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IR (Almost) Universal Signal Repeater
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IR (Almost) Universal Signal Repeater

by Snipeye on Wed Jul 14, 2010 4:11 pm

So, I have a little remote for a camera, but the range sucks, maybe 10 feet max. I was going to open it up and put a couple nicer IR led's in, but then I came up with a better idea: A (semi)universal repeater.

Here's what I was thinking, though I have no clue how actually possible it is:

Put it in front of the IR-emitting device, and it will read the signal with 2 photoresistors to get a cleaner signal, then emit it again. Here's the catch: It operates anywhere in the 30-50 kHz range. If the device operates at 35 kHz, this detects it, and when it sends the signal out again (with nicer IR LED's for improved range/signal) it oscillates at 35kHz.

Seeing as I haven't don a whole ton of electronics, and I've done nothing with IR, I'm at a loss at to where to start. Anybody willing to help out?
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Re: IR (Almost) Universal Signal Repeater

by Entropy on Wed Jul 14, 2010 4:58 pm

If you configure it to eliminate ambient light sources (e.g. sensor clips to the IR signal source), you could just make a repeater using some logic buffer circuits. So whatever frequency the input was blinking at would be transferred to the output.
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Re: IR (Almost) Universal Signal Repeater

by uoip on Wed Jul 14, 2010 5:13 pm

Try a web search on "infrared repeater". If you include terms like "smarthome" or "pyramid", you may find various sources of items. There are lots of commercial devices. I also found this site describing a home-brew solution, and it has some nice technical details: http://www.cedarnet.org/smartware/Hardware/IR_Repeater/

My general rule of thumb is that, if an electronic product is widely available commercially and if it comes pretty close to meeting my needs out of the box, then my build/buy decision starts leaning pretty strongly toward "buy". I'm unlikely to be able to build something that's much better or cheaper than what's commercially available, even if what's commercially available is somewhat overpriced and somewhat mediocre quality. So personally, I'd probably buy something, but don't let that discourage you from attempting the educational and potentially fun satisfying experience of designing and building your own device.
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Re: IR (Almost) Universal Signal Repeater

by oPossum on Wed Jul 14, 2010 5:34 pm

This circuit uses an ordinary IR LED as an IR detector. It must be carefully aligned with the IR LED in the remote because it isn't very sensitive. Each IR pulse is amplified, so the carrier frequency will be accurately reproduced.

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Re: IR (Almost) Universal Signal Repeater

by Snipeye on Wed Jul 14, 2010 6:38 pm

And which LED is being used as the receiver? Is there a different IR led I could use for it so I don't have to align it 'very carefully'?
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Re: IR (Almost) Universal Signal Repeater

by Entropy on Thu Jul 15, 2010 10:03 am

Snipeye wrote:And which LED is being used as the receiver? Is there a different IR led I could use for it so I don't have to align it 'very carefully'?

Probably a phototransistor with some support electronics (opamps?) would be more sensitive.

However, there is still the problem of ambient light. If you don't do carrier filtering (e.g. something like a bandpass filter centered around 38 kHz or so, with enough bandwidth to handle other carrier frequencies), ambient light will get repeated too if it's bright enough. So it's a lot easier if you mechanically bind the sensor to the transmitting device.
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Re: IR (Almost) Universal Signal Repeater

by Snipeye on Thu Jul 15, 2010 11:40 am

I know, but that would sort of ruin the entire 'universal' part of it. I figure I'll put a developed negative over it to let IR through, and put a switch on it so it only transmits when I want it to. However, I have found another design (thanks to the help of another forum) and I need some opinions.

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Re: IR (Almost) Universal Signal Repeater

by oPossum on Thu Jul 15, 2010 12:13 pm

Snipeye wrote:And which LED is being used as the receiver? Is there a different IR led I could use for it so I don't have to align it 'very carefully'?


