When I played with my relay before,they worked perfectly!
Have you tried hooking the relay directly up to the(a) power source? What happens? Be sure to only hook the relay up to a power source of the proper voltage. In other words, don't go hooking up a 5V relay to a 12V source to test it.
Now they can't even activate when the output pin goes up.
I got a LED working fine on that same exact pin.
Also checked the voltage using a resistor from that pin to ground and I get 4.7V wich is enough for the relay but still he ain't working
WhenI plug it in,the voltage I read is basicly 0. (I'd like to say once again; it was working before (before mean alone,relay only with nothing else)and now it's not(keypad is wired and a piezo,both are off while the relay should activate.
Hmm... That doesn't sound too good.
I tried using a transistor but my lack of skills in electronics showed me pretty quickly how bad I was :-/
If your relay could take more than 40ma when active then it might have damaged the output. If you can at all help it you want to use transistors for just about anything you hope to turn on/off with the arduino. I know, it might sound silly to go arduino -> transistor -> relay but it's for the best.
Does anyone has a simple bit of explanation on what would cause that and how to fix it?
Also, if you directly hooked up a relay to the output of the arduino and had no reverse bias diode then you must go directly to electrical engineer jail. Do not pass GO. Do not collect $200. Relays have a bad habit of having something I'd like to call "inductive kickback." You charge it up with 5V and when you quit giving it power it gets lonely and kicks you back at 100V for a couple of microseconds. It's bye bye output pin then.
2 days ago I touched the chip by notlooking where I putted my fingers (FTDI chip) and the arduino pin13 started blinking non stop even after a reset and kept on going until I got a usb cable in to reload program and now it's fine,maybe I burnt something?
Well it does not sound like you did it any favors but if you were able to save it afterwards then hopefully it'll last for a while yet. Sometimes you can damage things but not enough to totally fry it. Just enough to mess it up a bit and drastically shorten it's useful life. Things happen... That's why butterfingered people like me have 1. anti-static mats and straps 2. spares
To sum up this whole thing:
USE TRANSISTORS. If you don't know how then look it up. There's help all over the Internet. Or, if you've got some specific transistors laying around then tell us what they are and I or someone else will help you use what you have. Also, get properly rated diodes. They've got to be rated to take a reasonably large surge voltage (although with a diode in there the surge will never get anywhere near as bad as it would have been without) If you are running at 5V then 100V diodes would be fine. They're really easy to get.