I’m trying to resolve a problem with this latch and release break beam circuit

[Barbados1993]

Help Needed!!

I’m trying to resolve a problem with this latch and release break beam circuit – with PNP transistor amplifier It works fine for a few minutes then consistently breaks down – as though the transistor is getting overheated?

It works again after about 20 mins.. It’s driving me nuts!

I’m not very clued up on transistor selection.. and mainly using what’s been available in a liitle selection pack.. then I have pages of scrawling’s which have lead me to arrive at resistor values – I’ve tried lots of transistors and different resistors but any combination which works still seems to fade away after repeated use.

It was suggested that I add a flyback diode – which I tried (in blue) this made no difference

Any help or advice greatly appreciated.

 

[rjenkinsgb]

The transistor is connected backwards.
A PNP needs the emitter to positive & collector to negative. Swap the emitter and collector leads.

Not knowing what is driving it, ut coudl also be damaged by excess base current, if the input/base is connected directly to 0V rather than via a current limiting resistor.