IR receiver Not Working as expected.

[deadly123]

Dear all,
I look forwad for your help on this.

I have tried using a 555 T imer IC to generate 38 Khz pulses to drive an Ir led. But the problem is that the TSOP 1838 receiver IC is not responding to the pulses. I made sure that 38 Khz pulses are being delivered and a LED connected to the Output of receiver IC flickrs when I use a TV remote.

I couldn't figure out what might be problem? I kind of think that the receiver IC is neglecting the 38Khz pulses from 555 as they are continuous? But I don't know what might be the solution??

 

[3v0]

I kind of think that the receiver IC is neglecting the 38Khz pulses from 555 as they are continuous?

That should be the problem. You need to send pulses of the 38KHz carrier. A continuous stream is ignored.

 

[deadly123]

That should be the problem. You need to send pulses of the 38KHz carrier. A continuous stream is ignored.

Thanks 3v0
Ya I understand that. I read that on the data sheet of TSOP 1838. But I didn't get the idea to make the receiver work.
Can you help me on this.

 

[Mikebits]

First, are you sure your 555 is actually operating at 38Khz? The 1838 has a bandpass filter so you need the 555 to be close to 38k.

Second, according to the 1838 data sheet, it will not respond to a continuous stream.

From data sheet

The distinguishing mark between data signal ( not
suppressed) and disturbance signal (supressed) are
carrier frequency, burst length and Signal Gap Time
(see diagram below).
The data signal should fullfill the following condition:
• Carrier frequency should be close to center frequency
of the bandpass (e.g. 38kHz).
• Burst length should be 6 cycles/burst or longer.
• After each burst a gap time of at least 9 cycles is
neccessary.
• The data format should not make a continuous
signal transmission. There must be a Signal Gap Time
(longer than 15ms) at least each 90ms

https://www.electro-tech-online.com/custompdfs/2010/10/tsop1836.pdf

 

[deadly123]

ya, I am sure that 555 is generating 38khz pulses.

"• Carrier frequency should be close to center frequency
of the bandpass (e.g. 38kHz).
• Burst length should be 6 cycles/burst or longer.
• After each burst a gap time of at least 9 cycles is
neccessary.
• The data format should not make a continuous
signal transmission. There must be a Signal Gap Time
(longer than 15ms) at least each 90ms."

So I need to put a delay of at least 9 cycles in between each pulse. Is that what you are trying to say??

 

[3v0]

It is the transmitter end you need to work on.

Use a AND gate after the 555. One input is the from the 555, use the other input to generate pulses where 1's are a burst of 38KHz signal.

Even if you just want to use the setup to detect broken beam you still need to follow the rules or the TSOP will ignore you signal.

 

[MikeMl]

I have not tried a TSOPxxxx, but the Sharp GP1U58X IR detector works great as a beam-break detector with a continuous 38Khz modulated IR beam, with no other other modulation on the beam other than just blocking the beam with your hand or other object. With a continuous 38kHz signal (or no IR signal) the receiver output is high.

When the continuous 38kHz IR signal is blocked by sweeping an opaque object through the beam, the waveforms below show what happens. The reappearance of the beam after momentary interruption causes the output pin of the receiver to go low and then back high again with a duration of about 60ms. This duration is independent of how long the beam is interrupted, as long as the interruption is at least a few ms.

I have used this outside in daylight, and got a range of ~3m. I have used this to detect a runner on a forest trail.

 

[3v0]

Sounds like the Sharp would be a bit easier to use for detection application.