ive tried my TSOP1738 receiver.
TSOP1738 gives me an increase of about 10cm...which is a total of 45 cm only.
I am using a high power transmitter operating at 100mA(its max rating) at 38khz.
i am wondering how can I boost the distance up to 20feet?Anyone can help me in this?i even tried boosting the transmitter to 200mA and the distance remains the same...
I wonder how does TV remote control boost its IR signals that it will be able to detect it even those its not aligned to line-of-sight, and with a long range?

i removed one of my TV remote and used its IR emitter,however it gives me the same detection range..

can anyone suggest me a long range circuit?thanks

 

Panadol,
You forgot to attach the schematics of your IR transmitter and your IR receiver so we can see what you are talking about and if they are designed correctly.
Are you transmitting bursts of data?

You mentioned "reflection technique". Please explain.
I can point my TV's remote at the shiny white wall about 2m behind me at night and it controls my TV about 5m in front of me.

__________________
Uncle $crooge

 

my circuit is fairly simple
i used a normal 555 timer circuit with R1=6900,R2=5100 and C=2nF to get it working at 37.88khz. I tried different currents for the emitter, 90~100mA, and also up to 200mA but the distance remain the same.
I am not sending a burst of data and i dun that.

all i need is just to sense an obstable 10 feet away. that is why i said i need a reflection technique which the total is 20 feet.(isit called duppler effect?).
My TV remote and sense more than 5m too,but i dun noe how to make my circuit to be a able to sense around 20 feet which is around 7-10m..... i wonder how those remote control works too...

Attached Images

	receiver.JPG (12.3 KB, 46 views)
	transmitter.JPG (13.1 KB, 53 views)

 

Well you don't have a series resistor on the LED, so it's rather nasty to both the 555 and the LED!. To increase range you need to use a driver transistor to increase the power to the LED - it's usual to pulse than at about 1A or so, but ONLY with a very low duty cycle - this easily gives about 30-40 feet range.

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ooh...means that i have to amplify the current from the pin3 of the 555 upto almost 1A?im not very good in transistor and current amplifying cicuit,thats why i avoid,using it...can suggest or show me any circuit?
if its like that, i will have to re-adjust my R1 and R2 values, is 10% duty ratio ok?at 38khz?but the max ratings of the transmitter is 100mA......just afraid it will blew up the LED....btw, what is the current supplied to tv remote controls(powered by only 3V, can it reach 1A?)?
thank you very much

 

Your 555 circuit doesn't have a supply bypass capacitor to supply high current to the 555 and to the IR LED. Maybe that is why they didn't burn out without a current-limiting resistor.

If you don't send bursts of data like the datasheet says to do then the AGC in the TSOP reduces its gain. Then its range will be short.

Are you trying to sense a reflection from an object that is shiny and white or from a mirror that reflects perfectly? Then it will work.
If you are trying to sense anything else then you need a camera or something different.

__________________
Uncle $crooge

 

Check my PIC tutorials, the IR hardware shows how to connect the IR receiver and the IR LED - you could use the same LED driver with your 555.

TV remotes commonly pulse at 1A or higher, they rely on a good sized electrolytic to provide the high current pulses, and short bursts of IR - with plenty of time for the capacitor to recharge in between them (my IR tutorial does the same).

Basically a TV remote sends coded pulses, then a completely blank period, then repeats again - this means the IR LED has time to cool down between data streams.

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audioguru,
yes, i am trying to sense from a shiny surface whihc is 10 feet away.and my transmitter and receiver is placed at the same place.what is a bypass capacitor?and where to place it to supply high current?quite blur with that method to boost current
thank you very much

nigel goodwin,
i will try to pump it up to 1A and see whats the result, but i have to use a very short duty ratio right?what is the high voltage of RB1 in your tutorial?what is the alternative besides BC337?
sorry to give u guys so much trouble just becuase i suck at it...
i'll try doing it and let u guys know the result.thanks.
thnk you vry much too

 

A bypass capacitor of about 100uF should be connected across the power supply to provide the high current for the 555 and for the IR LED.

Are you sending bursts of IR pulses?

__________________
Uncle $crooge

 

hhmm..ok..but how high will the current be?i will test it out.later...
i am just sending a square wave which is tuned to 38khz, its that consider burst of pulses?and my current duty ratio is aobut 50%.
my whole motive is just to sense something infront 10feet away, hence i dont need any modulation technique for my microcontroller to dingtinguish between different signals. all i want is transmitter send detect an obstacle 10 feet away, and then reflect back to the recevier which is at the same plane of the transmitter..hope i made it clear :P

i am curious how remote control are tuned.the IR emitter in remote control are just ordinary ones,but how they made it that it can be sense at all directions even not pointing directly to the tv?(if im not wrong, IR in remote contorl is narrowbeam...)
THANK YOU SO MUCH!!ALL OF YOU!

 

If you modulate the IR LED with 1A pulses then the transistor driving it conducts 1A through it and 1A comes from the bypass capacitor across the supply.

You are sending continuous pulses without pauses, so the TSOP thinks it is interference and it turns down the gain. Read again what I said about sending bursts of pulses:
"The TSOP seres of IR receiver ICs are designed for remote control of TVs and other entertainment products. Data is sent in bursts of IR pulses and the automatic gain control in the receiver IC uses the breaks between bursts to know it is data and is not continuous interference. If it receives continuous pulses then it reduces its gain, thinking that the continuous pulses are interference from a compact fluorescent bulb or other item that continuously pulses IR at 38kHz.

The data burst consists of a start bit, the command code bits (volume up or down, channel number etc) then a device code (TV, DVD player, CD player etc). Then a pause between that burst of pulses before the burst of pulses is repeated again if the button is still held down.

The TSOP receivers have an automatic gain control that reduces the gain during a continuous signal, because it thinks it is interference. Therefore the data must be received in bursts of from 10 to 140 data pulses then a gap time of at least 14 pulses between bursts for its gain to continue at max."

You can buy them with a narrow beam or a wide beam or anything in between. They use a medium wide beam.

__________________
Uncle $crooge

 

Yes i got it working at more than 20 feets already.I tested its functionalty by tapping the output of TSOP1738 into a digital scope. When it detected an IR, it will have a pulse drop till 0 volts.The pulse is very short.
However it is true that the maximum gain of it is actually at a burst of short pulses. I did this test with a tv remote and realized that it can detect at even at very very far distance. However the receiver will only detect the IR from my transmitter if i continously on-off the transmitter, so that the pulses will be bursty.

since i using duppler effect(reflection)I think i will use a narrow beam IR for
my transmitter for accuracy and better reflection.

What component or what can we do do make the pulses to be bursty? can aynone help me in this?thanks

 

Not doppler, doppler isn't reflection, it's the change in frequency caused by the reflection from a moving object - towards you increases the frequency, away decreases the frequency.

A simple way is to use a PIC to generate bursts of IR, you can even use the same PIC to receive IR as well.

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oh ok...
i dun get it by using a PIC to generate a burst of IR, how?.i was thinking to use a PIC to send PWM signals to the 555(as VCC), so that it will on and off( PWM period has to be longer than 26us(38khz) ). So that there will not be any continuous signal sent to the receiver.

 

It's trivial to generate 38KHz in software with a PIC, check my IR tutorial!.

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