I am a beginner in electronics.I tried to make a circuit using ir reciever and bc547 in which motor runs when a remote pointed on reciever,but motor always run .Help please.Thanks for reading my query.

 

Can you sketch us a schematic, otherwise we'd just be guessing.
What IR receiver and what motor are you using?

 

You will need to post the schematic and the part number of the IR receiver. You will also need to give information on the remote including details of how the IR beam is encoded. (Assuming it is encoded.) To have any chance of solving your problem we need to know what you have built.

Les.

 

Can you sketch us a schematic, otherwise we'd just be guessing.
What IR receiver and what motor are you using?

Sorry i couldnt identify which ir reciever it is.It has a marking LFN on top(upper side),Can you help me identify the reciever?I'm still trying to identify its pinouts.I have uploaded the schematic sketch.

 

What voltage are you running it on?

 

The BC547 turns on when its base has positive current through the base resistor.
You probably have a VS838 Chinese IR receiver. It produces an output to ground when it receives bursts of IR, and a positive output with no IR. That is backwards to what you want.

Then you need a PNP transistor with its emitter connected to the positive supply and the motor connected between its collector and ground. A BC557 is the PNP version of a BC547 NPN transistor. Both have a maximum allowed collector current of only 100mA but your motor might draw much more current which will quickly burn out the transistor.

A burned out transistor will either make the motor run all the time or prevent it from running.
The motor will probably produce high voltages which will also damage the transistor. The high voltage is prevented by connecting a diode across the motor with the correct polarity. The wrong polarity will cause the transistor to burn out.

 

What voltage are you running it on?

4v

 

It's a difficult and not-very-productive game to try to build circuits when you don't know what actual parts you have.
There are many ways you could connect the device, only one will work, several others will destroy the part.

If you want to scrounge IR receivers from existing junk, it's best to study how the parts are connected on the PCB, find the ground pin first using a continuity tester.
Then find the Power pin, finally the output, which usually goes straight to the MCU chip. If you can, power the board and measure the voltage on the power pin.

Carefully draw a diagram, then remove the part.

Keep in mind that the output from these devices is a train of narrow pulses, the motor might not move in response, due to the limited 'on-time' of the pulse train.
Also note that the receivers are designed for different carrier frequencies- try to use the original remote, otherwise it might not respond to the IR signals at all.

 

IR bases on 567 tablet, not a transistor. BC is only a switch.

 

In post #4 Amal said the IR receiver has LFN on top. Google shows an LFN VS838 IR receiver that is similar to TSOP1838 European IR receivers: