The uC is a Modtronix SBC68EC.
I noticed something strange lastnight that could also be the cause of the issue. I basically rebuilt the circuit on a breadboard so I could easily change out the components etc, and when the uC pin is not active, it is actually grounded... I put a multimeter between an 'on' pin and an 'off' pin and got a reading of 4.98v which I would not have expected unless the 'off' pin was grounded.
How I stumbled upon this was I found was the relay was actually engaging when the power was applied to the circuit, and disengaged when I removed the uC pin from the board. I checked and rechecked the wiring of the circuit, which was all ok, and thought it may have been a slight voltage as suggested by Pencil, however after testing with the multimeter between the pins I wasn't so sure, and then found putting a diode in line with the uC and resistor stopped this from occurring and everything was working normally.
In the process of all this, I used a new BC549 and used the 1N4148 diodes as suggested.
So I think it may have been the constant current passing from the C to the B pins on the transistor that was "burning it out".
I will monitor now and see how it goes, but does my above testing shine any further light on the issue for you guys?
I noticed something strange lastnight that could also be the cause of the issue. I basically rebuilt the circuit on a breadboard so I could easily change out the components etc, and when the uC pin is not active, it is actually grounded... I put a multimeter between an 'on' pin and an 'off' pin and got a reading of 4.98v which I would not have expected unless the 'off' pin was grounded.
How I stumbled upon this was I found was the relay was actually engaging when the power was applied to the circuit, and disengaged when I removed the uC pin from the board. I checked and rechecked the wiring of the circuit, which was all ok, and thought it may have been a slight voltage as suggested by Pencil, however after testing with the multimeter between the pins I wasn't so sure, and then found putting a diode in line with the uC and resistor stopped this from occurring and everything was working normally.
In the process of all this, I used a new BC549 and used the 1N4148 diodes as suggested.
So I think it may have been the constant current passing from the C to the B pins on the transistor that was "burning it out".
I will monitor now and see how it goes, but does my above testing shine any further light on the issue for you guys?