Infrared Activated Switch

[audioguru2]

Hi Hamoodyjamal,
It's too bad you blew-up your IR receiver. The TSOP1756 and TSOP1156 are almost the same, the TSOP1156 has a slightly quicker data rate.

I noticed that they reduce their sensitivity during continuous IR at 56kHz, since their max number of 56kHz cycles is 70. Your system will have better range if you transmit IR modulated with bursts of no more than 70 cycles (with a gap of at least 10 cycles) of 56Khz IR. Then the output of the receiver will be low during each burst, then high for each gap. You could use a peak detector circuit to blend the bursts together, and its output will be continuously low when your modulated IR beam is shining on the receiver, and high when the beam is blocked. ;D

View attachment 37285

View attachment 37286

 

[hamoodyjamal]

Hi audioguru,

That picture you attached which shows the effects for DATA. Im just sending plain IR light at 56KHz.

See image attached.

BTW, range isn't that important. Probably 1-4 meters is what i'll need. What you say?

;D

View attachment 37287

 

[audioguru2]

Hi audioguru,

That picture you attached which shows the effects for DATA. Im just sending plain IR light at 56KHz.

See image attached.

BTW, range isn't that important. Probably 1-4 meters is what i'll need. What you say?

;D

Then for your continuous modulation, the receiver's gain is reduced by its AGC. They don't say how much the gain is reduced so you will have to try it to see. ;D

 

[hamoodyjamal]

Hi audiofuru,

AGC?  ???

;D

 

[audioguru2]

AGC is Automatic Gain Control.

 

[hamoodyjamal]

Hi audioguru,

Problems after Problems!!!! Grrrrrrrrrrrrrrrrrrrrrrrrrrrrrr.

During the testing procedures, I used a 9v battery to power the 555 timers. Everything was OK. Now, I used a 220V-12V transformer to power the 555 timers. Problem. The IC quickly overheats. I checked for wiring errors but all was fine. So I measured the current and it read 220mA which is darn a lot. I went back to using the 9v battery and everything was OK. Current with the 9v is around 35mA. I’m stuck on why the IC overheats when using the transformer (BTW, the transformer output is rectified and decoupled with an electrolytic capacitor of values 16v 1000uF). I asked my dad (who’s an electrical engineer) and said that the battery has internal resistance. I don’t know what he meant by that. What you say?

Also, the TSOP1756 IR receiver turns out to actually be working. I thought it was busted, but it wasn't. I used it for testing, but now I really burnt it. Ahhhhhhhhhhhhhh. A problem with the TSOP1156 is that the output goes low for a split second when there is IR light. Where as the previous one (TSOP1756) kept low when there was IR light. How can I fix this dilemma?

Thanks!  ;D

 

[audioguru2]

Now, I used a 220V-12V transformer to power the 555 timers. Problem. The IC quickly overheats. So I measured the current and it read 220mA which is darn a lot.(BTW, the transformer output is rectified and decoupled with an electrolytic capacitor of values 16v 1000uF).

Did you measure the supply voltage? A 12VAC transformer's output might be 16V when it is not fully loaded, and rectifying and filtering it could result in 21.2V. The absolute max for an ordinary 555 is 18V and only 15V for the Cmos version. What is its load? What is regulating the 5V for the IR receiver?

A problem with the TSOP1156 is that the output goes low for a split second when there is IR light.

The IR receivers are designed to receive data, not continuous nor continuously modulated IR. They have an automatic-gain-contol system to reduce their gain if continuous IR (interference) is received. It probably takes a split second for the AGC to reduce the receiver's gain. The manufacturer doesn't say how much the gain is reduced by the interfering IR, so each one is probably a little different.

Like I said before, modulate the IR in bursts of 56kHz which would keep the AGC at full gain. Then add a peak detector to its output to blend the bursts together into a steady output. Here is an IR receiver kit that does that:  View attachment 37289

 

[hamoodyjamal]

Hi audioguru,

How can rectifying and filtering a transformer’s o/p increase its voltage? I don’t find it logical.

By the way, I have a NE567 Tone-Decoder IC and am wondering on how to use it to replace those IR receivers that gave me such a headache.

Can I use it to receive IR light, using a phototransistor as the input, oscillated at 56 KHz to drive a relay? Or just give a HIGH or LOW signal?

I took a look at the datasheet and it showed me how to calculate the center frequency. That was Ok. But then I came across how to calculate the detection bandwidth and I was stuck on what it is? I thought it could be something similar to tolerance of the frequency? Am I right?

Thanks! ;D

 

[audioguru2]

How can rectifying and filtering a transformer’s o/p increase its voltage? I don’t find it logical.

