hello,
I want to make a circuit that increases the 4.5 v from the pin of STK to 12v.
does anyone now any?

i tried one i saw with 1 transistor at this link but it doesn't work

http://www.allaboutcircuits.com/vol_3/chpt_4/6.html

 

The input voltage range of the STK500 board is 9 to 15V.

hgmjr

 

I;m not asking about this
I want to make a circuit wich will generates a relay from the voltage of an outpout pin.

 

For clarification... are you attempting to convert the 4.5V to 12V, or are you wanting to use the 4.5V to control a transistor switch in a 12V circuit? The former won't be possible, the latter simply needs the correct transistor and correct connections.

Can you post a schematic of what you've tried? And which transistor did you use?

 

That's cool, i used wrong transistors and that's the reason i had this problem.

 

Finally i tried both circuits and didn't worked . Should i try somthing else?

That i am talking about, is how i can set a relay from the voltage of STK500 pin (4.5 V)

 

What relay are you using? Will it operate from 4.5V? Will it draw more current than your STK500 can provide?