Dear All ....
I use this circuit to detect the passing steel ball, (please see photo)but when power on the IR detector gets hot and dies. So please help me to fix it . Many thank you.

 

You need a resistor between the IR detector and the base if the transistor.

 

You are applying 12V to the IR sensor output through the transistor base-emitter junction, which is likely causing the over-heating.

Does the R1k next to the transistor base connection indicate a 1kΩ resistor in series with its base?

Do you need the relay powered when the IR sensor Out signal is low or can it be on when the Out signal is high?

 

Why not use a Mosfet?

 

Why not use a Mosfet?

A P-MOSFET still requires +12V to turn-off, which may be a problem for the module.

May have to add a second buffer transistor.

 

May have to add a second buffer transistor.

The output from the module is 5 volts when no object is detected.
I suspect the 5 volt regulator is not connected correctly.
The IR transmit LED on those modules draw 37ma at 5 volts.
Use 2N7000 for Q1

Edit: Changed Q1 to 2N7000 mosfet.

 

You still need a resistor between the IR output and the base.

 

You still need a resistor between the IR output and the base.

Not really, see post #6

 

You still need a resistor between the IR output and the base.

Not really, see post #6

I think this is the schematic of the sensor (below), which uses a LM393 as noted by sghioto, that has an open-collector output:
So you would indeed need a resistor in series with the transistor base (≥20kΩ) if you want the LED to be essentially off when the output is high (LM393 output transistor off).

If you don't mind the LED being on all the time, then you don't need the resistor.

 

I think this is the schematic of the sensor

That is correct. I have one of those sensors and originally thought the LED output indicator was on pin1.
Edited schematic in post #6.

 

Is it intended that the relay be energised most of the time? or de-energised most of the time. What I see is that the IR sensor module is sinking a large amount of base current, probably exceeding the current rating.

 

Is it intended that the relay be energised most of the time? or de-energised most of the time. What I see is that the IR sensor module is sinking a large amount of base current, probably exceeding the current rating.

The relay is intended to be normally OFF.
Which circuit are you referring to?
Post #6 has the final edited schematic.