arduino pin outs with relays

Forum 2005-2010 (read only) Hardware Troubleshooting
1

I have a relay that is setup and connected to the arduino duemilanove board in such a way that when 5 volts is applied via the output pins it switches the relay on. I use the digitalwrite command to turn on the pins. my problem is that the only pin that actually will power it is pin 13 with the led built in. I cannot figure out why all the other pins do not work. Using a voltmeter they all read 5 volts but as soon as i connect them in series with my resistor the voltage drops to 2. This happens with all pins except the led pin 13. Any thoughts as to why or how to remedy? thanks

2

Without seeing your code and/or actual wiring drawing it's hard to guess. Are you using a proper pinMode(pin, mode) statement for each of the other output pins you are trying to use?

Lefty

3

Also how much current are you trying to draw?

4

I just fixed the same problem with my arduino about a minute ago lol. I'm using this Arduino Playground - HomePage circuit to power up high voltage LEDs. I was testing it with modifications I had made on the blink sketch and used loops to power on and off all of the LEDs. Mind you I forgot to initialize all the pins except for 13 so I thought there was something about the led on the arduino on the resistor in the circuit that changed everything. They did light just not as much. Kind of embarrassing as I had people over to help me finalize it for a show tomorrow and I couldn't get it to work.

Here's the code I'm using now if anyone is interested.

void setup() {
  for (int i=1; i <= 13; i++)
  { 
  pinMode(i, OUTPUT);  // declare the ledPin as an OUTPUT
  }

}

void loop() {
delay(500);
for (int i=1; i <= 13; i++)
   digitalWrite(i, HIGH);
delay(500);
for (int i=5; i <= 13; i++)
   digitalWrite(i, LOW);
}

Though it doesn't sound like code is the problem in your case, but I might be worth a look. It's not all too clear what's wired to what from your explications but voltage should drop in series, no ?