make an arduino/avr consume more current than a msp430 and you can make a msp430 consume more current than an arduino/avr: current consumption is more software dependent than hardware dependent, regardless of how chip vendors tell you otherwise.

What's truly unique about msp430 is its ability to start its crystal oscillator almost instantly. No one has been able to do that.

Otherwise, quite a few chips have come close to msp430 or beat it in terms of current consumption/Mhz.
47  Using Arduino / General Electronics / Re: Decoupling shift registers on: January 29, 2013, 06:10:47 pm
How likely am I to have problems without them?

Quite unlikely.
48  Using Arduino / Project Guidance / Re: Measuring voltage over a resistor on: January 29, 2013, 06:09:25 pm
How can I do that?

Find an opamp with common mode voltage range beyond its supplies. Likely an instrumentation opamp.
49  Using Arduino / Microcontrollers / Re: Starting Out On AVR Programming on: January 29, 2013, 07:30:30 am
If so, what do I need to do so that it can accept AVR code?

I would get a standalone programmer. They are so cheap now and provide you with the flexibility to move up to a new world without arduino.
50  Using Arduino / Project Guidance / Re: Where can I find gray LCD (like the one in a calculator) on: January 29, 2013, 07:28:25 am
Where can I find gray LCD (like the one in a calculator)

From a calculator?

I buy cheap calculators from Walmart and take them apart. They go for about $1 each.

The issue with those types of calculators is that the ribbon is not solder-able. They are instead taped to the pcb. So your own option is to sand away the paint and then solder fine copper wires to the traces on the pcb.

But otherwise it works like a charm.

You can reuse the keypads + casing too.
51  Using Arduino / LEDs and Multiplexing / Re: Hc595 7 Segment on: January 29, 2013, 07:21:43 am
The answer depends on how you wire them up.
52  Using Arduino / Motors, Mechanics, and Power / Re: Very precise servo motors on: January 28, 2013, 08:50:40 pm
You can use a stepper + an optical encoder (5000 line encoders are fairly reasonable in prices), aka a real servo.
53  Using Arduino / Programming Questions / Re: Generating separate square-wave oscillators on: January 28, 2013, 08:46:23 pm
Frequencies, lets say 1, 1.5, 2 and 2.5 Hz.

Fairly easy.

1) set up a free running timer (a timer with auto reloading works as well).
2) In the isr, advance four counters, each corresponding to one of the four frequencies above.
3) Flip a pin as a result of the frequencies.

Something like this:

  static unsigned long counter_1000ms=0, countre_1500ms=0, ...;
  counter_1000ms += 0x10000ul; //for free-running 16-bit timer
  if (counter_1000ms >= F_CPU) {
    counter_1000ms -= F_CPU; //reset the counter
    //flip the pin for 1hz

  counter_1500ms += 0x10000ul; //for free-running 16-bit timer
  if (counter_1000ms >= F_CPU * 2 / 3) {
    counter_1500ms -= F_CPU * 2 / 3;
    //flip the pin for 1.5hz

You can pre-define the constants to make it easier to read.
54  Using Arduino / Project Guidance / Re: enum as function parameter on: January 28, 2013, 08:41:10 pm
what's causing this problem, and why putting the enum and their related functions in a separate header file is the recommended solution.

Whoever proposed that has no understanding of C.
55  Using Arduino / Sensors / Re: Clever low voltage monitor (no external components) on: January 28, 2013, 06:30:44 am
Nothing new. It has been done for decades.
56  Using Arduino / Programming Questions / Re: Stepper Absolute Position ... how to on: January 27, 2013, 08:05:38 pm
I just need to set the Zero (starting Point) then I just have to know where I am and where I want to go.

Without a position sensor, you wouldn't know where you are: all you know is where you have told the stepper to go. Whether the motor is there or not is an unknown, unless you have a position sensor.
57  Using Arduino / Programming Questions / Re: Stepper Absolute Position ... how to on: January 27, 2013, 06:02:36 pm
Stepper Absolute Position ... how to

With a position sensor - encoder or a pot.
58  Using Arduino / Motors, Mechanics, and Power / Re: H bridge using 4 PNP transistors. on: January 27, 2013, 06:01:34 pm
Is it even possible?

Yes. Pretty much any combination of PNP/NPN can be made to work.
59  Using Arduino / LEDs and Multiplexing / Re: Arduino PWM only putting out 3.6Volts on: January 27, 2013, 05:54:50 pm
a series 20ohm resistor,

You probably want to read the datasheet.
60  Using Arduino / General Electronics / Re: OpAmp + Voltage Divider circuit on: January 27, 2013, 05:52:57 pm
But, I heard that high resistance voltage divider is not going to give high precision voltage output.

Yes. But that can be mitigated effectively and inexpensively.

My question is - is it possible to use a lower resistance values resistors with an op amp in voltage follower configuration to yield high precision and low power dissipation voltage divider, considering an OpAmp has Infinite input impedance?

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