PDA

View Full Version : VR IN 67 ZX-IRM 38kHz IR receiver



Pimpom
06-23-2010, 03:43 PM
Does anyone have more details about the VR IN 67 ZX-IRM 38kHz IR receiver module offered by Vega Robokit?
http://tinyurl.com/32zhulp

What I'd like to know is -
1. If it's suitable for continuous 38kHz pulses, unlike common remote control receivers which need discontinuous IR pulses.
2. If the sensitivity (and therefore range) is comparable to popular modules like the TSOP1738.

Thanks in advance for any input.

pratheek
06-23-2010, 06:18 PM
Have your tried asking vegakit?

Pimpom
06-24-2010, 01:20 PM
No. I thought of asking for forum members' personal experience because, having been in electronics for a long long time in a remote corner of the country, most of my attempts to get information from Indian shops and companies have been exercises in futility.

There have been a few exceptions, but most of the time, emails are simply ignored. It's not just about technical information. Enquiries about availability, prices, shipping, payment, etc simply remain unanswered 9 times out of 10. Even when they do reply, the points raised are usually not clarified. On the phone, what they say or promise often turn out to be unreliable. All of this is in complete contrast to my experience with foreign firms.

OK. Anyway, I'll ask Vegakit.

MohitM
06-24-2010, 05:13 PM
No. I thought of asking for forum members' personal experience because, having been in electronics for a long long time in a remote corner of the country, most of my attempts to get information from Indian shops and companies have been exercises in futility. ...<snip>... All of this is in complete contrast to my experience with foreign firms.
There is a simple reason... Tech/sales support costs money. This adds to the product cost. Compare Indian prices to foreign prices, don't add customs and freight. You'll find a huge difference in the prices of the same product. LM7805 on www.digikey.com for 1000 pieces is $ 0.241 (~ Rs. 11.00). You should get the same brand (National or Fairchild) for < Rs. 5.00 in Delhi/Mumbai.

In fact, within Indian companies, you can see the difference. If you talk to a sales staff at Silicon Components, they'll help you make a component selection, point to datasheets, samples etc. Whereas if you talk to Cirkit Electro or others at Lamington Road, they will give you the stock position and price but hardly help you with a selection, part-alternatives, etc. Their support site is located at www.google.com. :-) Parts from Silicon Components in most cases costs 20% more than what Cirkit quotes. I have a comparative quotation which shows this for a fact. F.e. LM7805 for 250 pcs is Rs. 6.00 at Silicon and Rs. 4.9 from Cirkit.

Pimpom
06-24-2010, 10:33 PM
I'm afraid I have to disagree. Please read my post again. The vast majority of enquiries I send to shops and companies are purchase questions, not requests for technical support. Most of my questions are in effect things like "Do you have items XYZ?", "How much?", "How do you want the payment sent?". How do they expect to sell things if they don't answer questions like that?

If some shops are interested only in over-the-counter sales, fine. It's their choice. But my enquiries are to those who tout their goods on the internet, publishing their email addresses, inviting enquiries and telling everyone what good service they provide.

I've dealt with foreign firms of all levels - one-man shows, small businesses, medium-sized ones and large corporations. 95% of all correspondences are answered promptly, courteously and to the point. They are not all large companies with high overheads and an army of highly paid staff.

You mentioned Cirkit. I've visited Bombay/Mumbai several times over the past 20 years, sometimes staying for weeks. I've been into most of the shops on Lamington Road, Proctor Road, Chunam Lane, Kiln Lane, Tara Temple Lane, etc. I've visited and bought from Cirkit a number of times. But none of the emails I sent them received a reply.

docel
06-24-2010, 10:57 PM
Ok - this is veering Off-Topic !
Did you ask Google?
If you don't get any datasheet/information then why buy it ?
Have you bought this board/ module ?

Pimpom
06-24-2010, 11:52 PM
Ok - this is veering Off-Topic !
Sorry about that. I was letting off some steam after some 40 years of pent-up frustration.

Did you ask Google?
Yes. No luck. The part in question does not seem to be a product of some large manufacturer. There's one similar to it, but not quite the same.

If you don't get any datasheet/information then why buy it ?
Because I have not found a suitable one so far. All the readily available IR Rx modules I know of are not completely satisfactory as they require discontinuous pulses which slow down response times. I've used the available ones with a "make" response time of a few microseconds which is more than good enough. But I'd like to improve on the "break" response time which cannot be reduced to much below 1 millisec because of the minimum gap time between bursts.

The alternative would be to design the receiver from scratch. But I need to send the IR beam over a large distance, and it will involve a fairly complex circuit for amplification, AGC, noise supression, etc. This is an important but one-off project and I'd like to avoid all the extra work if possible.

