Need help>> as soon as possible! - Page 4 - Electronic Circuits Projects Diagrams Free

Abeer_engjbr · 16th February 2008, 02:02 PM

Hi Kmoffet,

I want to know what is the purpose of 555 timer in the ir repeater circuit, how exactly does it work, I've tried to read the link that bluelectronic wrote but am so confussed, especially when i read the Datasheet.
Thank you.

blueroomelectronics · 16th February 2008, 04:23 PM

The TSOP1738 strips away the 38kHz carrier so the signal is simply data, the 555 freeruns at 38khz to remodulate the data back to 38kHz. Not sure if this link will help but it's worth a look.
http://www.sixca.com/eng/articles/remote/index.html

Abeer_engjbr · 17th February 2008, 08:57 PM

I understood the purpose of TSOP1738, and why we use the 555 timer, but, on the other hand i still can't get what equations i must use in order to get specific frequancy ( 38 kHz for instant).
I've read the datasheet of LM555, and there is many functions for it, I can't figure out what is the name of it in the ir repeater circuit in order to know what equations i must use to determine C and R values to get a certain frequancy , how 555 is reset by the collecter of the junction (in the circuit) , and why 5 volt or 12.
When i asked some engineers about 555 they said that it is a modulation timer, can i build a repeater circuit without it?
Thank you.

blueroomelectronics · 17th February 2008, 10:25 PM

http://www.csgnetwork.com/ne555timer2calc.html
Has a 555 timer calculator. Just plug in the numbers till you get 38,000 Hz.
Use the reset pin to modulate the pulse.

Abeer_engjbr · 18th February 2008, 07:38 AM

Hey
Does that mean that the 555 function or name in the ir repeater circuit is ( Astable 555 square wave ). But realy if that so , I've noticed that it doesn't have the same connections in the circuit as Astable connections ( for examlpe pin 7 in the repeater circuit is not connected between R1 and R2 aas it does in the Astable circuit you show me ( and i saw on the datasheet ).

Please help me get a clearer idea , I'm so confused right now!!!

Abeer_engjbr · 3rd March 2008, 04:47 PM

Hi Everyone,
Miss me? I don't think so! Any way if you don't remember as I'am sure of, I asked about the IR REPEATER circuit, I constructed it and there was a problem, IT DID NOT WORK! any way i still have plenty of time to try make it work but here's what i did:
1) You have advised me to use 9 Volt instead of the voltage regulator in the output part, and that's what I did. But realy i think it's more conveniant to put a regulator.(I'll try it tomorrow) .

2) In the LM555 connection, it is obviously connected as Astable circuit, but what must I put in the DIS pin, as it is not connected to anything, and as far as I know I connect it to a capacitor (1 n) with the grounded .(is it right?).

3) What is the function of the capacitor that is connected before the Voltage Regulator, and the capacitor between Vcc and GRD in 555 IC?

4) I've placed an oscliscope on the 2 K

hm: that is connected to the OUT of 555, and nothing happened on the screen after I pointed the IR signal to the input Photodiode, and the Led did not flash.( for these resones I asumed that it did not work! is that so?)

Thank you all, I Hope To Hear From You Soon.
The Link You Gave Me Is:http://english.cxem.net/infrared/ir7.php:)

Abeer_engjbr · 3rd March 2008, 04:55 PM

KMoffett · 3rd March 2008, 06:01 PM

Quote:

Originally Posted by Abeer_engjbr

Hi Everyone,
Miss me? I don't think so! Any way if you don't remember as I'm sure of, I asked about the IR REPEATER circuit, I constructed it and there was a problem, IT DID NOT WORK! any way i still have plenty of time to try make it work but here's what i did:
1) You have advised me to use 9 Volt instead of the voltage regulator in the output part, and that's what I did. But realy i think it's more convenient to put a regulator.(I'll try it tomorrow) .

Either way, but the 12v will provide a slightly higher output on the LEDs.

Quote:

2) In the LM555 connection, it is obviously connected as Astable circuit, but what must I put in the DIS pin, as it is not connected to anything, and as far as I know I connect it to a capacitor (1 n) with the grounded .(is it right?).

DIS should be connected to the junction of R4 and PR1. Won't work otherwise.

Quote:

3) What is the function of the capacitor that is connected before the Voltage Regulator, and the capacitor between Vcc and GRD in 555 IC?

These are to filter out possible noise on the +12v ...but...if you are going to use the regulator change C4 to 0.1UF and add another 0.1uF capacitor on the 15v side of the regulator, between the IN and COM terminals. Both of these caps should be as close as physically possible to the regulator pins.

Quote:

4) I've placed an oscliscope on the 2 K

hm: that is connected to the OUT of 555, and nothing happened on the screen after I pointed the IR signal to the input Photodiode, and the Led did not flash.( for these resones I asumed that it did not work! is that so?)

Because the 555 was not working. I also notice is the second schematic the 555 circuit id different, and didn't see an explanation.

Ken

Quote:

Thank you all, I Hope To Hear From You Soon.
The Link You Gave Me Is:http://english.cxem.net/infrared/ir7.php:)

And your smiley face got in you URL link.

Abeer_engjbr · 3rd March 2008, 07:49 PM

Sorry, The URL link is:
http://english.cxem.net/infrared/ir7.php
Is your explanation about circuit 1?

Abeer_engjbr · 3rd March 2008, 07:50 PM

or must I be

audioguru · 3rd March 2008, 08:39 PM

DO NOT connect the DIS pin of the 555 to anything. The OUT pin is part of the oscillator in this circuit instead of the DIS pin.

