Sensers Help needed badly>>>>>>>

[bhardu]

i m working on a line follower robot.But it seems lyk the sensors are creating a lot of twist in my Brain.(They r simply not working)
i m using IR Led and a single IR detecter (the dectecter 1738,1756 i dont remember right now exactly its number)
for proper functioning i need atleast 3V output form the detecter but it shows hardly .44mV. Irrespective of the fact whether it is detecting IR light or not.

One more thing i vud like to clear that how vud i be able to get a good Voltage level difference (0V & 5V Roughly) using the IR senser & Detecter pair.
show me some way out.....thanx.

 

[MLOTZ]

hi , I've used the tsop1738 before and it worked 100% giving me 5V and was quite stable.

will it be possible to post your data I'll look at it.
martin

 

[ikalogic]

i m working on a line follower robot.But it seems lyk the sensors are creating a lot of twist in my Brain.(They r simply not working)
i m using IR Led and a single IR detecter (the dectecter 1738,1756 i dont remember right now exactly its number)
for proper functioning i need atleast 3V output form the detecter but it shows hardly .44mV. Irrespective of the fact whether it is detecting IR light or not..

are you sending Pulsed IR at 40Khz?

One more thing i vud like to clear that how vud i be able to get a good Voltage level difference (0V & 5V Roughly) using the IR senser & Detecter pair.
show me some way out.....thanx.

this is where most of time an Operational Amplifier come in handy.. search for 'op-amps as comparators', you'll find what you need

 

[bhardu]

are you sending Pulsed IR at 40Khz?

this is where most of time an Operational Amplifier come in handy.. search for 'op-amps as comparators', you'll find what you need

Yes i m using 38Khz(approx) pulsed IR.
Can i use ADC converter to convert Analog signal of 0V , 4V to convert it to Digital instead of Opamp Comparator.so that it can be directly fed to Microcontroller 8051

 

[ikalogic]

Yes i m using 38Khz(approx) pulsed IR.
Can i use ADC converter to convert Analog signal of 0V , 4V to convert it to Digital instead of Opamp Comparator.so that it can be directly fed to Microcontroller 8051

What???

the output of you'r IR receiver is allready digital, usualy they are active low, meaning they output 0V when you receive IR.. search the thread for similar issues, i remeber we were just solving a similar problem for '''Ayane'''..

why would need an ADC?

 

[audioguru]

An IR receiver IC has a very low max allowed output current. It is a max low current allowed of only 5ma for a TSOP1738 and it has a pullup resistor of 80k that supplies only 12.5uA high current at 4V.

What are you driving with it?

 

[bhardu]

What???

the output of you'r IR receiver is allready digital, usualy they are active low, meaning they output 0V when you receive IR.. search the thread for similar issues, i remeber we were just solving a similar problem for '''Ayane'''..

why would need an ADC?

the uC that i m using is 8051 it is not having inbuild ADC n i need to convert the o/p of the sensors to digital form so as to feed it to uC ....
am i going in right direction ??
Do i really need a ADC to get digital o/p which can be feed to uC /

 

[bhardu]

An IR receiver IC has a very low max allowed output current. It is a max low current allowed of only 5ma for a TSOP1738 and it has a pullup resistor of 80k that supplies only 12.5uA high current at 4V.

What are you driving with it?

first of all thnx for the reply

Basically i want to send digital I/P to uC 8051 using IR sensors...
is it possible without use of ADC


plz do reply ASAP..

 

[bhardu]

O/P from IR sensor vud b send to ADC n then the 8bit data(produced by ADC) in binary form(digital form) vud be feed to uC ...

can this logic be implemented without using comparator ?

reply ASAP

 

[bhardu]

i mean whether ADC wud be sufficient to get analog IP from sensors...or do i need to use a Comparator inbetween the IR sensor n ADC ???

i m screwed ..can nyone hhelp me

 

[ikalogic]

OMG! couldn't you write all this in one mesage?

the sensor you use is probably not a range finder, it's only a proximity sensor, so it's output is allready DIGITAL, as said before.. the output would be either approx 5v either 0V. and after reading the datasheet:
**broken link removed**
this sensor is ineed active Low, meaning it will give you 0V when it receives any ammount of 38Khz pulsed IR...

again the output IS digital, you you don't need a ADC!

in replie to your last message, well neither an ADC nor a comparator will give you analog output, because the sensor doesn't support this from the geginng..

you need to build you'r own sensor using a photodiode, phototransistor or LDR...

good luck

 

[bhardu]

slow shift in voltmeter was observed

OMG! couldn't you write all this in one mesage?

the sensor you use is probably not a range finder, it's only a proximity sensor, so it's output is allready DIGITAL, as said before.. the output would be either approx 5v either 0V. and after reading the datasheet:
**broken link removed**
this sensor is ineed active Low, meaning it will give you 0V when it receives any ammount of 38Khz pulsed IR...

