Go Down

### Topic: Basic circuits help (Read 4177 times)previous topic - next topic

#### wes000000

#15
##### Jan 30, 2014, 10:04 pm
The problem is that there are two ways to skin the cat, but so long as the pin is always in a known state neither one is technically wrong. Although there are a number of reasons why I prefer using pull up resistors as opposed to pull down resistors (primarily since the Arduino - more specifically the microprocessor on the Arduino - has them built in) so you can activate internal pull up resistors via code and reduce the complexity of external circuits.

The pics you posted had pull down resistors so that pin 7 was at ground when the button was not pressed, then when you pressed the button, it brought pin 7 high (5V).

Alternatively it can be setup so that the pin sits at high when the button is not pressed, but tying pin 7 to 5V via a resistor and then when you push the button it makes pin 7 LOW (GND) by tying the other end of the button to GND.
"I have not failed. I've just found 10,000 ways that won't work." - Thomas A. Edison

#### wes000000

#16
##### Jan 30, 2014, 10:11 pm
Also you might try software such as this where you can easily play with simulated electronic circuits with no cost associated and no risk of damaging Arduino or components etc.

Not that the Arduino is specifically dangerous, but you could if not careful short a 5V digital pin to GND and that is a quick way to make things stop working. So its always nice with software because you can experiment with 0 risk.

Another good one: http://phet.colorado.edu/en/simulation/circuit-construction-kit-dc
"I have not failed. I've just found 10,000 ways that won't work." - Thomas A. Edison

#17
##### Jan 30, 2014, 10:12 pm
Quote
Are we dealing here with contrary definitions of what +5 (or -5) V means with respect to ground?

No, you are reading my descrition into your circuit, not my discussion of my circuit:
Quote

When enabled, and the pin is not connected to anything externally, the voltage becomes high.
If a switch is connected to that junction and connects to Gnd, the voltage becomes 0.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

#### tomisenbarger

#18
##### Jan 30, 2014, 10:43 pm
Ah, I did not see where you switched the antecedence in the conversation to refer to your other circuit.

Go Up