Help on infrared remote control, 38khz quarz

[[email protected]]

Hi folks,
I have to build an infrared remote for a school assignment. I've found
this website and I think it's the only one that gives pretty clear
instructions on what to buy, etc.

http://www.boondog.com/tutorials/lrir/mc145026.htm

(Of course I'd be happy to know if there are any better ones you know)
Well, my question is whether there is any way to avoid putting a 38 kHz
quartz in there, because they seem to be extremely hard to get,
especially in Germany, where I happen to live. I mean...there are so
many remotes being built, so it seems improbable that they all have
those rare components inside them, right? So how could I change the
schematics so that I don't need that quartz or any other rare
components, without having to change too much of the other stuff?

I hope some of you guys can help me on this one. My problem is that I'm
completely clueless when it comes to electronics and still I'm supposed
to build this remote plus receiver within a few weeks.

Greetings,
M. Seifert

 

[Norm Dresner]

Hi folks,
I have to build an infrared remote for a school assignment. I've found
this website and I think it's the only one that gives pretty clear
instructions on what to buy, etc.

http://www.boondog.com/tutorials/lrir/mc145026.htm

(Of course I'd be happy to know if there are any better ones you know)
Well, my question is whether there is any way to avoid putting a 38 kHz
quartz in there, because they seem to be extremely hard to get,
especially in Germany, where I happen to live. I mean...there are so
many remotes being built, so it seems improbable that they all have
those rare components inside them, right? So how could I change the
schematics so that I don't need that quartz or any other rare
components, without having to change too much of the other stuff?

The web page explicitly says
"The good news is that they still carry other frequency models. For
example, there is the 38.0 kHz model (Jameco Part #131908) and the 37.9 kHz
model (Jameco Part #139889). You can use either IR module and buy a matching
crystal (Digikey carries them). The schematic is identical."

so there's nothing magic about 38 KHz. If you can find parts for any other
frequency, you can use them instead. I have a vague recollection that
something in the neighborhood of 42-44 KHz is more commonly used in
commercial TV stuff.

Norm

 

[[email protected]]

(Of course I'd be happy to know if there are any better ones you know)
Well, my question is whether there is any way to avoid putting a 38 kHz
quartz in there, because they seem to be extremely hard to get,

They're not extremely hard to get - take apart practically any
TV/VCR/DVD/universal remote control and you'll find a crystal (actually
a ceramic resonator) of approximately this frequency.

 

[Tim Shoppa]

Most of remotes use a RC oscillator of some kind to set the frequency.
You will note that the tutorial example circuit uses a quartz for the
transmitter but a RC for the receiver.

Many homebrew microprocessor-based IR remote projects use a
microprocessor clocked in the MHz range and divide down (often in
software delay loops) to get to the actual data rate.

If you want to use a crystal in the transmitter, go ahead and use a
32.768 kHz crystal and modify the RC constant in the receiver
appropriately.

Tim.

 

[[email protected]]

Most of remotes use a RC oscillator of some kind to set the frequency.

Most [infra-red] remotes use a ceramic resonator to set the frequency.

 

[[email protected]]

Yeah well I read what the website says, but the problem is that there
is no German electronics company that sells ANYTHING near that range.
The only crystals they have are xx MHz, not kHz. If I look for crystals
in some old TV remotes, I'll probably find crystals, but I don't know
what frequency they are...besides the fact that I don't even have an
idea what a crystal looks like.

But thanks for all the responses so far anyway.

Greetings

 

[Deefoo]

Hi folks,
I have to build an infrared remote for a school assignment. I've found
this website and I think it's the only one that gives pretty clear
instructions on what to buy, etc.

http://www.boondog.com/tutorials/lrir/mc145026.htm

(Of course I'd be happy to know if there are any better ones you know)
Well, my question is whether there is any way to avoid putting a 38 kHz
quartz in there, because they seem to be extremely hard to get,
especially in Germany, where I happen to live. I mean...there are so
many remotes being built, so it seems improbable that they all have
those rare components inside them, right? So how could I change the
schematics so that I don't need that quartz or any other rare
components, without having to change too much of the other stuff?

