ariakovo

I want to make a ir proximity sensor that can detebreaks tct objects.For example if someone break the beam a light opens.Indoor applications.I want the distance from the emitter to the rceiver be 4m.I try many ways.First i try to make it with an ired that pulsed a frequency in 33kHz and an ir module(TSOP2233) that takes the frequency but i failed because i didn't put any data in the frequency(only the frequency with an oscillator 33kHz).I achive only 1,5m(see schem 1).I can't put data in this application!I try to put more current through the irled (600mA) but nothing.Then i try an ir photoled(see figure 2).The distance i achive was 1m.I put the photodiode in a tube with a plastic glass in front that allows to pass only ir light (870nm - 960nm).I made that because if i was going to increase the sensitivity the photodiode detects the natural light.The ir led emits in 940nm.I put a bigger resistor to increase the sensitivity but if i put a big resistor it detects natural light again with the plastic glass in front.So i decide to put a frequency again in the ired.Then i use figure 3 and i can't make it works.The photodiode has now both dc and the signal(the dv because it detects natural light and the signal.i am not sure because i don't have an osciloscope).I put a couple capacitor in series that reject the dc and i put the signal in the lm567.The frequency in the ired is 33kHz and i use a crystal for that(i am sure for the frequency).The problem is in the lm567 i can't detect this frequency.Please see the schem in figure 3(maby a wrong calculation).Are they correct because i don't have an oscilloscope rigth know and i can't go to univercity labs(we are going for exams next week).Any other idea to make it works?I have to test and phototransistors of course but i believe i can make it with a photodiode.Remote control use photodiodes.I have lose hours and hours.I am in desperate.I don't believe that it is so dificult.Thanks for your time.

untitled.GIF

The part numbers are in the schem

Conrad_Turbo

No frequency with this...



Remove the LED section and you have something you can control the gain and sense IR light.

ariakovo

The leds are ir leds or only leds(probably works like load).Whitch phototransistor?Wich nm(maybe 880nm)?And the distance.Can i achive this distance?Will the phototransistor has problems with day light or in light generaly like photodiode?

Conrad_Turbo

I am sure you could spec your own phototransistor, I wasn't too picky...I just need an IR phototransistor in a 5mm package, cost me around 35 cents for 1. Sunlight has IR light, so yes the sensor would pick it up as well.

You should put the IR sensor in a dark tube so the direct light from the LED is the only light that hits the sensor.

The distance the sensor can pick up is dependant on the output of your LED's and then adjusting the sensitivity of the IR sensor circuit.

ariakovo

The photodiode i find in the market but i can't find the phototransistor that i want in Greek market.I ask from Perkin Elmer distributor to send me some samples but the want 2 months for samples!!!!I search in stock houses for Perkin Elmer's phototransistors but i can't find.So i choose photodiode.I you have something in mind i will be glad,Thanks any way

audioguru

A photodiode can be in the photoconductive mode when it is reverse biased then it leaks current when it is exposed to light or IR radiation.

Your circuits have the photodiode forward biased so they conduct and have a voltage of 0.7V all the time.

A photodiode can also be in the photovoltaic mode when it has no bias voltage and it generates a small current similar to a solarcell.

Attached Images

photodiode circuits.PNG (20.2 KB, 23 views)

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Uncle $crooge

ariakovo

Sorry i have the diode reversed biased.I have made a mistake in the schems.

ariakovo

I put a bigger resistor and i increase the distance by 2m.The problem is that it is more sensitive in day light and when i have plenty of day light in my room the photodiode reacts with this.The R = 7.5Mhm: .How can i make it works in this distance wihtout being bothered from the day light witch has of cource ir light.If i put a frequency in the ired and take it from the receiver wiht a coupling capacitor for the dc currect which is from the continouos day light will it be correct?

audioguru

Can't you find a photodiode or photo-transistor that is in a black case that blocks visible light?

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Uncle $crooge

ronsimpson

There are three concepts I want to talk about, all involving the word “narrow”.