Abeer_engjbr · 3rd March 2008, 08:45 PM

Realy? But is the first circuit correct or the second ( must i use 2 resistors to the 555 as the first circuit (R4 and PRE1), or just 15 as the second circuit?)

Abeer_engjbr · 3rd March 2008, 08:47 PM

What do you mean by (It's part of the oscillator)?

audioguru · 3rd March 2008, 09:00 PM

Other 555 oscillators have the DIS pin operating the oscillator.
This oscillator is different.
The resistor R4 from the OUT pin charges and discharges the C2 timing capacitor that is connected to the TRG and THR pins.
The DIS pin in this oscillator is not connected to anything.

Abeer_engjbr · 3rd March 2008, 09:06 PM

Thank You!
I'll connect again it tomorrow and see the results.
If you read what in the reply before you, is the rest true?

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

16th February 2008, 02:02 PM	(permalink)
Abeer_engjbr	Hi Kmoffet, I want to know what is the purpose of 555 timer in the ir repeater circuit, how exactly does it work, I've tried to read the link that bluelectronic wrote but am so confussed, especially when i read the Datasheet. Thank you.

16th February 2008, 04:23 PM	(permalink)
blueroomelectronics	The TSOP1738 strips away the 38kHz carrier so the signal is simply data, the 555 freeruns at 38khz to remodulate the data back to 38kHz. Not sure if this link will help but it's worth a look. http://www.sixca.com/eng/articles/remote/index.html __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com

17th February 2008, 08:57 PM	(permalink)
Abeer_engjbr	I understood the purpose of TSOP1738, and why we use the 555 timer, but, on the other hand i still can't get what equations i must use in order to get specific frequancy ( 38 kHz for instant). I've read the datasheet of LM555, and there is many functions for it, I can't figure out what is the name of it in the ir repeater circuit in order to know what equations i must use to determine C and R values to get a certain frequancy , how 555 is reset by the collecter of the junction (in the circuit) , and why 5 volt or 12. When i asked some engineers about 555 they said that it is a modulation timer, can i build a repeater circuit without it? Thank you.

17th February 2008, 10:25 PM	(permalink)
blueroomelectronics	http://www.csgnetwork.com/ne555timer2calc.html Has a 555 timer calculator. Just plug in the numbers till you get 38,000 Hz. Use the reset pin to modulate the pulse. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com

18th February 2008, 07:38 AM	(permalink)
Abeer_engjbr	Hey Does that mean that the 555 function or name in the ir repeater circuit is ( Astable 555 square wave ). But realy if that so , I've noticed that it doesn't have the same connections in the circuit as Astable connections ( for examlpe pin 7 in the repeater circuit is not connected between R1 and R2 aas it does in the Astable circuit you show me ( and i saw on the datasheet ). Please help me get a clearer idea , I'm so confused right now!!!

3rd March 2008, 04:47 PM	(permalink)
Abeer_engjbr	Hi Everyone, Miss me? I don't think so! Any way if you don't remember as I'am sure of, I asked about the IR REPEATER circuit, I constructed it and there was a problem, IT DID NOT WORK! any way i still have plenty of time to try make it work but here's what i did: 1) You have advised me to use 9 Volt instead of the voltage regulator in the output part, and that's what I did. But realy i think it's more conveniant to put a regulator.(I'll try it tomorrow) . 2) In the LM555 connection, it is obviously connected as Astable circuit, but what must I put in the DIS pin, as it is not connected to anything, and as far as I know I connect it to a capacitor (1 n) with the grounded .(is it right?). 3) What is the function of the capacitor that is connected before the Voltage Regulator, and the capacitor between Vcc and GRD in 555 IC? 4) I've placed an oscliscope on the 2 Khm: that is connected to the OUT of 555, and nothing happened on the screen after I pointed the IR signal to the input Photodiode, and the Led did not flash.( for these resones I asumed that it did not work! is that so?) Thank you all, I Hope To Hear From You Soon. The Link You Gave Me Is:http://english.cxem.net/infrared/ir7.php:)

3rd March 2008, 07:49 PM	(permalink)
Abeer_engjbr	Sorry, The URL link is: http://english.cxem.net/infrared/ir7.php Is your explanation about circuit 1?

3rd March 2008, 07:50 PM	(permalink)
Abeer_engjbr	or must I be

3rd March 2008, 08:39 PM	(permalink)
audioguru	DO NOT connect the DIS pin of the 555 to anything. The OUT pin is part of the oscillator in this circuit instead of the DIS pin. __________________ Uncle $crooge

3rd March 2008, 08:45 PM	(permalink)
Abeer_engjbr	Realy? But is the first circuit correct or the second ( must i use 2 resistors to the 555 as the first circuit (R4 and PRE1), or just 15 as the second circuit?)

3rd March 2008, 08:47 PM	(permalink)
Abeer_engjbr	What do you mean by (It's part of the oscillator)?

3rd March 2008, 09:00 PM	(permalink)
audioguru	Other 555 oscillators have the DIS pin operating the oscillator. This oscillator is different. The resistor R4 from the OUT pin charges and discharges the C2 timing capacitor that is connected to the TRG and THR pins. The DIS pin in this oscillator is not connected to anything. __________________ Uncle $crooge

3rd March 2008, 09:06 PM	(permalink)
Abeer_engjbr	Thank You! I'll connect again it tomorrow and see the results. If you read what in the reply before you, is the rest true?