Have you bought this board/ module ?
No.

docel
06-25-2010, 01:09 AM
I don't think you asked Google politely.... :D I found quite a few pages ......!

All IRMs have a specific purpose- to detect the 'wanted' signal & reject the unwanted (spurious signal).

There is a difference between a IR diode and and IR module.
The Ir diode is just that - a simple PN junction diode responding to the IR spectrum of light.
This does not differentiate your source from other sources.

The IR Module is more complex. It responds to IR light Modulated at some Specific Frequency.
The 38Khz IRM does just that: It has a sunlight filter, Responds ONLY to IR light switched 38,000 times per sec.
The Module has several units inside.
One is the AGC . controlled by the filter output
2nd is a Band pass filter- This responds to 38khz center frequency IR pulses and controls the AGC.
3rd Integrator- produces a steadily changing output voltage for a constant input voltage.

"The distinguishing mark between data signal and
disturbance signal are carrier frequency, burst length
and duty cycle." is what the Datasheet says.

So, a constant 38khz signal will be detected at low gain ( low sensitivity ), a 38khz signal chopped ( Modulated ) 10times per second at high gain (hi sensitivity).

A continuous 38khz will actually be rejected by the IRM by design.

A 'burst' with a specific duty cycle will be accepted and passed on to the output.

The remote control signal is a pulse train of several bits that must have a specified duty cycle and time for good response.

All this means there is no way an IRM can do your job as specified by you.

Pimpom
06-25-2010, 04:41 AM
I don't think you asked Google politely.... :D I found quite a few pages ......!
Of the particular module in question? If so, do you mind sharing the URLs?
Or do you mean IRMs in general? If that, then I have dozens of datasheets of modules by Vishay, Sharp, Panasonic, etc.


All IRMs have a specific purpose- to detect the 'wanted' signal & reject the unwanted (spurious signal).

There is a difference between a IR diode and and IR module.
The Ir diode is just that - a simple PN junction diode responding to the IR spectrum of light.
This does not differentiate your source from other sources.

The IR Module is more complex. It responds to IR light Modulated at some Specific Frequency.
All of this is quite elementary and should be known to everyone except a novice on the subject. However.........


The 38Khz IRM does just that: It has a sunlight filter, Responds ONLY to IR light switched 38,000 times per sec.
Not quite. The module still responds to some extent to sunlight, incandescent light bulbs, etc. It's why I usually shield my modules with opaque material.


The Module has several units inside.
One is the AGC . controlled by the filter output
2nd is a Band pass filter- This responds to 38khz center frequency IR pulses and controls the AGC.
3rd Integrator- produces a steadily changing output voltage for a constant input voltage.

"The distinguishing mark between data signal and
disturbance signal are carrier frequency, burst length
and duty cycle." is what the Datasheet says.
Basic characteristics common to all standard IRMs. I was simply wondering if some manufacturer made a non-standard module that responds to continuous 38kHz pulses or one that requires only a short gap between bursts.


So, a constant 38khz signal will be detected at low gain ( low sensitivity ), a 38khz signal chopped ( Modulated ) 10times per second at high gain (hi sensitivity).
Not necessarily 10Hz. In past projects, I successfully used much higher chopping frequencies (>1kHz), but I'd like to go still higher. I usually lock my chopping frequency to the carrier frequency so that the former is an integral sub-multiple of the latter.


A continuous 38khz will actually be rejected by the IRM by design.

A 'burst' with a specific duty cycle will be accepted and passed on to the output.

The remote control signal is a pulse train of several bits that must have a specified duty cycle and time for good response.
True. And different models have different specs for duty cycle.


All this means there is no way an IRM can do your job as specified by you.
As I said before, I was wondering if there was some non-standard module with less stringent requirements for burst cycles.

docel
06-25-2010, 07:33 AM
Your last post reminds me of a few things:

I have always suspected that too much knowledge is a dangerous thing. It is a boon to people who don't have deep feelings; their pleasure comes from what they know. . . . But this only emphasizes the difference between the artist and the scholar.

http://thinkexist.com/i/sq/as2.gif Margaret Anderson quotes (http://thinkexist.com/quotes/margaret_anderson/)

http://forum.canibus-infinity.com/viewtopic.php?f=60&p=8609

http://scienceblogs.com/principles/2010/01/a_lot_of_knowledge_is_a_danger.php?utm_source=feed burner&utm_medium=feed&utm_campaign=Feed%3A+scienceblogs%2Funcertainprinc iples+%28Uncertain+Principles

You seem to be quite knowledgeable, really ! And you have missed the answer to your query.