I hope some of you guys can help me on this one. My problem is that I'm
completely clueless when it comes to electronics and still I'm supposed
to build this remote plus receiver within a few weeks.

Greetings,
M. Seifert

First of all your link does not work (try
http://boondog.com/\tutorials/lrir/mc145026.htm ) and second they use a xtal
of 32.768 kHz which is not rare at all.

-- DF

 

[John Popelish]

Hi folks,
I have to build an infrared remote for a school assignment. I've found
this website and I think it's the only one that gives pretty clear
instructions on what to buy, etc.

http://www.boondog.com/tutorials/lrir/mc145026.htm

(Of course I'd be happy to know if there are any better ones you know)
Well, my question is whether there is any way to avoid putting a 38 kHz
quartz in there, because they seem to be extremely hard to get,
especially in Germany, where I happen to live. I mean...there are so
many remotes being built, so it seems improbable that they all have
those rare components inside them, right? So how could I change the
schematics so that I don't need that quartz or any other rare
components, without having to change too much of the other stuff?

I hope some of you guys can help me on this one. My problem is that I'm
completely clueless when it comes to electronics and still I'm supposed
to build this remote plus receiver within a few weeks.

A crystal may not at all be necessary. The receiver contains a band
pass filter that is not crystal based, and con pass a band of
frequencies that is nominally centered around the specified frequency.
For a single unit (not production) you can make a clock with an
LMC555 timer, and adjust it to approximately the correct frequency by
experiment. Find the highest frequency that works, the lowest that
works, and set it to about the middle of that range.

 

[Michael Black]

They're not extremely hard to get - take apart practically any
TV/VCR/DVD/universal remote control and you'll find a crystal (actually
a ceramic resonator) of approximately this frequency.

Not the ones I've taken apart. Maybe it's changed with more recent
ones, but the ones I've seen use a higher frequency ceramic resonator,
around 450KHz is one that comes to mind.

I'm not sure why something would be using a 38KHz crystal. One reason
you see more crystals in consumer electronics than thirty years ago is
because once things went digital, it was easy to toss an extra divider
into an IC, so cheap crystals could be used, no matter what the frequency
that was needed. ANd the lower the frequency, the bigger and more
expensive the crystal.

Michael

 

[Michael Black]

Yeah well I read what the website says, but the problem is that there
is no German electronics company that sells ANYTHING near that range.
The only crystals they have are xx MHz, not kHz. If I look for crystals
in some old TV remotes, I'll probably find crystals, but I don't know
what frequency they are...besides the fact that I don't even have an
idea what a crystal looks like.

Then get a crystal oscillator, or a crystal and build an oscillator, and
then add a divider to get it down to where the circuit needs it. So
you pick a cheap available crystal, making sure it divides down evenly
to the frequency you need (or maybe not, depending on how precise the
frequency in your application must be), and making sure you can do it
with the amount of division available in a cheap and common divider.

Michael

 

[[email protected]]

Well thanks, that sounds like it could work. The only problem is, I
hate to say this, but I have no clue on how to build something like
this, so if you happen to know any knowledge source where I could find
some guides on this, I'd be happy to know. I have this book, "The Art
of Electronics" by Horowitz and Hill, but I haven't read it. Maybe you
could tell me if there's something in it that could help me.

Max

 

[Spehro Pefhany]

Most of remotes use a RC oscillator of some kind to set the frequency.

Most [infra-red] remotes use a ceramic resonator to set the frequency.

Usually in approximately the AM radio IF (~455kHz) frequency range,
IIRC. That's used for the clock of a microcontroller etc.


Best regards,
Spehro Pefhany

 

[[email protected]]

Not the ones I've taken apart. Maybe it's changed with more recent
ones, but the ones I've seen use a higher frequency ceramic resonator,
around 450KHz is one that comes to mind.

