IR Reciever Delayed Trigger

[Suraj143]

Can somebody help me to add a RC network to this circuit to make this circuit to activate delayed.

In other words I'm focusing an IR transmitter to this receiver, when somebody crossed the beam this relay will triggered.The problem is I want to turn on this relay after a small amount of time like 1 second etc...........

 

[MikeMl]

There is a lot wrong with your circuit.

First, get rid of the 330Ω resistor. It just degrades the voltage regulation for the TSOP.

Second, the TSOP can only sink 0.5mA, which is not sufficient to drive the PNP base. When the output of the TSOP is high, the output voltage can go no higher than 5.5V, so the PNP is always partially on (not good).

Now, when you say you want a 1 second delay, do you mean that the beam must be broken for 1 second before the relay pulls-in?

Or do you want the TSOP to detect a very short break in the IR beam, and then delay the relay pull-in 1 second after the short break? If the latter, how long should the relay be pulled-in before it drops-out?

 

[Suraj143]

Hi Mike some very good points.

What I need is when somebody breaks the beam it must delayed turn ON the relay.That means beam must broken for 1 second time before the relay pulls-in.

Ex:cross the beam--->delay--->activate the relay

How can I drive the relay from TSOP?

 

[MikeMl]

Using an IR remote control receiver like the TSOP as a beam-break detector is not exactly what it is designed to do. It works, but with the following limitation:

The TSOP has an Automatic Gain Control in its 40Khz receiver. When you shine a continuous 40 Khz IR beam on it, the AGC loop adjusts itself for the prevailing signal level. It is very sensitive to a momentary reduction in the 40Khz IR carrier; but if the interruption lasts too long (more than about 1 second), the AGC loop begins to readjust itself, and as it does, the output of the TSOP returns to the inactive (high) state. When the TSOP is being used to receive the IR pulse code, none of the interruptions in the IR carrier last more than a few ms, so the AGC loop time constant has a problem following long interruptions....

You will need to test how long the output of the TSOP stays low when you block the IR beam. If it goes back high (even thought the beam is still blocked) in less than a second, then your 1 second delay to pull-in the relay will require a triggerable one-shot like a 555. A one-shot triggered on the low-to-high transition would work to drive your relay, too.

If the output of the TSOP stays low for 2 or 3 sec while the beam is blocked for longer, then you would need a one-shot triggered on the high to low transition of the TSOP output which has a 1 sec period, and the relay would be pull-in while (TSOP low) AND (one-shot LOW).