Hi Hamoodyjamal,
The 12VAC output of a fully loaded 12V transformer has the same heating power as 12VDC. Since the AC voltage changes polarity, it frequently passes through zero volts when it provides no power. In order for the average power to be the same as with 12VDC, the AC peak voltage is 1.414 times (the root of 2) its 12V RMS value. A rectifier and filter cap charges the cap to the peak voltage, minus a diode drop or two.

By the way, I have a NE567 Tone-Decoder IC and am wondering on how to use it to replace those IR receivers that gave me such a headache.

Can I use it to receive IR light, using a phototransistor as the input, oscillated at 56 KHz to drive a relay? Or just give a HIGH or LOW signal?

The project in our Projects Section http://www.electronics-lab.com/projects/motor_light/030/index.html uses a phototransistor, opamp and LM567 driving a relay. I don't know what frequency or bandwidth it has, and its opamp is obsolete and is incorrectly biased.

I took a look at the datasheet and it showed me how to calculate the center frequency. That was Ok. But then I came across how to calculate the detection bandwidth and I was stuck on what it is? I thought it could be something similar to tolerance of the frequency? Am I right?

Detection bandwidth is how far the incoming frequency is away from the tuning frequency of the LM567, but the LM567 can still lock-on to it. If the bandwidth is too wide, it might lock-on to interference at a different frequency than your 555. If it is too narrow, it might not lock-on to the 555 who's frequency isn't very stable. ;D

 

[steven2]

if your looking for an infrared activated switch youll find a really simple one in the topic fairchild photo transistor data and if you want to see how simple it looks look at topic keychain laser power supply as the infrared  switch or light activated realy circuit that uses the fair child photo transistor allso detects laser at a large distance away

 

[hamoodyjamal]

Hi audioguru,

I found out the problem for the 555 timer overheating. I was looking at the datasheet (of the 555) and it said R1 and R2 should be between 1K and 1M. Before i was using, R1 and R2 which added up to 147 Ohm which is way too small. So i changed the components to still give 56KHz and the 555 timer stopped over heating. Great.

BTW, i want to use an LM307 IC to power a Relay (instead of a transistor becasue a transistor is a SEMIconductor which will always trigger the 555 monostable since its very sensative to triggering) from the output of the receiver. I found a circuit on how to set it up. At first it worked. But then after re-setting it up (dont bother to ask why), it didn't work. I double checked for connection errors but everything is fine. Yet, it just doesn't want to work. I drew a picture of the schematic that i set up. Can you spot a problem?

This may help you, im using the same supply to power both the LM307 and the IR receiver, while using a 12v and a 5v regulator for the LM307 and the IR recevier respectavly. Could there be conflict issues?

Thanks! ;D

View attachment 37338

 

[audioguru2]

Hi Hamoodyjamal,
You need a transistor to drive the low resistance relay because the obsolete LM307 can't supply enough current to drive it.
Most opamps have a minimum load spec of 2k. Your relay is only 245 ohms! The LM307 current-limits its output current at 25mA. 25mA through 245 ohms is only 6.13V. A 12V relay won't work with only 6V. The opamp can easily drive the base of a transistor through a couple of resistors as a voltage divider. The voltage divider is necessary because the output voltage of the opamp doesn't go low enough to turn off the transistor.

Also, the relay's coil is an inductance. When current is turned off to an inductance it produces a very high voltage across the coil as the magnetic field collapses. A diode is required to be connected across the relay coil in reverse, to arrest the high voltage and protect the relay driver from being fried. ;D 

 

[hamoodyjamal]

Hi audioguru,

Im having alot of trouble from the IR receiver module. Dont bother to ask why. After my first one got fried (which was perfect), ive been having alot of trouble. I couldnt get the exact same one and thus am having trouble with the new ones (As i mentioned before). So what i have in mind is using a Tone Decoder (Such as the obselete Philips NE567) to decode a 40KHz freqency using a phototransistor.

When it comes to the circuitry, i looked at the datasheet of the NE567 but read some things such as the bandwidth that i have no knowledge about ???(I deducted it could be like tolerance). I think what im looking for is a circuit like the one in arroncake's page. IR remote (http://www.aaroncake.net/circuits/irremote.htm) but many have complained that it didnt work. Can you shed some light on this subject : how to build a tone decoder. It may need an op-amp to amplify the phototransistor signal.

Thanks ;D

 

[audioguru2]

Hi Hamoodyjamal,
Aaron's IR receiver circuit is missing a very important 100k resistor from pin 3 of the opamp to ground. It doesn't have AGC so it is easily overloaded by ambient light and IR from sunshine. Its slow opamp can't function at 40kHz. 
I don't know if a phototransistor can switch fast enough to detect 40kHz, usually a much quicker photo-diode is used.

