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Infra Red oscillator

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dark

Member
Hello Forum,

I dont have experience wit IR communication . I am employing it in an automotive application BUS Transit . I intend to communicate directionaly the status of fuel/coolent inside the BUS from side ways through fixed transponders .

The Bus may be at 60Km/H speed but distance is less 2meter . Is it possible to collect data at this speed with IR system? . The data being 6 digit number. I am unable to use RF as it isnt directional and will confuse between two Buses as the onboard transmitters will always be in ON state working as simplex configuration to cut the time required in protocol exchange. Also from so many Buses it would also be difficuly for RF fixed transponder to maintain a search and slave enumiration .

I see a lot of circuits employing 555 timer and RC oscillators for carrier generation. I feel these arent that precise as the ceramic resonator isnt there . Is it ok to use 555 or RC oscillator for this much distance ? . I plan for 38KHz carrier frequency. How can we generate 38KHz precisely for this application ?


Please advise.

Regards

PS: there is already too much load on my MCU that it wouldnt be possible to generate 38KHz .
 
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Mikebits

Well-Known Member
Are you saying you wish to relay engine coolent information via a 555 timer? How exactly would you do this?

Post a drawing of what you propose, I am sure this would help in clarifying your misconceptions.
 

dark

Member
Are you saying you wish to relay engine coolent information via a 555 timer? How exactly would you do this?

Post a drawing of what you propose, I am sure this would help in clarifying your misconceptions.
Actually what I am asking is regarding the stable 'Infrared carrier generator ' and does a 555 timer fits the industrial application bill? or a XTAL controlled is required?.
Is it be possible to relay the information from a moving vehicle to a wayside transponder using Infrared serial link , I mean It takes less time for the vehicle directional link to passby the fixed transponder(receiver) . Drawing I tried to explain here;


Now as it can ve seen in the drawing the transmitter stays in contact with the receiver for a small time , hence can we transmit the desired information that quickly. The vehicle may be moving at more lower speeds say 20Km/Hr.

Thanks
 

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crutschow

Well-Known Member
Most Helpful Member
You might read http://www.electro-tech-online.com/custompdfs/2009/03/AN1016-DPDF.pdf for some info on IR data transmission.

You need to decide how the data will be encoded and the precision (number of bits) you need for the fuel and temperature information.

At 20Km/Hr the bus would be moving at 5.6 meters/sec or 180ms/meter. Thus you would have 180ms to read the data if you assume you can read it during the time the bus moves 1 meter, which should be more the sufficient. You could send the info in RS-232 serial port format, which should be fast enough and which many microprocessors can support. A microprocessor typically operates with a clock crystal that precisely generates the transmission frequencies.

You could send the info as one sync byte (say all 1s), one or two fuel bytes, and one or two temperature bytes. You continually resend this sequence.
 

Sceadwian

Banned
This is an out-doors application so you're gonna want some really bright IR LED's for transmission, and a solid receiver setup. The receiver is going to potentially need to deal with near saturation conditions (sun shining at it) and still be able to detect the paltry output of an IR LED.
 

crutschow

Well-Known Member
Most Helpful Member
This is an out-doors application so you're gonna want some really bright IR LED's for transmission, and a solid receiver setup. The receiver is going to potentially need to deal with near saturation conditions (sun shining at it) and still be able to detect the paltry output of an IR LED.
Along with that, a lens in front of the detector to limit the view angle, as well as an IR (pass) filter to block out visible light, will likely also be needed.
 

Sceadwian

Banned
If the source is modulated and it's output is controlled into a good beam the receiver optics won't matter much, in fact you'll want as wide a viewing angle as possible, or you can 'lean' to avoid shots. If the gun transmits something like an address at the carrier frequency (who is shooting) and the senders lasers is well focused all you need to do is have the receiver require a certain number of packets (100ms's worth maybe) to get a 'good' shot. Ideally you'd want at least two receivers, front and back, maybe one on each shoulder that require a slightly longer reception pattern.

You can think of it this way. Unless you're a sniper and that does not really come into play here, you're going to shoot a target down with multiple rounds. Your receiver starts to beep the instant it detects another gun firing within a lethal pattern, giving you time to react or take cover, a few interrupts will reset the 'kill' counter. Too long in the kill zone and you get flagged with a death. Given the known acuracy/reliablity statistics you can find on modern fire arms and you could replicate the kill probability of any fire arm. Even if the user had no recoil and a scope =)
 
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dark

Member
Hi, Thanks for the replies,

Daylight will definitely induce problems ? I am thinking about Ultrasonic transducer ,is it possible to use one ? does anyone knows a water proof Ultrasonic transducer not an open frame one!.

Thanks
 

Roff

Well-Known Member
If the source is modulated and it's output is controlled into a good beam the receiver optics won't matter much, in fact you'll want as wide a viewing angle as possible, or you can 'lean' to avoid shots. If the gun transmits something like an address at the carrier frequency (who is shooting) and the senders lasers is well focused all you need to do is have the receiver require a certain number of packets (100ms's worth maybe) to get a 'good' shot. Ideally you'd want at least two receivers, front and back, maybe one on each shoulder that require a slightly longer reception pattern.

