need of long range IR transmiter

[audioguru]

hhmm..ok..but how high will the current be?

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.

i am just sending a square wave which is tuned to 38khz, its that consider burst of pulses?

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."

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...)

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

 

[panadol]

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

 

[Nigel Goodwin]

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

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.

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

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.

 

[panadol]

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.

 

[Nigel Goodwin]

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!.

 

[panadol]

ok, btw, to im not good in PIC, hence i am using 2 555 to limit the pulses....
does anyone know of any IR module that are active high and receives continuous pulse?
the only one i found is SFH 5510-38.but its not available in my place/area.

 

[captnstoed]

I am looking to build this circuit for similar reasons. I need to know how to pulse the ir without the use of the pic, or is that the only way? I need only to send a beam of ir energy (10-20 feet) that, when broken, pulses a signal relay.
Also, could a laser be pulsed at a freq. that a reciever would "see" and reduce interference?

 

[audioguru]

We were talking about using a TSOPxxx IR receiver IC and an IR transmitter made with two oscillators. One oscillator is at 38kHz and the other oscillator causes the 38kHz to be in bursts. Two 555 oscillators can do it easily.
Most TV remotes use this method and the range is at least 10m.

You are talking about using a laser which is not IR and which probably won't be received very well by an IR receiver IC.

 

[HarveyH42]

We were talking about using a TSOPxxx IR receiver IC and an IR transmitter made with two oscillators. One oscillator is at 38kHz and the other oscillator causes the 38kHz to be in bursts. Two 555 oscillators can do it easily.
Most TV remotes use this method and the range is at least 10m.

You are talking about using a laser which is not IR and which probably won't be received very well by an IR receiver IC.

Oddly enough, I did a similar experiment earlier today. I made an IR proximity alarm (first microcontroller project). I get about foot range, but it triggers every time I use a remote control. So, I wired up a laser pointer on the breadboard I used to develope the project, in place of the IR emitter. It triggered the PCB version. Took everything outside, set the alarm on the back fence, triggered it from my porch about 60 feet away.

Point of the experiment was to see if the IR module would work from a laser pointer, laser trip-wire project I've been thinking about. Need to wire something up and see if the module can handle continous 38kHz pulses, as I have had no luck turning it on and off in my program (want to reduce battery consumption...).

 

[captnstoed]

I see ..... what freq. should the second oscillator be tuned to? I am getting my order together.

Harvey, what type of reciever was it that you used? Was it an IR or ?
Did you try it in the sun or shade?

 

[audioguru]

what freq. should the second oscillator be tuned to?

The datasheet says 1400Hz max, but if your square-wave isn't square then use a lower frequency maybe 500Hz. This second oscillator should gate the 38kHz by connecting its output to a voltage divider at the reset pin of the 38kHz oscillator.

 

[HarveyH42]

I see ..... what freq. should the second oscillator be tuned to? I am getting my order together.

Harvey, what type of reciever was it that you used? Was it an IR or ?
Did you try it in the sun or shade?

Its an IR module, and the sun was just starting to rise, so mostly dark. Can't see a laser pointer very far in daylight.

 

[captnstoed]

I have a laser that you get at one of those "chain stores that sell everything" and I can see it well in the day light. The neighbors house is easily 60-75 feet away and I can see is against their outside wall. You do need some kind of large flat surface to locate it and aiming is tough at that distance.
What about modulating both the laser and the IR led? The laser would be useful to aim with.
Im going to try that with mine. Im waiting on parts now anyway!

 

[HarveyH42]

You can pulse the laser at 38 kHz and it will trigger the IR-Reciever-Module directly. The laser isn't as bright at 38 kHz, it's only on half the time. I did run the output from the MCU through a transistor to see if higher current would help, but its been kind wet and rainy lately. Does seem slightly brighter, but not as much as I hoped.

 

[audioguru]

The case of a TSOP1738 IR receiver IC is black and blocks visible light very well. I know a red laser is very bright but look at this graph and try to determine how little of the red light will be detected.

 

[HarveyH42]

Don't have a part number on the reciever module, but it works. Having a rainy chrismas, figured I'd mess with it a little further. Wanted to bounce the laser off a mirror, total pain in the ass to line up that way. Have to figure out something. Had some camera mounts with ball swivels, but no idea where I put them...

 

[mvs sarma]

Hi HarvyH42,

To incerase the range, i understand that we have to tune the IR TX (555 frequency to be close ly equal to to IR Rx and only then the range will increase,

Reg arranging mirrors, i feel it may be possible by first looking with a red Laser torch (used as pointer in presentations.) you may perhaps initially arrange mirrors by using stick gum from your hall to another room and to a third room from there.

After being able to align with red laser troch and the final point can be substtuted with TSOP Rx and the torch by IR Tx perhaps, sir

Also, you may be able to park your car away and use its View finder mirror to reflect the signal back. of course you have to temporarily substitute by sticker , a flat mirror across it and orient it to reflect you signal back to a wanted point. however a visible red laser light is purposeful, sir

regards

 

[HarveyH42]

It was just quick experiment to see whar kind of distance. Didn't really think lining up a tiny dot on a small target would be such a pain. Need to make something that will do very fine adjustments and not move around. Got a few ideas with a ball joint, couple of screws and springs. Just no spare time to build lately. Hopefully after the holidays.

 

[Nigel Goodwin]

It was just quick experiment to see whar kind of distance. Didn't really think lining up a tiny dot on a small target would be such a pain. Need to make something that will do very fine adjustments and not move around. Got a few ideas with a ball joint, couple of screws and springs. Just no spare time to build lately. Hopefully after the holidays.

A little advise - think BIG, think STRONG, think HEAVY - it mustn't move at all!, and the greater the distance the more solid it must be.

 

[captnstoed]

Ive got the tsop32238 pn the bread board. Can I plug it into a comparator to get it to energize a small signal relay or will it have to go through a pic? I tried a transistor with no luck.