Then, isn't it a little superfluous of you to be
wondering if there was some non-standard module with less stringent requirements for burst cycles.

Your quest for a non-professional component is quite preposterous indeed. Do you expect any manufacturer to make anything that is 'non-standard' or ' less stringent' as you put it ? :D
Its up to you now, to decide whether you're a Scholar or an Artist !

Good luck :rolleyes:

allbits
06-25-2010, 11:09 AM
Not quite. The module still responds to some extent to sunlight, incandescent light bulbs, etc. It's why I usually shield my modules with opaque material.

If that is the case, then the module you have is exactly what you are looking for !! It must be less stringent, and non -standard.

Pimpom
06-25-2010, 02:54 PM
[B][COLOR=Blue]Your quest for a non-professional component is quite preposterous indeed. Do you expect any manufacturer to make anything that is 'non-standard' or ' less stringent' as you put it ? :D
Non-standard is not the same as non-professional. Non-standard here simply means something that does not conform to the most widely used specifications. Manufacturers do make those - like screws with a counter-clockwise thread, to name just one example.

CW threads probably account for at least 99.999999% of all screws used in the world, and a lot of people may be unaware that CCW screws exist. But they do exist and they serve a very useful purpose.

Other examples are pots with reverse-log taper, 56kHz IRMs, products where a 555 is not used as a timer...... The list is endless.


Its up to you now, to decide whether you're a Scholar or an Artist !
You've got me pegged backwards. A scholar learns and accepts what others have done. An artist strives to create something, often exploring unconventional methods. (BTW, I am an amateur artist, musician (used to have a rock band), photographer (I'm in the process of writing a book on photography), and I still occasionally play football, TT, badminton and basketball :))

I've worked with a lot of Indian engineers. Their most glaring shortcoming is an inability to look beyond convention and common practice.

allbits
06-26-2010, 03:00 PM
I've worked with a lot of Indian engineers. Their most glaring shortcoming is an inability to look beyond convention and common practice.

Not true.
May be the people who you have worked with were the conventional.

As for your query, it will be a good idea to buy the module and see. But when I look at it, Rs.176 for an IRM is a bit too costly.
There is not link for any datasheet, so I will suggest you request the guy for a datasheet (I understand fro your post that you have not done it yet.), if not buy it.
And if you have a specific application where you need to detect a modulated wave, use 567. (Just get out of the conventional IR modules !! :) )

allbits
06-26-2010, 03:14 PM
well.. to add on:
I could not find the product at the Inex site :http://www.inexglobal.com/products.php?type=addon
I think they no longer manufacture them.

but i found it here:
http://www.robotshop.ca/inex-38khz-infrared-receiver-4.html
and at a couple of other sites. They use a vishay sensor, and I think it will only detect bursts. Well, Rs 176 looks cheaper compared to the prices in USD.

Pimpom
06-28-2010, 12:02 AM
Thanks for your continued interest.

Not true.
May be the people who you have worked with were the conventional.
OK. Let's drop that side of the discussion for the time being, shall we?


As for your query, it will be a good idea to buy the module and see. But when I look at it, Rs.176 for an IRM is a bit too costly.
Yes, it's certainly too costly for a standard IRM. If it had happened to be an unconventional one that met my requirement, I was willing to pay the price. And that's the whole point of this thread. But it's apparently just another TSOP mounted in a box with a connector.

There is not link for any datasheet, so I will suggest you request the guy for a datasheet (I understand fro your post that you have not done it yet.), if not buy it.
And if you have a specific application where you need to detect a modulated wave, use 567. (Just get out of the conventional IR modules !! :) )
Ah, but whatever approach I use to modulate and demodulate a signal, I'm committed to sending it by IR beam. So, in order to achieve a fast reaction speed, designing and building my own IR receiver seems unavoidable.

The best reaction time I could get with my previous design was about 1.5 msec. I've thought of a way to get this down to about 0.7 msec with what's still a fairly simple circuit at the Rx side, using a conventional IRM. Some digital tweaking at the Tx side can get it down to 0.4 or 0.5 msec. This is acceptable, but I'd like to be able to at least halve that figure while using a readymade receiver module.

docel
06-28-2010, 05:30 PM
So, in order to achieve a fast reaction speed, designing and building my own IR receiver seems unavoidable.

That's when you'll become an Artist :D
I think what you need is a simple high current pulsed IR LED and Photo-diode receiver that is managed by some slick software.
There are other components and techniques too, for the speeds that you're talking about.
Anyway, we don't know anything about your application and suggesting alternatives will simply result in long and irrelevant posts of arguments and hitherto undisclosed necessities or discrepancies.

I don't see the need for those reaction times in a general application. In which case cost & complexity shouldn't matter at all.