LEDs and photo transistors come in many types. Use the type with a narrow angle. Some send/receive light over 180 degrees. Do not use these. I am using LEDs with 10 degrees. There is much more power sent to the receiver. You must aim the devices. Lenses and reflectors help reduce the light angle. I have LEDs that put most all their power into a 20cm circle at a distance of 17meters. (using a reflector)

If you are transmitting in IR then the receiver should only see IR. That’s why some receivers come in a black case. If you can block out visible light then the receiver will see less background noise. Narrow down the range of light the receiver can see.

Normally I modulate the light with a 30khz signal like you tried first. I do not send data! I do not know why the TSOP2233 did not work. Fluorescent light has noise at 120hz and harmonics into the many khz. After you detect the light if you use several stages of 20khz hi-pass filters you will remove light from low frequency sources. Just like a radio receiver does not look for information from all frequencies but is tuned to look only at one frequency, your light receiver will be better if you only look at light modulated at 30khz. Once again narrow down the range of light you are detecting.

TSOP2233:
Look at the data sheet. It is built to respond to light at 800 to 1100 nm wavelength. (Fig 11.) Because of the IR filter over the part many kinds of light are removed.

(Fig 5) It responds to light modulated with a tone and rejects light with out a tone. (33khz)
(Fig12) It has a 55 degree angle. If you can reduce that it will be better. Long black tube, lens, reflector etc.

Last thought. The TSOP2233 should work but maybe you are right it needs “data”. By adding a simple ripple counter like the MC4060 (4020 or 4040) to your transmitter you can make a signal much like the TSOP2233 was built to receive. I would try to send 64 cycles of the 33khz then not send the next (64*3) cycles. If you read “Suitable Data Formats” they talk about sending 10 to 70 cycles then waiting for 4 times that time before sending again. If you take a ripple counter and OR together the 32khz output, the divide by 128 and then divide by 256 output, you will get a 33khz signal that is on for 64 cycles out of 256. (if I did the math correct)

(edited to say HI-PASS not LOW-PASS)

ariakovo

The photodiode i use is a black covered photodiode that rejects visible light but the day light has also infra red radiation.So i will use narrow angle to reduce this problem.Any other ideas for increasing the distance?

ariakovo

You have right with the way i can transmit to the TSOP2233.I read the data formats.But ibelieve that with a phototransistor with narrow angle will make it works.I have problems wiht photodiode because it wants a IC with 0.01pA input because the photodiode has 47nA when the see ir radiation.With a phototransistor i will have no problems because phototransistors produce 1 to 12 mA current when they see ir light.So i will use it direct.About the frequency i don't understand why to use a low pass frequency.If i use a low pass frequency i will get also the ir light(DC or very low frequencies).So maybe a high pass or better a band pass.Will i make it works with the lm567 witch i believe that i can make it works both like a band pass filter and a frequency detector.In the end another question.If phototransistor detects the visible light (althought the black tube and a glass that allow only the ir radiation pass) can i reject the dc or lower frequencies with a caplling capacitor and then to take the frequency or the frequency will never be detected.Thanks for your time.

audioguru

The TSOP IR receiver is used in many TVs. They have a range of 10m to 15m.
Modulate your IR transmitter like the TSOP datasheet says to do and it will work fine.
If you try to make your own IR receiver then it will have many parts and it won't work as well as a TSOP IC.

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Uncle $crooge

ariakovo

I see but i have to use a phototransistor because i can't put in there the components for make the data format that vishay says.Also i have to make it on my own because i want more experience.I have found some phototransistors in Greek market and i also have found soe of them in the Belgium (stock house) from Perkin Elmer.But i am a bit concernend about the frequency i have to detect in the receiver.Do you think that with the lm567 i will have the bandpass fillter and the frequency detector i want?Thanks anyway

audioguru

All you must do for the TSOP IR receiver to be very sensitive is to make a slow oscillator with one Schmitt-trigger gate, a resistor and a capacitor drive a faster oscillator with a Schmitt-trigger gate, a resistor and a capacitor oscillator. Then it is bursts of data.

The TSOP has an IR photodiode in a black case that blocks visible light, a high gain preamp with AGC, a pretuned bandpass filter and an output transistor.
I wouldn't use an old LM567.

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Uncle $crooge