Sorry, you're right - I'm on crack. I didn't realize you needed an xtal
to provide the actual carrier frequency, I thought you were using a
cookbook/appnote circuit around one of the usual suspects for IR Tx.
Normally the carrier is generated by a [masked] microcontroller which
is clocked by something rather faster - as you observed

 

[Pooh Bear]

Hi folks,
I have to build an infrared remote for a school assignment. I've found
this website and I think it's the only one that gives pretty clear
instructions on what to buy, etc.

http://www.boondog.com/tutorials/lrir/mc145026.htm

(Of course I'd be happy to know if there are any better ones you know)
Well, my question is whether there is any way to avoid putting a 38 kHz
quartz in there,

It says 32.768kHz actually.

A standard 'watch crytal'.

£0.44 from Farnell.

http://uk.farnell.com/jsp/endecaSearch/searchPage2.jsp?Ntt=32.768khz&Nty=1&N=401&Ntk=gensearch




Graham

 

[Frank Bemelman]

It says 32.768kHz actually.

A standard 'watch crytal'.

The website also says:
******
Updated Note (02/27/99): The 32.7 kHz IR module was originally carried by
Jameco (part #106382), but was sadly discontinued.

The good news is that they still carry other frequency models. For example,
there is the 38.0 kHz model (Jameco Part #131908) and the 37.9 kHz model
(Jameco Part #139889). You can use either IR module and buy a matching
crystal (Digikey carries them). The schematic is identical.
******

 

[[email protected]]

Yeah...too bad you can't get any of those in Germany without paying
huge shipping fees and probably waiting weeks for it to arrive...

 

[Jasen Betts]

Hi folks,
I have to build an infrared remote for a school assignment. I've found
this website and I think it's the only one that gives pretty clear
instructions on what to buy, etc.

http://www.boondog.com/tutorials/lrir/mc145026.htm

(Of course I'd be happy to know if there are any better ones you know)
Well, my question is whether there is any way to avoid putting a 38 kHz
quartz in there, because they seem to be extremely hard to get,
especially in Germany, where I happen to live. I mean...there are so
many remotes being built, so it seems improbable that they all have
those rare components inside them, right?

use a 38kHz resonator instead

Jaycar lists 38kHz crystals in their catalogue (jaycar.com.au)
and they don't have an exhaustive range by any means.
There's bound to be a supplier closer to you that has them.
start with "electronic components" (or equivalent) in the yellow pages.

 

[Kryten]

Well thanks, that sounds like it could work. The only problem is, I
hate to say this, but I have no clue on how to build something like
this, so if you happen to know any knowledge source where I could find
some guides on this, I'd be happy to know.

Hi Flashbiter.

You really need to at least have a clue of how to find out how to solve the
problem,

I have this book, "The Art of Electronics" by Horowitz and Hill,

An excellent first move.

but I haven't read it.

Aha, I think you can spot the problem here

Maybe you
could tell me if there's something in it that could help me.

It is a good book that will guide you into the subject but it has no
circuits for what you wish to do.


http://www.howell1964.freeserve.co.uk/remotes/index_handsets.htm
http://www.howell1964.freeserve.co.uk/remotes/irrc_systems.htm

Carriers vary from 32 to 39 kHz.
36 kHz is a good frequency in the middle of this range.
Dividing a cheap TV colour carrier crystal should give adequate carriers
14318181 Hz / 400 =
3579545 Hz / 100 = 35.79545 kHz

 

[Pooh Bear]

Yeah...too bad you can't get any of those in Germany without paying
huge shipping fees and probably waiting weeks for it to arrive...

You said you were *building* one. So what's wrong with using a
32.768kHz crystal ?

Graham

 

[Bob Monsen]

You said you were *building* one. So what's wrong with using a
32.768kHz crystal ?

If the OP is using one of those integrated infrared receivers, he should
note that they have filters in them. I'm thinking of the TSOP11xx parts.
For example, if he has a TSOP1138 it'll attenuate much of the signal at
32kHz. delta f(3dB) = f0/7, so it'll filter out half the power at
32.758kHz.

---
Regards,
Bob Monsen

The question of the ultimate foundations and the ultimate meaning of
mathematics remains open; we do not know in what direction it will find its
final solution or even whether a final objective answer can be expected at
all. "Mathematizing" may well be a creative activity of man, like language
or music, of primary originality, whose historical decisions defy complete
objective rationalization.
- Hermann Weyl in 1944