Home \ Help \ Search \ Login RSS

Welcome, Guest. Please Login

This forum is now READ-ONLY! Please visit http://forum.wiring.co/ for the new forum.

Wiring ForumWiring HardwareTroubleshooting › 2.5 Volt?

Page Index Toggle Pages: 1
2.5 Volt? (Read 6657 times)
10/17/07 at 16:24:39

Kars   Offline
YaBB Newbies
Team Vossius
Amsterdam

Posts: 19
*
 
Hi there

I tried to turn on a led (just turn on, not blinking) with this schematic, but my led doesnt go on for the full 100%, but it burns only on ±50%. So i decided so      measure the voltage with my multimeter. And it says that there is only 2.5V  Huh
How is this possible? I want 5V Tongue
 

Buildig the same as Titus ^^
IP Logged
 
Reply #1 - 10/17/07 at 21:27:18

Alan_Kilian   Offline
Full Member
Wiring? It looks like
Java to me.

Posts: 118
***
 
You are probably getting 5 Volts out of the processor, but the LED
has a 2.5 Volt forward voltage drop, so your meter reads 2.5 Volts.
This is normal.

Remove your LED and measure it and you'll probably see 5 Volts.

If it's too dim, you need to use a smaller resistor.

Can you post your program and your resistor value as well as
the kind of LED you are using?
 
IP Logged
 
Reply #2 - 10/18/07 at 08:59:31

Kars   Offline
YaBB Newbies
Team Vossius
Amsterdam

Posts: 19
*
 
When i removed the led i read 4.5V instead of 5V. (I measured directly from digital pin 0 (set as output) to ground)
I use 3 resistors from 82 ohm in serie, so i get 246 ohm
And I use this led

My program code is realy simpel:

Code:
void setup()
{
}

void loop()
{
 digitalWrite(0, HIGH);
 delay(10);
}  

 

Buildig the same as Titus ^^
IP Logged
 
Reply #3 - 10/18/07 at 10:22:58

worapoht   Offline
YaBB Newbies
Thailand

Posts: 21
*
 
hi Kars,
the code need to initiate pin as OUTPUT before..
if not, digitalWrite just enable internal pull-up resistor and current was limited.
that's why LED not fully bright as should to be..

void setup()
{
  pinMode(0, OUTPUT); // sets the digital pin as output
}

void loop()
{
digitalWrite(0, HIGH);
delay(10);

 
IP Logged
 
Reply #4 - 10/18/07 at 12:07:51

Kars   Offline
YaBB Newbies
Team Vossius
Amsterdam

Posts: 19
*
 
worapoht wrote on 10/18/07 at 10:22:58:
hi Kars,
the code need to initiate pin as OUTPUT before..

Yeah thanks Cheesy That did the trick
I feel now a bit stupid :|
 

Buildig the same as Titus ^^
IP Logged
 
Reply #5 - 10/19/07 at 18:57:57

Alan_Kilian   Offline
Full Member
Wiring? It looks like
Java to me.

Posts: 118
***
 
Yippeeee! It always feels great when someone gets something working.
 
IP Logged
 
Reply #6 - 05/14/08 at 07:12:53

lafeecerule   Offline
YaBB Newbies
I Love YaBB 2!

Posts: 4
*
 
So, if you set the pin as output do you get 5V from your reading? I can't find the voltage of the output from anywhere else in the website.
 
IP Logged
 
Reply #7 - 05/14/08 at 14:20:45

Kars   Offline
YaBB Newbies
Team Vossius
Amsterdam

Posts: 19
*
 
If you set your pin as an output and you put in HIGH, then the voltage will be 5V on the pin. If you set the pin LOW, the voltage will be 0v (ground)
 

Buildig the same as Titus ^^
IP Logged
 
Page Index Toggle Pages: 1