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hamoodyjamal

Infrared Activated Switch

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Hi all,

I’m in need of desperate help. I’ve searched ages for a simple circuit but failed to get one. What I have in mind is this. 

An Infrared transmitter will emit a signal which will be picked up by a receiver and when the path of the infrared beam is broken, the receiver will trigger a relay. The relay will be connected to an external circuit (i.e. lights, alarm etc...).

For 5+ weeks, I haven’t succeeded.

Can you please tell me where I can find a circuit of this type?

A single channel remote control will also do the job.

I don’t know if this helps, but these are some components I have (or that I can get):

- NPN photo-transistor,
- 56 KHz Infrared receiver module (Part number TSOP1756)
- 555 Timer
- LM308N OP-Amp IC
- NE567N Tone decoder
- Any resistor, capacitor, transistor (of course)
- Infrared LED's
- etc...

I of course can also get other components.

One more thing,

I just thought of an idea. If I use a 555 timer to oscillate an Infrared LED at 56 KHz, can I use the infrared receiver module (TSOP1756) to KEEP a relay switched on when the beam hits the receiver?

I thank you all very much for your help (that’s if I get any, hehe ;D).

Later!



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Hi, hamoodyjamal,


I think you are looking for a IR Beam Break Detector or a IR Barrier, try one of these links and then tell me if I’m right:

http://www.electronic-circuits-diagrams.com/alarmsimages/alarmsckt19.shtml

http://www.maplin.co.uk/Module.aspx?ModuleNo=27513&1&source=14&doy=search

http://www.hobbytron.com/product536.html

http://www.elexp.com/kit_k120.htm

http://rpelectronics.com/Default.asp?Main=/English/OnlineCat.asp?Menu=/English/Content/Categories/CatM_95.asp%26Detail=/English/Content/Items/B216.asp


;D

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Hi,

Thank you sooo much.

I prefer building the circuit my self. So, the first link was the best. If you know any more similar links to the first one, it would be greeeeeat if you could share it.

Again, thank you soo much.

Bye! :)

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Dear hamoodyjamal

The easiest way and chipest way for what you want to do is Using IC PT2262 as transmitter(Encoder) and PT2272 as receiver(Decoder).
The PT2262 creat a special 11bit Pulse dedicated On how the Input pins are connected to GND or VCC. U can send the Pulse with a infrared  module. IF PT2272 gives the correct Pulse it enables one of It outputs otherwise, disable the Output pin. These ICs are designed for these purposes. There are many similar ICs call Encoder/Decoder. They are even multichannels and you can enable 2 or 4 relays. the Schematic is in the DATASHEET. Try them.


HTH - Shahriar

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Hi,

Thanks Shahriar, but the problem is, I can’t find these IC's. I even looked in Maplin and some other shops but no luck.

As you may have read, I have an LM567 Tone Decoder. I’m not sure if this will work, but would it be possible to use an NE555 timer to oscillate i.e. 10KHz and then use an LM567 (with some resistors and capacitors to set the frequency, I think this is how it works) to activate a relay when it receives only 10KHz?

I’m just assuming how the LM567 works. Am I right? The 555 timer works using just 2 timing resistors and a timing capacitor, so I presume the 567 decoder would work similarly using resistors and a capacitor to set it to receive a certain frequency.

Thanks.  ;D

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Dear hamoodyjamal

It is Possible to Use LM567 and 555 together and it will work. I attached the schematic you need. (See Page 5)
But I beleive using Encoder and Decoder ICs is better. It is posible that You could't Find PT2262 in your area but I am sure there is At leats one of These ICs in your area. Ask a professional seller for such an Encoder/Decoder ICs and tell him what they are and what you are looking for. maybe he could help you but If You couldn't find any IC, then Use LM567 and 555.

Some of these Encoder/Decoder ICs are:

HT12E / HT12D
SC5262

You can find more by a search in      http://www.datasheetarchive.com
HTH - Shahriar

circuit17.pdf

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Dear Shahriar,

I took a look at the circuit you pointed me to, but that’s not what I'm looking for. The circuit has no optical input (i.e. phototransistor), and has a reset switch that I don’t know why it needs it.

I'll simplify things and ask a simpler question.

How do you use the LM567 IC to receive a certain frequency via a phototransistor to operate an LED, for instance?

Also, this is a side question. Would it work if you use a 555 timer to oscillate 50Hz (same frequency as the mains) then use an amplifier (with the help of a transformer) to operate low wattage 220v appliances? And would you need a centre-tap transformer?

