how to convert the signal received by Tsop1738 ir receiver to steady output?

emb · Jun 10, 2018

Hi All ,,

I want to convert the signal received by IR Receiver Tsop1738 to steady output level for example 1 if there is ir signal 0 if no Ir signal received(an object cross Ir beam).

the signal received by the receiver as the following:

>>as you see in figure above the received signal is square wave 32hz(2ms off/29ms on).
>> if there is no signal received due to object cross the ir beam the output of the tsop1738 goes high and still high while the object cross the beam.
>>I see i can do what i need using 555 timer and other ic's like 74123 but i don't want to use them
>>minimum time for crossing the beam 20ms.

>>The transmitter circuit

as you see the circuit send 38khz for 2ms and off for 29ms.

Regards

Nigel Goodwin · Jun 10, 2018

You could use another 555 timer, google for '555 missing pulse detector'.

gophert · Jun 10, 2018

Mashare said:
I see i can do what i need using 555 timer and other ic's like 74123 but i don't want to use them

Do you need a 0-5V output from the additional circuit or would a 0-3.3V output work?

emb · Jun 10, 2018

gophert said:
Do you need a 0-5V output from the additional circuit or would a 0-3.3V output work?

0-5 v

emb · Jun 10, 2018

Nigel Goodwin said:
You could use another 555 timer, google for '555 missing pulse detector'.

I don't need to use 555 timer

alec_t · Jun 10, 2018

Will this do?

Nigel Goodwin · Jun 10, 2018

Mashare said:
I don't need to use 555 timer

You don't 'need' to, but it's an effective and simple solution.

Personally I'd have used a PIC processor in the first place, greatly simplifying the project

emb · Jun 10, 2018

alec_t said:
Will this do?
View attachment 113340

I connect the output to 4518 counter..
No increment when I cross the beam

emb · Jun 10, 2018

Nigel Goodwin said:
You don't 'need' to, but it's an effective and simple solution.

Personally I'd have used a PIC processor in the first place, greatly simplifying the project

No need to MCU ..

OK..IN missing pulse circuit using 555 how I choose R,C ?

Nigel Goodwin · Jun 10, 2018

Mashare said:
No need to MCU ..

OK..IN missing pulse circuit using 555 how I choose R,C ?

Google it like I said - the operation of it is very easy to understand.

crutschow · Jun 10, 2018

Here are a couple missing pulse detector circuits as alternatives to a 555 circuit.

gophert · Jun 10, 2018

Here is 0-5V out. No 555 but a NPN and PNP to keep from inverting and avoiding a diode voltage drop at the output.

The envelope filter will react to a loss of signal in 0.5 mSec (5 time constants).

emb · Jun 10, 2018

gophert said:
Here is 0-5V out. No 555 but a NPN and PNP to keep from inverting and avoiding a diode voltage drop at the output.

The envelope filter will react to a loss of signal in 0.5 mSec (5 time constants).

View attachment 113351

I see 38khz ..
The received signal 32 Hz..94% DC
Does your circuit work if 32hz used ?

emb · Jun 10, 2018

Nigel Goodwin said:
Google it like I said - the operation of it is very easy to understand.

Thank you I got it

emb · Jun 10, 2018

crutschow said:
Here are a couple missing pulse detector circuits as alternatives to a 555 circuit.

*Can I use lm358 instead of lm393 ?
**For my received signal should I change the value of capacitors and resistors ?
***what is the purpose of c2 and D1?
****which the two circuit better using lm393 or using 4093 ?

Regards

gophert · Jun 10, 2018

Mashare said:
I see 38khz ..
The received signal 32 Hz..94% DC
Does your circuit work if 32hz used ?

Yes, works fine.

crutschow · Jun 11, 2018

Mashare said:
Can I use lm358 instead of lm393 ?

No.
The circuit requires the open-collector output of the comparator to operate properly.

Mashare said:
For my received signal should I change the value of capacitors and resistors ?

As stated in my writeup, you select the R1C1 value to be somewhat longer than the pulse period.

Mashare said:
what is the purpose of c2 and D1?

C2 is to differentiate the pulse edge, giving a short pulse trigger the circuit, and also block the DC bias from the input.
D1 clamps the differentiated pulse from going significantly below ground.

Mashare said:
which the two circuit better using lm393 or using 4093 ?

The LM393 circuit's trigger levels, determined by resistors, are more accurate than the 4093's. which depend upon the internal hysteresis value of the 4093 Schmitt trigger input.
But either circuit should be more than adequate to do the job.

emb · Jun 11, 2018

gophert said:
Yes, works fine.

I test the your circuit the output if the object cross the ir signal high and if there is no object cross the ir signal the output square wave with short off time ^^

emb · Jun 11, 2018

crutschow said:
No.
The circuit requires the open-collector output of the comparator to operate properly.
As stated in my writeup, you select the R1C1 value to be somewhat longer than the pulse period.
C2 is to differentiate the pulse edge, giving a short pulse trigger the circuit, and also block the DC bias from the input.
D1 clamps the differentiated pulse from going significantly below ground.
The LM393 circuit's trigger levels, determined by resistors, are more accurate than the 4093's. which depend upon the internal hysteresis value of the 4093 Schmitt trigger input.
But either circuit should be more than adequate to do the job.

Thank you

The received signal period about 31 ms .
Is this mean Any object cross the ir signal in time below 31ms can't detect it ?

crutschow · Jun 11, 2018

Mashare said:
The received signal period about 31 ms .
Is this mean Any object cross the ir signal in time below 31ms can't detect it ?

Not 100%.
If one pulse is interrupted, then the output will go high for one pulse.
If the object passes so fast that it doesn't block at least one pulse, then obviously it can't be detected.

A block of one pulse is shown in the simulation below for an R1C1 of 31ms.
The output goes high about 33ms after the loss of one input pulse and stays high until the next pulse is received.

how to convert the signal received by Tsop1738 ir receiver to steady output?

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