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Author Topic: So... How is it exactly with remote control by IR?  (Read 1925 times)
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Siepraw, PL
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Hi.

I see multiple topics on this, but there are some things I just don't get smiley

First of all: all I want to make is a little device, which can "record" IR code and then "play" it.

So I got one IR diode and one IR photodiode.

I assume buying the photodiode was a mistake? Or maybe I can connect it to work as "normal" IR receiver? If not, which one of these should I buy?

And... if not, then what is the IR photodiode used for, in general?

Next thing - IR codes/protocols.
As I can see, there almost as many IR transmission protocols, as the devices which use them smiley But AFAIR my PDA was able to collect IR code from any remote.
So am I wrong, or the "recording" is just checking whether the IR beam is coming (1) or not (0) with some frequency? If so, what frequency should be good to check signals coming from normal TV or camera remote?

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I'd probably go for the IRM 8510. (the other two look like they operate at too low frequencies).

The problem with a plain photodiode is that the codes are sent as short bursts of around 38kHz pulses. The photodiode will see these, but won't demodulate them.
The IR receivers do the demodulation for you, so all you hgave to deal with is the much lower frequenc pulses representing the code.

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I've done some experiments with IR recorders, and those 'proper' IR remote control receiver chips.

Some of those IR RC receivers are very 'smart', and don't start to follow the modulation of the incoming IR signal for several cycles. So what you record may be a few cycles short in every pulse. For any specific device, this should be pretty consistent, so you can probably correct for it.

The second issue is they are deliberately made to respond to a fairly narrow range of modulation frequency, so modulation which is +/- 2 KHz will usually be picked up, but further away and it might ignore it.

The problem with an ordinary photodiode is the signal might be a bit small, and hence needs amplification. Some folks use fast photo transistors which give bigger signals, but are a bit slower than a photodiode. Remember you just need a logic HIGH or LOW, so it isn't an analog input your looking for.

HTH
GB

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'Proper' IR RC receivers are quite sophisticated devices.

They pass through the modulated signal if they determine that it is within the parameters of the specific device. Some, such as specific noise-rejecting Vishay devices, won't start to follow the received signal for as many as 10 cycles.

They help by ignoring signals which are not modulated within their sensitive frequency band.

They also have automatic gain control, so that the signal looks like a nice clean square wave across a wide range of actual detected signal strengths.

Both these behaviours are significant work to engineer, but, you can reduce the benefit of the automatic gain control by training the 'learner' with the IR transmitter at a fixed distance about, 0.5m, and tweaking the electronics.

A plausible alternative, which I believe I have seen, but can't google up again, and I have never experimented with, is to get several IR RC receivers with, e.g. 4 KHz separating them, for a wide range of sensitivity.

HTH
GB
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Ooops, forgt to answer

Quote
And... if not, then what is the IR photodiode used for, in general?
That IR photo diode appears to be an IR RC receiver, and not an ordinary photodiode
http://sklep.monster.pl/SFH-06-36-36kHz-ODB-PODCZ(4,36348,30962).aspx
It appears to be a 36KHz IR RC receiver, but I can't find it anywhere with an English language (or any language) datasheet.

Often, SFH99 format part numbers are Osram, e.g. opto semiconductors, but I looked here, and couldn't see any SFH06's

Normal photodiodes can used for these sort of applications, but very often for high-speed IR comms because they can respond to megahertz, gigahertz (or even higher) signals.

GB
« Last Edit: April 22, 2010, 03:13:29 pm by gbulmer » Logged

Siepraw, PL
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I assumed it is an ordinary photodiode (two legs? receiver? photodiode! smiley-grin), but yes, there is mention about 36kHz. The problem is the shop don't have any datasheet for that part. Yes, I asked them smiley

So is there any "universal" way to check what can it do, or give it a break and buy normal IR receiver?

P.S. Thanks to all for the replies.
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Yes, sorry you are correct, I can only see two wires. I wonder what it is. I assume it is a photodiode, in which case the 36KHz is a bit weird.
Datasheets are always worth having smiley

Wire it up like a photodiode, and wave an Infrared Remote in front of it.

Here's an example http://www.repairfaq.org/sam/samschem.htm#schir1
You should be able to power that from 5V (instead of 9V), and maybe use a smaller resistor than 500 ohm, e.g. 270

and here is a thread, with some more useful links: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1242217035

Once you've figured out that it works, then connect the "Scope monitor point" to an Arduino digital pin, and you have your ITR detector.
Used the Arduino for timing it.

HTH
GB
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Quote
So is there any "universal" way to check what can it do

Maybe - if you have an oscilloscope handy...
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http://www.arcfn.com/2009/08/multi-protocol-infrared-remote-library.html

This is a pretty good piece of code for capturing IR signals.

http://zovirl.com/2008/11/12/building-a-universal-remote-with-an-arduino/

This is a decent explanation of how IR works, in general.

=) I just started messing with this stuff a few weeks ago, don't worry it's pretty easy to pick up.
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This project is a learning remote control based on an ATmega168:
http://www.lochraster.org/unzap/?en

There hardware and code are available at that link.

[edit]There are some more useful links at
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1270451288[/edit]
« Last Edit: April 23, 2010, 06:47:31 pm by gbulmer » Logged

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Back in the win95/98 days I made an IR control recorder/player that attached to the parallel port. Extremely simple with a IR photo transistor for recording, and an IR LED for transmitting. There was a simple program that would record and also playback the recorded codes. When XP came along, the timing was lost due to the time sharing in XP. An extensive google search might turn up the site if it still exist. Today one might or make a gizmo like below. If one doesn't mind some small soldering, one can hack a $5 universal IR remote control so one can control the button pushes on it.

http://www.usbuirt.com/order.htm
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$50 for a http://www.usbuirt.com/order.htm !!!

The unzap http://www.lochraster.org/unzap/?en uses an ATmega48/168, and is only 30 euro for a kit, which suggest the parts beyond an Arduino are about 10 euro.
The code is Open Source, the schematic is Open Source.
If you don't want the large data flash for recorded codes, it's even less money, WRonX already has some of the parts, and only needs one, $1-ish part and some resistors to get going.
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Below is the link to the IR gizmo I made many years ago. The software is still there with the source code that may help duplicating efforts on an arduino. Bottom pix are of tinkering with IR remote control so I could do a channel up button via the computer. The chips in the remote controls are connected to the buttons which are in a ~6x7 matrix. A $4.95 universal remote control at WalMart has a chip in it that is precoded for hundreds if not thousands of remote controls.

http://www.ziplabel.com/cir/schem.html




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Siepraw, PL
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You guys are great smiley

I had a couple of days offline (I've got a son! smiley-grin ), and I got so many replies. Since I've got less time now, I'll try it and let you know when I'll be able to. Thanks!
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