 

[hamoodyjamal]

Hi audioguru,

Say i add the 100K resistor to the op-amp, and i reduce the freqency to say 200Hz (or what ever the photo transistor can detect - SFH300), and i get a 741 op-amp, will it work then?

Regarding the AGC, i dont need that. I actually dont want it. And since ill be setting the center frequency of the tone decoder to about 200Hz, i dont think there will be any interferance from ambiant light. What you say?

I will be using the circuit found at (http://www.reconnsworld.com/schemdepot/cgi-bin/ikonboard.cgi?s=a7212d5f7c71e899286c2e9a1677dfb8;act=ST;f=11;t=1) and the IR remote control on Arron's page as a refrence. Good?

BTW, that -9v on the op-amp (ir remote control in arron's page), is it really -9v or just ground? It seems too high for an op-amp. No?

Thanks ;D

 

[hamoodyjamal]

Never mind about the detection bandwith as you already answered it before. Silly me, i forgot all about it. Thanks ;D

 

[audioguru2]

Say i add the 100K resistor to the op-amp, and i reduce the freqency to say 200Hz (or what ever the photo transistor can detect - SFH300), and i get a 741 op-amp, will it work then?

The SFH300 phototransistor is in a clear case and detects all light plus IR. A SFH300FA is in a black case which is an IR filter and doesn't respond much to visible light.
A frequency as low as 200Hz is very close to double the mains frequency produced by mains-powered electric lights and would cause severe intrerference.
An old 741 opamp is also very slow with a cutoff frequency of only about 8kHz.

I would try a black phototransistor at 10kHz or higher and use a more-modern (only 20 years old) TL071 opamp that has a 100kHz cutoff frequency. Really we should be using a black photodiode like everyone else and operate it at 40kHz.

Regarding the AGC, i dont need that. I actually dont want it. And since ill be setting the center frequency of the tone decoder to about 200Hz, i dont think there will be any interferance from ambiant light. What you say?

Besides interference from mains-powered electric lights, a phototransistor without AGC saturates easily from ambient heat and light. When it is saturated then it doesn't work anymore.

I will be using the circuit found at (http://www.reconnsworld.com/schemdepot/cgi-bin/ikonboard.cgi?s=a7212d5f7c71e899286c2e9a1677dfb8;act=ST;f=11;t=1) and the IR remote control on Arron's page as a refrence. Good?

I have never used an old NE567. Aaron doesn't spec an operating frequency for his IR transmitter.

BTW, that -9v on the op-amp (ir remote control in arron's page), is it really -9v or just ground? It seems too high for an op-amp. No?

The -9V in the receiver circuit is a second 9V battery for its negative supply. Most opamps operate with a total of 30V, with +15V and -15V. Aaron's receiver would need a couple of resistors and capacitors added to work with just one 9V battery. ;D

 

[hamoodyjamal]

Hi audioguru,

The thing is, it was somewhat difficult to get my hands on a phototransistor, yet enough, get a photodiode. But ill try.

I was looking through the datasheet of the NE567 and showed my how to calculate the center freqency. But it doesn't mention what unit to use for the Capacitor (i know its Farad, but, nF, or uF or F) because in the bandwith calculation, it tells you to use uF for the capacitor value. So, im confused here. What do you think?

BTW, i used my multimeter (set on Duty %) to check the duty cycle of my 555 timer output and gave me values between 7% - 46% , as i changed R2(4.7K POT). I think i need 50% yeah? Which might mean i need to change R1 and R2 to give 40KHz and a 50% duty cycle. Maybe this is the reason for my IR receiver not responding well. No?

Thanks.

 

[audioguru2]

Hi Hamoodyjamal,
National Semi still make an LM567. Its datasheet shows the calculation for frequency and a test circuit. Just use their test circuit with a 10k pot adjusted about halway to replace their 2.4k resistor.

I don't know if the Duty % reading of your multimeter is accurate at high frequencies. The duty-cycle of a 555 is easy to calculate because the cap charges through two resistors and discharges though one. I think the 567 works best with near 50%.

Please post the schematic of whichever IR transmitter circuit you tested recently to see its duty-cycle and IR LED current. ;D

View attachment 37375

 

[hamoodyjamal]

Hey audioguru,

I have that AC test circuit along with the equation. I actually have the same page. But the problem is that i dont know if to use uF or F for C1. C2 it tells you to use uF. This confused me if weather to use uF also for C1.

Im using a general design for the oscilator but ive drawn it anyway. When i change R2, Duty % changes. What does that tell me?

Thanks ;D

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