plz help me: IR remote control & receiver range problem

[afti_khan]

dear.......,

i'm student of final year electrical engineering. i'm working on my final year project but theres some problem.
my project is depicted as under:

a keypad is interfaced with the 8051 uC port-1. with the TXD pin of the uC i've connected the reset pin of the 555 timer & the timer is configured for 38kHz square wave.On the output pin of the 555 i've placed an IR LED with a 15ohm resister( the 555 is getting Vcc=5V).
The receiver module which i'm using is TSOP1738. The output of the TSOP1738 is given to RXD pin of 8051 uC. on receiving a valid 8 bit code the controller on the receiver side complements a bit on port-1.
The problem is that the range of my project is very low. what should I do?
plz help me as soon as possible bcz my project submission date is approaching

i'll be very thnkful to u

 

[Gorgon]

Hi,
Since I don't know your output config, I would assume that the IR diode does not get enough drive current. What is the Vf of the diode? Are you sinking or sourcing the LED?
The 555 sink better than source at 5V.

One think you could do is to add a transistor for the LED drive, But you need to be careful not to drive it at reset.

If you have a scope you could measure the voltage over the 15 ohm resistor, and calculate the current.


TOK

 

[david90]

Re: plz help me: IR remote control & receiver range prob

what kind of range r u aiming for? U can increase the range by increasing the power of the infrared LED or u can amplifier the signal coming into your receiver. I'm currently working on a similar project and i'm using an op amp to amplify the infrared signal.

 

[usernam]

Try using the TSOP 1838. Better detection and its less susceptible to noise. So the range should increase though maybe not by too much.

 

[artem]

Is 555 configured to provide 50 percent duty square pulses ?

Put schematics here as your description is not clear enough .

 

[afti_khan]

Re: plz help me: IR remote control & receiver range prob

yes it's configured for 38kHz. the circuits(the at89c51 ckts not included) are given
plz help me improving the range. it's very very low(round abt a few inches)

 

[afti_khan]

plz help me . my project submission date is coming

 

[VVV]

Re: plz help me: IR remote control & receiver range prob

Normal IR remote controls pulse the LED at 1~2A. That is right, amperes. Thus, for a 5V supply you need about a 3 ohm resistor in series with the LED. Use a transistor that can give you that peak current, either MOSFET or bipolar.

If that still does not solve the problem, use two or more LED's, each with its own series resistor and drive them all at the same time.

If you have a higher voltage available, such as 12V, you can connect the LED's in series and calculate the resistor for about 1A peak, assuming about 2V across each LED. Say you have 4LED's, that is 8V, then you need a 4 ohm resitor in series with them. You can use 3.3 ohm, since the transistor will have some voltage drop across it, too, especially at 1A.

Use a fairly large cap (100-200uF) right across the LED driving circuit, to eliminate the spike sdue to this large current.

Of course, the LED's must not be driven continuously, but in short bursts. The micro should take care of that, stopping the 555, or better yet using an AND gate to disable the signal that drives the transistor. So you feed the output of the 555 to one input of the gate and the other input will be controlled by the micro.

With such high currents and more than one LED, you are very likely to get your range.

Do you think the receiver is OK?
Try it with your TV remote control for range. If that does not give you the correct range, then possibly the receiver is not good enough, either. Of course, you need a scope to look at the output signal, since the micro cannot recognize it.

 

[artem]

did you match LED to TSOP1738. It should 950 nm wave LED. Can you confirm that?

Did you check by scope signals at TSOP1738 and LED?

 

[ankushgupta]

plz help me: interfacing of tsop 1738 with 8051

dear friends
i am working on a project,which uses tsop1738 to detect whether there is an intrruption in the path of IR ray.i want to connect tsop with 8051 some how so that 8051 can count the interruption per second.(i will use the timer 0 of 8051 as an event counter and timer 1 to generate an interrupt every second)
the problem is that i don't know the exactly about the output of tsop.
could anyone post the output waveform and circuit to interface tsop with 8051.