Relay Problem due to the Mosfet Transistor

[faisaldj]

Hi All,

I have a relay circuit which has fourteen outputs (i.e 14 devices can be switched on or off from this) , I have attached the circuit for a single output. I am sending command to switch on the related output through the GPIO of a
microcontroller board (2.9v). Initially there was no resistance on the gate and then I had always got the output even without the input from microcontroller and after putting 10k resistance between the gate and source , my circuit was switching perfectly with the command from microcontroller but after 80 to 90 times of switching the transistor Q24 ( IRLML2402 ) does not work at all and again I always get the output without the command from the controller. After replaceing the Q24 with new transistor the circuit behaves properly and then after
some number of switching the transistor (Q24)leaves working .
Normally the drain shows 4.6v when there is no input from the controller and 0 v when there is 2.9V from the controller but when the circuit does not behave properly at that time the drain voltage is constantly 0V .

any idea?


with regards,
Muhammad Faisal.

 

[FvM]

There's no particular reason why Q24 should go bad in this circuit, and all guessing won't help, I fear.