IR remote control relay help

Thread Starter

HaseebEngineer

Joined Aug 8, 2013
22
I have succesfuly made a circuit and its working but whenever i plug in the circuit the relay turn on automatically without even pressing the remote button. I dont know whats wrong with the circuit.
 

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ScottWang

Joined Aug 23, 2012
7,501
You need a power up reset and another npn driver for LED, it means that you should adding another 4.7K and NPN to drive the 470 resistor and LED, why you should do that, because the output current is too less from Pin 2.

Or you can try to moving 470 and LED to in parallel with the coil of relay, it will save the 4.7K and NPN bjt..
 
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ScottWang

Joined Aug 23, 2012
7,501
The power up reset as:
In series with a 47K/0.25w resistor between Pin 4 and Pin 15, and connecting a 0.1uf capacitor from Pin 15 to +6V.
 

Thread Starter

HaseebEngineer

Joined Aug 8, 2013
22
Actually the problem is not with the led ... its with the realy ... When i completely turn off the circuit and then turn it back on, the relay automatically turns on and the bulb connected to it turns on ...
 

Kermit2

Joined Feb 5, 2010
4,162


Where is the relay? I see what appears to be a transformer in the upper right?

Is that supposed to be the relay? If that is the relay, which contact is moveable, which contacts are the NO/NC ones?
 

Thread Starter

HaseebEngineer

Joined Aug 8, 2013
22
I did what u said but still not working properly ... Still when i turn off and then on the circuit the relay turn on and then i have to turn it off with remote ...
 

Kermit2

Joined Feb 5, 2010
4,162
Try adding a small capacitance to the collector of the relay driver. Might be power on transients. 1 uf would be enough to see if that is the defect.
Try it on the +6 volt power side of your relay coil first.
 

Alec_t

Joined Sep 17, 2013
15,119
You should have a back-emf suppression diode (reverse-polarised) across the relay coil to protect the transistor. Also, a 0.1uF ceramic cap should be connected directly between the supply pins of the IC to decouple it.
What is the purpose of the 10uF cap? It will slow down the edges of the clock pulse and could make the clocking unreliable.
Your LED would be better driven from the transistor collector rather than from the IC (which has very limited output current sourcing capability).
 

tubeguy

Joined Nov 3, 2012
1,157
no, its a relay ... and the pin to which the bulb is connected is the NC one ...
The N/C contact will energize the bulb with the relay Off.
So, it is likely the bulb will light up on power-up.

To clarify, when you say the relay is On at power-up, is the LED connected to the output (pin 2) also On at this time?
 
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