Thanks ;D

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Hi,
You have a very good IR receiver that should be used with a 555 transmitter. If you use only 50Hz for the modulating frequency then a receiver made with an LM567 would pick-up mains hum.
Our IR Remote Control project has a CD4013 flip-flop used as a latch that maybe you could use: http://www.electronics-lab.com/projects/models/009/index.html

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Also, this is a side question. Would it work if you use a 555 timer to oscillate 50Hz (same frequency as the mains) then use an amplifier (with the help of a transformer) to operate low wattage 220v appliances? And would you need a centre-tap transformer?

Sorry, I missed this part.
The circuit for making mains AC power from a battery is called an inverter. An ordinary audio amp isn't used because it operates linear, and therefore would get very hot since the current into the step-up transformer is very high. Most inverter circuits have a square-wave output which is fine for most appliances. Since the circuit is switching the battery power on and off into the step-up transformer, the output transistors don't get too hot.
The circuit uses a center-tapped transformer to make the push-pull output transistors circuit simple.
We have a 500W inverter project: http://www.electronics-lab.com/projects/power/033/index.html

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Dear hamoodyjamal

I didn't say that this schematic is exactly what You are looking for, I sent this schematic which is designed for a RF Application but the Amplifier and LM567 section is what You are looking for, Just Connect the input to Your IR Receiver and when the expected frequency Appeared at the input the LED turns ON.
I do not Know what that reset button does, But I don't think it is very important.
I attached the LM567 Datasheet, You can find a very nice App in Page 5. Also See that AC test circuit on page 6.

HTH - Shahriar

LM567.pdf

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Hi guys,

audioguru, I’m afraid the circuit you pointed me to is somewhat complicated and I don’t need 500W. Let me rephrase my question neglecting heating and power needed. If I were to oscillate 50 Hz using a 555 timer, then connect it the BE of a high power transistor to the output of the 555 timer, and the transistor's CE would be connected in series with a battery and a step up transformer (voltage of battery and output of transformer will be the same). Would I be able to power i.e. a 220v 5 watt light? I just want to know if the idea will work.

Secondly, I managed to solve my problem. Weird no one though of this. I just got a 56 KHz Ir receiver module, and connected it correctly, to minimal components, (just a battery and a light) and when I switched on the oscillator and pointed the IR LED at the receiver, the light on the receiver lighted up. Wicked. However, can you please take a look at a block diagram I drew? Info is on the picture.

I want to add something; the beam will be across the door, so when someone passes by...you'll understand when you see the picture.

Thanks.

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Hi,
Why not just use a transistor as an inverter to drive the relay?

Why not use only a transistor to replace the relay?

You can capacitor-couple the signal to the monostable so it times-out if the beam remains blocked.

A single power transistor can be fed from a 555 through a current-limiting resistor, and used to drive a transformer to provide a square-wave at 220V/50Hz/5W. A larger than calculated transformer might be necessary because its core might saturate from the DC in its primary winding. The transistor will need a protection diode wired in reverse across the transformer's primary to arrest inductive flyback voltage spikes when the transistor turns-off.

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WOHO, hold up genius. I found a solution for my problem and I’m building it. It’s much simpler. Take a look.

Explanation.

The IR LED will be positioned across the door along with the IR Module on the same axis. The output of the receiver will always be high because it is receiving IR light at 56 KHz; this is why I added a transistor as an inverter to operate the relay. Thanks audioguru for the tip. I think I will also substitute the relay with a transistor. When the beam is broken, i.e. someone goes through the door, the receiver will output low, and the relay will be triggered and will trigger the monostable circuit which in turn will sound the alarm. I will actually add a relay instead of the alarm to switch on some lights. I just used the alarm to simplify explanation.

Weird, I couldn’t find such a circuit on the web. I might add this to some electronics site. Wicked.

What do you guys think?  ;D

Regarding the DC/AC inverter circuit, I think it should work properly. However, it was quite hard to set the 555 timer to 50Hz; it was not very stable and kept on increasing or decreasing by 1Hz every now and then. I don’t think this will be a problem for appliances that use rectifiers (i.e. Chargers). What about ones that don’t use rectifiers and work fully on AC current?

PS: audioguru, can you please explain "You can capacitor-couple the signal to the monostable so it times-out if the beam remains blocked."

Bye!

post-10092-14279142298025_thumb.gif

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Hi Hamoodyjamal Genius! ;D
Don't use a -12V supply with the IR receiver, it will blow up! :o
Your circuit will work fine without the transistor, relay and -12V supply:
1) Use a well-filtered +12V supply for the 555 because it causes a huge current spike in the supply when its output switches high and low.
2) Use a 78L05 regulator to power the IR receiver and isolate it from the current spike from the 555. Connect a 47uF capacitor on its +5V output.
3) Connect a 10k resistor to the trigger pin 2 of the 555 with its other end at +5V.
4) Capacitor-couple the low-going "IR beam is blocked" signal from the IR receiver with a 0.1uF capacitor to the trigger pin 2 of the 555.
5) Connect all the grounds together.
The capacitor-coupling allows the 555 to time-out when the IR beam is continuously blocked. ;D

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Hey audioguru,

Thanks a lot for the help.