again the output IS digital, you you don't need a ADC!

in replie to your last message, well neither an ADC nor a comparator will give you analog output, because the sensor doesn't support this from the geginng..

you need to build you'r own sensor using a photodiode, phototransistor or LDR...

good luck

OMG! couldn't you write all this in one mesage?

the sensor you use is probably not a range finder, it's only a proximity sensor, so it's output is allready DIGITAL, as said before.. the output would be either approx 5v either 0V. and after reading the datasheet:
**broken link removed**
this sensor is ineed active Low, meaning it will give you 0V when it receives any ammount of 38Khz pulsed IR...

again the output IS digital, you you don't need a ADC!

in replie to your last message, well neither an ADC nor a comparator will give you analog output, because the sensor doesn't support this from the geginng..

you need to build you'r own sensor using a photodiode, phototransistor or LDR...

good luck

thanks
Ok, so does it means that IR sensors give Digital output ?
when i measured the O/P of IR detecter using voltmeter then there was very slow shift in voltage s
change shown by mutimeter..i mean , the voltmeter was showing a change from 0V to 4.66V when IR detecter was shifted from black to white tape.but the rate of change of voltage as seen on voltmeter was quite slower...
so the crux of whole text is that this slow transition (as shown by multimeter ) won,t work with uC(i suppose 'coz the response was toooo slow.). What do u say in this regard.

 

[Nigel Goodwin]

If you're using an IR receiver IC you need to send digital pulses of 38KHz IR, you can't send continuous 38KHz. The receiver strips off the 38KHz, and outputs a copy of the original digital data (although not a very accurate copy!).

 

[bhardu]

What !!!

If you're using an IR receiver IC you need to send digital pulses of 38KHz IR, you can't send continuous 38KHz. The receiver strips off the 38KHz, and outputs a copy of the original digital data (although not a very accurate copy!).

What ! IR receiver IC ???
no way i m using IR detecter(diode).& want to send that data of IR detecter to uC.
so my question is that do i need to interface a ADC in between the IR detecter and uC ?(so that IR detecter's O/P can be send to uC )

 

[AllVol]

when i measured the O/P of IR detecter using voltmeter then there was very slow shift in voltage s
change shown by mutimeter..

If you are using an analogue meter, one with a needle, quite naturally you will see a slow response time as the DeArsonval movement operates.

I am not a robot man, but from what I've read, I would expect there to be a grey area of transition anyway.

 

[bhardu]

If you are using an analogue meter, one with a needle, quite naturally you will see a slow response time as the DeArsonval movement operates.

I am not a robot man, but from what I've read, I would expect there to be a grey area of transition anyway.

im not usnig Analog voltmeter.it's a digital one .it takes nearly 10 sec for the value shown in display ot get stabilize.

 

[ikalogic]

What ! IR receiver IC ???
no way i m using IR detecter(diode).& want to send that data of IR detecter to uC.
so my question is that do i need to interface a ADC in between the IR detecter and uC ?(so that IR detecter's O/P can be send to uC )

have you read the datasheet?

look, i sware! you don't need an ADC with this IR receiver!

then, yes, it is an IR receiver IC, not a photodiode! (Again look at the datasheet) it hase a built in amplifier, comparator, demodulator.......

what you've experienced while transiting from a white to a black strip, is most probably due to the fact that some abiant light is refelecting on the white tape, and causing some noize to the output, but nothing 'digitally' important (only a couple of millivolts...)

see what i mean my firiend?

 

[audioguru]

Doesn't anybody read the datasheet?
The TSOP17xx receives data up to 2400 bps.

 

[ikalogic]

Doesn't anybody read the datasheet?
The TSOP17xx receives data up to 2400 bps.

Thanks for the back-up, finally!

 

[philba]

the tsop17xx output is pulled high internally so if you aren't seeing V+ with nothing being transmitted, something is wrong.

Things to consider:
- you are looking for reflected light (detect whether a line is under the receiver or not). If you haven't shielded the receiver from the transmitter, you will be measuring the direct light from transmitter.

- Maybe the transmitter is too strong and is reflecting off the black as well as light portions of the track. This would result is seeing a mostly low signal (but see the next item).

- as was said before, the tsop17xx wont receive a continuous carrier. YOu need to pulse the carrier - the datasheet tells you how long to wait between pulse bursts. page 5 of the datasheet shows this visually.

in general, you should learn how to read the datasheet and work through each possible problem methodically. I also recommend testing your circuits in a step-wise fashion. validate each section in turn. an O'scope would be a big aid to you right now.

while we are at it, look at the recommended circuit on the datasheet - make sure you have the bypass cap in place as noise can cause you a lot of grief in this case. I would also bypass the LED as well since that's adding to the noise of the system.