Infrared Remote Control - corrections?

Menticol

Active Member

• May 27, 2008

• #1

Hello!

I've found this simple circuit on the net, It's an single channel IR remote control. I hope somebody could find it useful.

The only problem is, I got it from a site with bad reputation of non working schematics - It's pablin.com.ar, to avoid copyright issues.

Should I correct something, before starting etching?

Emmiter
**broken link removed**

Receiver
**broken link removed**

(Receiver needs +9v -9v to work)

Thank you in advance

 

audioguru

Well-Known Member

Most Helpful Member

• May 27, 2008

• #2

It is the same defective very old circuit at Aaron's Homepage .
The LM308 opamp has not been made for about 13 years.
It is missing a 100k to 1M resistor from its pin 3 to 0V for its 0V reference voltage.
The author didn't know that the -9V battery can be replaced by a couple of resistors.

 

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Menticol

Active Member

• May 27, 2008

• #3

Damn! I just got the Lm308 today, 13 years old? Now I know why I had to pay a lot for it!!!

Please Audioguru, is the 100 ohm resistor (I have chosen it randomly between 100K and 1M) between pin 3 and GND, enough to avoid the using of -9V on pin 4? or where should the pin 4 be connected?

The datasheet doesn't give me any help.

Thank you in advance, and sorry by the nuisance

 

Last edited: May 27, 2008

audioguru

Well-Known Member

Most Helpful Member

• May 27, 2008

• #4

The added 100k to 1M resistor (not 100 ohms) makes pin 3 input of the opamp at 0VDC when the opamp has a positive and negative supply. If the opamp has only a single positive supply then pin 3 must be biased at half the supply voltage with two resistors.

 

Menticol

Active Member

• May 27, 2008

• #5

Thank you so much Audioguru, you saved my day again!

Is this the correct way to biasing pin 3?


**broken link removed**

I made the calculation as follows

Power consumption of the circuit: 300 mA
Supply voltage: 9V
R = 4,5 / 0,300 = 15 ohm

One last question: If my procedure is correct, can I feed the circuit with only 5V? My project will run with 12V, the LM308 can handle up to 18, but LM567 just can handle 9... and I have a 7805 at hand

Recalculating R1 again offcourse

 

Last edited: May 27, 2008

audioguru

Well-Known Member

Most Helpful Member

• May 27, 2008

• #6

No.
Pin 3 is the input of the LM308. Its current is almost nothing, certainly not 300mA. The entire circuit draws about 10mA plus the current for the relay. The pin 3 input current of the opamp is only 0.0000000015A (1.5nA).

Your 15 ohm resistor is shorting the output signal from the photo-transistor and is shorting the input of the opamp to the positive supply where it does not work.

Pin 4 must be connected to 0V then pin 3 has a 1M (one million ohms) to ground and another 1M to the positive supply. Then pin 3 will be at half the supply voltage.

 

Menticol

Active Member

• May 27, 2008

• #7

Hahaha I was proclaiming victory too soon. i'm correcting it right now.

Thank you again by your time!!

 

Menticol

Active Member

• May 27, 2008

• #8

It doesn't work. When I adjust the Potenciometer, the relay activates only when I reach the end of it, and ignores the emmiter. At some point of the potenciometer scale one of the IC's starts making a high frecuency noise

tested with 2 pin and 3 pin IR receiver

Don't know what to do...

 

Last edited: May 27, 2008

audioguru

Well-Known Member

Most Helpful Member

• May 28, 2008

• #9

The circuit is supposed to use a photo-transistor. It will not work with a photo-diode and it won't work with an IR receiver.
If the pins on the photo-transistor are backwards then the circuit will not work.
If the photo-transistor is in light then it probably will not work.

 

Last edited: May 28, 2008