Sadly, I didn't understand all what you said. Sounds too complicated.

Regarding the -12, I meant the negative side of the +12, you can call it ground, or 0.

Also, I have the power supply figured out for each circuit. That’s not a problem. I will be using the 78L05 regulator for the IR module, and 555 timers.

Can you please explain in a more understandable way and a reason for each comment? Sorry  :-[  for some reason I'm having trouble understanding you. Again, sorry.

Also, I still don’t understand the capacitor-coupling regarding the IR beam continuously blocked. What is meant by "time-out?"

Bye!  ;D

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Hi Hamoodyjamal,
Now your circuit certainly doesn't have a -12V supply. It has +12V and ground, or 0V.
I am sorry you don't understand, I think explained my comments simply. What don't you understand?

The end of the 10 seconds time period from the 555 is its "time-out". The datasheet for the 555 explains that it won't time-out if its trigger pin is still low just before and during its scheduled time-out. So if your IR beam is blocked for more than 10 seconds then the alarm won't shut off until the IR receiver is illuminated again by the IR.
Capacitor-coupling the low output from the IR receiver provides a brief low-going pulse to trigger the 555, then the coupling capacitor quickly charges to +5V by the 10k resistor so that the 555's trigger pin is no longer low and can time-out on schedule even if the IR beam is still blocked. ;D 

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Hi audioguru,

The time-out thing is no problem. I want the alarm to sound for 10s + the time the beam is blocked. So that’s ok.

What are current-spikes that are caused by the 555 timer? And how are they dangerous to the other components?

And what do you mean by "well-filtered", do I need to add some extra components?

BTW, do you know a code for a General Purpose transistor that can pass 1A through CE? I already have some in mind (2N2222A, TIP31); I just want a second opinion.

Thanks. ;D

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Hi Hamoodyjamal,
Since you don't care if the 555 doesn't time-out on schedule when the IR beam remains blocked, just connect the output of the IR receiver directly to the trigger pin 2 of the 555. The pull-up resistor in the output of the IR receiver will set pin 2 to +5V when it sees the beam. So you don't need a coupling capacitor nor an extra resistor.

The 555 has high-power output transistors. One transistor pulls the output high and the other pulls the output low. Because they are high-power devices, when the output switches state they both conduct about 400mA from the supply. The manufacturer recommends a 0.1uF ceramic disc plus at least 1uF on its supply to provide small filtering of the current pulse. I use a 0.1uF ceramic disc and a 100uF capacitors. Without the capacitors the supply voltage might collapse for a moment, upsetting anything on the supply.

With a 0.1uF ceramic disc and a 100uF capacitors across the supply, it is well filtered.

A 2N2222A transistor can't conduct 1A safely. Its absolute max rating is 800mA, and its min current gain of 40 is rated at 500mA.
A TIP31 has an absolute max current rating of 3A, and its min current gain of only 25 is rated at 1A. ;D   

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With a 0.1uF ceramic disc and a 100uF capacitors across the supply, it is well filtered.


Question: why dont i just use one capacitor i.e. 220uF? Also, since I will be using two 555 timers, do i need to double the values?

Regarding the transistors, i understand the TIP31 is the better choice. But if i cant find it, are there any equivilents?

;D

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An electrolytic capacitor provides poor filtering at the high frequency of the switching edge of the supply current spike caused by a 555. The 0.1uF ceramic disc capacitor is an excellent filter for medium-high frequencies due to its low inductance. At radio frequencies much smaller-values of ceramic disc capacitors are used as filters.

Each 555 needs a 0.1uF ceramic disc capacitor mounted as close as possible to its supply and ground pins. If they are close together then a single 220uF capacitor will be fine.

There are many power transistors like the TIP31 that can conduct 1A. Their availability depends on where in the world you are. ;D

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Hi audioguru,

I'll add those capacitors you told me about.

BTW, I was reading about the 555 timer set as a monostable circuit and I came across this line

"For a simple 555 monostable, the trigger pulse must be shorter than the output pulse" found at http://www.doctronics.co.uk/555.htm#triggering

Can you please explain this to me? And what are the affects if the beam is blocked for more than 10s?

Also, I live in the United Arab Emirates. There are Maplin and radioshack stores near where i live. So which transistors do you recommend i use for conducting 1A?

I dont know if this helps, but the alarm circuit draws arround 850mA which is quite close to the limits of a 1A transistor? any tips on how to avoid damage to anything?

Thanks  ;D

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