You can think of it this way. Unless you're a sniper and that does not really come into play here, you're going to shoot a target down with multiple rounds. Your receiver starts to beep the instant it detects another gun firing within a lethal pattern, giving you time to react or take cover, a few interrupts will reset the 'kill' counter. Too long in the kill zone and you get flagged with a death. Given the known acuracy/reliablity statistics you can find on modern fire arms and you could replicate the kill probability of any fire arm. Even if the user had no recoil and a scope =)
Are you replying to a different thread? You are talking about shooting, and the OP is talking about a bus.:confused::confused::confused:
 

ericgibbs

Well-Known Member
Most Helpful Member
Hi, Thanks for the replies,

Daylight will definitely induce problems ? I am thinking about Ultrasonic transducer ,is it possible to use one ? does anyone knows a water proof Ultrasonic transducer not an open frame one!.

Thanks
hi,
The IR method was used/tried on London transport buses about 25 years ago.
On some of the pavement poles they mounted IR scanners, on the bus side they had retroprism flat reflectors.
The idea the scanners detected the bus ID and the location of the poles, the data was sent by radio to a central control, this way they had a good idea where the buses where..

Its now been surpassed with RF technology.

Ref, the ultra sound, at speed or in a wind the ultra sound beam will get 'blown' away...that is bent away from the detector.

Also the data transfer rates will not be as high as IR could be.

OK.?
 

Sceadwian

Banned
Sorry about that, I have no idea how I cross posted that reply. That was a reply to someone asking about a laser tag marking system.
 

dark

Member
hi,

Eric so the possiblity of Ultrasonic is ruled out too ! . This didnt come to my mind , the wind gusts could also be a problem . As you say IR has been tried and changed over to RF therefore IR shouldnt be tried I think there must be some shortcomming in it which will become evident in trials .

Now again the last option left is RF . Ok then but in that case how can we make the transmition beacon small and directional say If we choose a 433MHz transmitter with 10mW power. I am aware of a Pi atteunation network but what exactly should be done to atteunate the signal to a desired level . Earlier I have been only amplifying the power it as much as possible : ) .

I think I would require a beacon about about 4meter in length and a spread of2meter maximum? to avoide crosstalk .


Thanks
 

ericgibbs

Well-Known Member
Most Helpful Member
hi,
I think I would require a beacon about about 4meter in length and a spread of2meter maximum? to avoide crosstalk .
Thanks
Why would you think a 'beacon' of this size is required when using a low power system.?

Where do you expect the crosstalk to come from.??
 

Sceadwian

Banned
In the US. At least in my city the local fire/police department use IR modules on traffic lights to control them. So it's not been given up on completely.
 

dark

Member
Why would you think a 'beacon' of this size is required when using a low power system.?

Where do you expect the crosstalk to come from.??
Because there could be more than one slaves and I couldnt enumirate them due to huge number of slaves out there . The wayside detector will not know which slave is around and which not.

If the beam is focused the crosstalk will be less and same addressing can be kept.

Regarding IR again , does this requires a very stable oscillator ? hopefully a XTAL controlled . Are you talking about these prisms " reflector prism-Large Photo & Picture "

Eric ,Do you have link to London Bus IR equipments .

carl said:
At 20Km/Hr the bus would be moving at 5.6 meters/sec or 180ms/meter. Thus you would have 180ms to read the data if you assume you can read it during the time the bus moves 1 meter, which should be more the sufficient. You could send the info in RS-232 serial port format, which should be fast enough and which many microprocessors can support. A microprocessor typically operates with a clock crystal that precisely generates the transmission frequencies.

You could send the info as one sync byte (say all 1s), one or two fuel bytes, and one or two temperature bytes. You continually resend this sequence.
Thanks Carl, but I ask about IR carrier frequency generators , stablity . As I dont feel like using a 555 timer for tempco and other stability issues. And how to deal with near saturation issues , if the receiver is pointing horizontly towards a bus then there is no question of sunlight entering it as from 2-5 meters distance the Bus body will block it .

Thanks
 

ericgibbs

Well-Known Member
Most Helpful Member
hi,
If I went the IR route I would consider using a PIC with an inbuilt UART.

Program the PIC with the bus ID, use the PIC's adc/etc for data capture, transmit the data via the UART thru an IR link.
 

dark

Member
hi,
If I went the IR route I would consider using a PIC with an inbuilt UART.

Program the PIC with the bus ID, use the PIC's adc/etc for data capture, transmit the data via the UART thru an IR link.
I understand what you mean , the MCU timer will take care of carrier frequency. I think the IR will not work in FOG / SNOW and Rainy season what do you think am I over cautious ? or switch over to RF .

Also will it be possible to represent this carrier modulated Frequency 40KHz via MAX485 at transmitting side where we can finally buffer this with a power amplifer LM380 or alike .

Thanks
 
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ericgibbs

Well-Known Member
Most Helpful Member
I understand what you mean , the MCU timer will take care of carrier frequency. I think the IR will not work in FOG / SNOW and Rainy season what do you think am I over cautious ? or switch over to RF .

Also will it be possible to represent this carrier modulated Frequency 40KHz via MAX485 at transmitting side where we can finally buffer this with a power amplifer LM380 or alike .

Thanks
You can also RF for RS232 data type transmission, TX/RX modules to do this already exist.

Can you say why its required to capture this bus data.?
 

dark

Member
You can also RF for RS232 data type transmission, TX/RX modules to do this already exist.

Can you say why its required to capture this bus data.?
Eric , The problem here is I require low cost directional and RFID type of solution for that I require to reduce the power of RF transmitter which I am not sure , I think its time to start a new thread now as this thas nothing to do with IR anymore.
Thank you all for your help If you have time please do followup my other thread ;

RF power atteunation - Electronic Circuits Projects Diagrams Free

Thanks
 
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