Icne555 cofig. Prob.

Thread Starter

sammmm

Joined Apr 5, 2014
7
please help me
this circuit is not working prperly
the output at pin 3 is not getting high when input at pin2 is getting low
ICNE555 is configured in monostable mode.
 

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nerdegutta

Joined Dec 15, 2009
2,676
please help me
this circuit is not working prperly
the output at pin 3 is not getting high when input at pin2 is getting low
ICNE555 is configured in monostable mode.
Hi, Sammmm.

Explain what you expect the circuit to to. Are you expecting the relay to be energized when the IR sensor is not receiving IR?

Explain the whole setup.
 

THE_RB

Joined Feb 11, 2008
5,438
Pin 2 won't get low!

The 3-pin IR sensor has an open-collector output pin, that pulls LO when IR is present. Your diode stops it from being able to pull pin 2 low.

Also, since the pin is open-collector it cannot source a + voltage, so you need a pullup resistor from the IR output pin to +5v. 10k should be fine but some IR modules need a high value like 27k.
:)
 

Thread Starter

sammmm

Joined Apr 5, 2014
7
hieee nerdegutta,
this is the circuit diagram of automatic tap
in which we have used TSOP1738 IR sensor whose output get low when the IR RAYS falling on it get interrupted.
and this is connected to IC555 PIN2 which is configured in monostable mode. the output of this IC GET higher when trigger at pin 2 get lower .
this is the whole procedure to energise relay but this is not happening really
can u help me to detect the problem????
 

Thread Starter

sammmm

Joined Apr 5, 2014
7
Pin 2 won't get low!

The 3-pin IR sensor has an open-collector output pin, that pulls LO when IR is present. Your diode stops it from being able to pull pin 2 low.

Also, since the pin is open-collector it cannot source a + voltage, so you need a pullup resistor from the IR output pin to +5v. 10k should be fine but some IR modules need a high value like 27k.
:)
I can't understand wht are u exactly trying to saying

can u please elaborate????
 

Thread Starter

sammmm

Joined Apr 5, 2014
7
yes I have read it but there is no problem in the sensor
the whole problem is about ic555 which I think not config properly
 

SgtWookie

Joined Jul 17, 2007
22,221
You don't have a diode across the relay coil. Without a diode there, the current from the relay coil won't have a place to go when the transistor turns OFF, and the transistor will be destroyed due to the high voltage pulse. Connect a diode across the coil, with the cathode (band) towards the normally more positive side of the coil.
 

Thread Starter

sammmm

Joined Apr 5, 2014
7
Pin 2 won't get low!

The 3-pin IR sensor has an open-collector output pin, that pulls LO when IR is present. Your diode stops it from being able to pull pin 2 low.

Also, since the pin is open-collector it cannot source a + voltage, so you need a pullup resistor from the IR output pin to +5v. 10k should be fine but some IR modules need a high value like 27k.
:)
Hey , THE_RB
I have tried what you said. And it works but there is another problem. The relay connected in this circuit requires 7A,6v parameters which is not possible in this circuit as it works on 5mA current . Can u suggest me how to drive relay without affecting current circuit .
 

THE_RB

Joined Feb 11, 2008
5,438
If your circuit runs from a PSU that only has enough power to run the 555 timer, then to drive the relay you need another power source. One that has enough power to drive the relay coil.

What other power sources do you have?

You need to provide more information, like an "overview" of the entire project, not just the 555 circuit.
 
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