Show Posts
Pages: 1 ... 42 43 [44] 45 46 ... 79
646  Using Arduino / General Electronics / Re: I can lite an LED, but not a 3v flashlight bulb?? What is going on? HELP!!! on: July 18, 2013, 02:13:55 pm
Not counting for the negative temperature coefficient of tungsten. It might limit it to some extent. Still won't last very long though.
647  Using Arduino / General Electronics / Re: PNP and NPN beginner question on: July 18, 2013, 02:08:10 pm
The Vcc/Vee question is answered in the wiki:
"The ECL circuits usually operate with negative power supplies (positive end of the supply is connected to ground) in contrast to other logic families in which negative end of the supply is grounded. This is done mainly to minimize the influence of the power supply variations on the logic levels as ECL is more sensitive to noise on the VCC and relatively immune to noise on VEE.[20] Because ground should be the most stable voltage in a system, ECL is specified with a positive ground. In this connection, when the supply voltage varies, the voltage drops across the collector resistors change slightly (in the case of emitter constant current source, they do not change at all). As the collector resistors are firmly "tied up" to ground, the output voltages "move" slightly (or not at all). If the negative end of the power supply was grounded, the collector resistors would be attached to the positive rail. As the constant voltage drops across the collector resistors change slightly (or not at all), the output voltages follow the supply voltage variations and the two circuit parts act as constant current level shifters. In this case, the voltage divider R1-R2 compensates the voltage variations to some extent. The positive power supply has another disadvantage - the output voltages will vary slightly (±0.4 V) against the background of high constant voltage (+3.9 V). Another reason for using a negative power supply is protection of the output transistors from an accidental short circuit developing between output and ground[21] (but the outputs are not protected from a short circuit with the negative rail)."
648  Using Arduino / Project Guidance / Re: AC power Fluctuation Logging . on: July 18, 2013, 01:51:05 pm
"start getting them to work one-by one"

Which of "these things" do you have? If you had them before, why didn't you tell us?
649  Using Arduino / General Electronics / Re: Crystal behaving badly on: July 18, 2013, 01:20:46 pm
How are you measuring it? The MCLK in might be high impedance and easily disturbed. If you are getting 5 MHZ at the MClock out you are golden.
650  Using Arduino / Project Guidance / Re: a 4,8v reading on a loose pin 0? on: July 18, 2013, 01:14:14 pm
Could be the input on the serial to USB translator has a pullup
651  Using Arduino / General Electronics / Re: PNP and NPN beginner question on: July 18, 2013, 12:32:55 pm
My 3rd edition of "Reference Data for Radio Engineers" shows the cathode grounded and the control grids at *negative* voltage.
652  Using Arduino / General Electronics / Re: 2 ATMega Processors sharing a peripheral device (SPI ram) on: July 18, 2013, 12:25:32 pm
You might have to add an extra wire-OR'd control line so that each processor can signal when it is accessing the other chip. (Or send the CS signals to another input on each processor so that it can know not to access the chip)
653  Using Arduino / Programming Questions / Re: Serial communications question on: July 18, 2013, 11:59:56 am
Start a new topic and post your code.
I would guess you are comparing the character '1' to the integer 1, they are not the same thing.
654  Using Arduino / Project Guidance / Re: AC power Fluctuation Logging . on: July 18, 2013, 11:55:49 am
OK, so now get all the other pieces and start getting them to work one-by one.

To measure the AC line voltage you will need a transformer (that goes from your line voltage to about 5 V), full wave rectifier and a 1 uF or so capacitor. You might also need a voltage divider.

Once all the parts work separately, you can start combining them together.

You will proabably need a DVM before all this is done.
655  Using Arduino / General Electronics / Re: PNP and NPN beginner question on: July 18, 2013, 11:19:09 am
"For us digitals, GND is the most negative we deal with."
Obviously, you have never used ECL.

http://en.wikipedia.org/wiki/Emitter-coupled_logic
656  Using Arduino / Project Guidance / Re: A Mini Piano on: July 18, 2013, 11:16:05 am
Start here:
http://arduino.cc/en/Tutorial/Tone
657  Using Arduino / General Electronics / Re: PNP and NPN beginner question on: July 18, 2013, 11:12:58 am
Just the way current flows.

Electrons flow from the most negative terminal into the most positive. So for a positive voltage, electrons flow from ground into the positive terminal. For a negative voltage, the electrons flow from the negative terminal into ground.

To confuse things, we typically think of current flowing from positive to negative "Conventional Current Flow", which makes no practical difference unless you are designing semiconductor devices.
658  Using Arduino / General Electronics / Re: PNP and NPN beginner question on: July 18, 2013, 11:02:06 am
That is because positive voltages are more popular than negative ones. That is Ben Franklin's fault.
659  Using Arduino / Project Guidance / Re: A Mini Piano on: July 18, 2013, 10:23:33 am
You are the one that started with Do, Re, Mi...
He means that from Do (C) to Do(C) is an octave on the piano keyboard.
660  Using Arduino / Programming Questions / Re: How to do a particular operation for 1 ms using arduino. How to set the timer on: July 18, 2013, 10:01:25 am
Psst, Paul-
You mixed your millis() and micros() in your example...
Pages: 1 ... 42 43 [44] 45 46 ... 79