Relay and MOSFET help

[madmikejt12]

hi, i have designed a circuit on chrocodile technology and everything works apart from when i press one of the 'set' switches, the MOSFET blows up and it says something about the drain voltage

any ideas?

same thing happens when using a transistor
here is what i have done:
https://i14.photobucket.com/albums/a316/madmikejt12/eto/untitled5.jpg

it is the MOSFET on the end of the 1st part of the circuit (under the relay coil) that blows up

 

[Dr.EM]

6v should be fine, so i'm assuming its the lack of a protection diode on the relay coil? When the relay turns off, the inductance of the coil creates a brief high voltage spike which can damage both transistors and MOSFET's. Look here to see an example of how to use the protection diode:



Its rather an unusual symbol for a MOSFET too? Not the one i'm familiar with.

 

[madmikejt12]

of course.. that did the trick

Thanks alot

**broken link removed** is that something like the symbol you are used to?

 

[Dr.EM]

Yep, thats the one I use; not always with the circle, but broken lines at least.

 

[madmikejt12]

yeh...

Thanks for your help anyway.

all i need now is:
Front door opend--->6 second time delay---> if code not entered alarm goes off, if it is entered, alarm is de activated

put them both together, and then my alarm is complete