Help needed trying to find out

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.

Many Thanks & Best regards


Can you pose a schematic?

hi sorry please see attached photo

Please explain the intended operation.
There are three components whose functions need simple explanations:

  1. What does the IR LED receive and what is supposed to happen when it receives?

  2. What is expected to happen when you push the momentary trigger?

  3. What is the purpose of the relay? Usually a relay has two wires that energize a coil and switches the connection state of 2 or 3 wires or a multiple thereof. Here I only see what I currently assume is the coil connection.

Please help us understand the function better.

  1. The PNP transistor is upside down.
  2. The position of the resistor is different.
    For BJT, the base current must be limited.
    (Your drawing position is case for MOSFET.)

OP needs a switch there, not an amp, makes sense, but my concern is how is the IR supposed to trigger this. Is there supposed to be a code received or is it supposed to switch on with every pulse of IR received?

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