LED1 is the detector, LED2 and LED3 are the emitters. The IR LED is most sensitive around 950 nm and is quite directional, so no filtering of ambient light is necessary. The limited sensitivity prevents latch-up that would occur if the detector was triggered by one of the emitters. Using a PNP to amplify the detector output, and two NPN to drive the emitters provides high gain so there will be a significant boost in IR output (assuming the source is a single relatively weak LED).

A QSE159 is a sensitive IR detector that could be used, but it could cause problems with latch-up and ambient light sensitivity. Good layout an shielding would be critical.
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Re: IR (Almost) Universal Signal Repeater

by oPossum on Thu Jul 15, 2010 12:22 pm

Snipeye wrote:I know, but that would sort of ruin the entire 'universal' part of it. I figure I'll put a developed negative over it to let IR through, and put a switch on it so it only transmits when I want it to. However, I have found another design (thanks to the help of another forum) and I need some opinions.

Image


The LED current is limited to about 70 mA with a fresh battery. I am not sure there is enough gain in the circuit to even get 70 mA. Most remotes drive the IR LED with hundreds of mA, so there would likely be a reduction in IR output. Using a 9V battery for a single IR LED is inefficient. LEDs are current driven, not voltage driven, so the lowest practical voltage will be most efficient.

The QSC114 is a narrow angle (+/- 10 deg) IR phototransistor. Careful alignment is required, no shielding is needed.
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Re: IR (Almost) Universal Signal Repeater

by Snipeye on Thu Jul 15, 2010 1:30 pm

Alright, I'll be going with your design, then. How long do you think the battery life would be, and could it use rechargeable batteries, or would the voltage be too low?
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Re: IR (Almost) Universal Signal Repeater

by Snipeye on Thu Jul 15, 2010 6:09 pm

Sorry for the double post - I'm doing a mass order from digikey soon, and that particular model of IR LED wasn't there... do you think this would work alright as a substitute?

http://search.digikey.com/scripts/DkSea ... 11-1365-ND
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Re: IR (Almost) Universal Signal Repeater

by oPossum on Thu Jul 15, 2010 6:38 pm

Digikey has the TSAL6200 (tinted version of the TSAL7200).

Battery life depends upon usage. Rechargeable is fine, but many rechargeable batteries have high self-discharge rates, so they won't last long even with little usage. The latest NiMH, like Eneloop, claim to have very low self-discharge.
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Re: IR (Almost) Universal Signal Repeater

by richms on Sat Jul 17, 2010 6:17 am

The commercially available wireless repeaters and some wired ones use an integrated ID photodiode and filter and demodulator, then transport the demodulated signal and have a modulator at the other end. When you are sticking the LED onto the device you are controlling like with cable boxes etc then the carrier is much less important. The one for all wireless one i have does have a screw on it to change the carrier, but it works on most things fine from about 1/4 to 3/4 on the trimpot.

The other option depending on how many buttons the camera remote has on it, would be to get a keychain wireless RF remote and hook the outputs to the buttons on the cameras IR remote.

I had a universal keychain remote for TVs that had crap range, it used a 2032 coin cell. I tried 2 2016's stacked in it thinking it would either work or blow it up, and it worked and the range was slightly better. Not much tho. If the remote is cheap then perhaps try over volting it if replacing it is really cheap.

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Re: IR (Almost) Universal Signal Repeater

by Snipeye on Sun Aug 22, 2010 8:56 pm

Sorry to necro this, but I'm finally getting time to actually work on it - which, unfortunately for you guys, means I'll be asking a lot more questions. :D

So, I'm new to eagle, and I'm starting with a schematic, but I can't find the right part for just about anything in the libraries I have. Where can I download the libraries I need to make the schematic, then board? I've looked at the cadsoft site that has some user uploads, but I can't seem to find what I need there either.

Long story short, where can I download the libraries I need?
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Re: IR (Almost) Universal Signal Repeater

by Snipeye on Mon Aug 23, 2010 5:48 pm

Sorry for the double post, but I have an update:

I was successful with the schematic, and I've designed the board the size of a AA battery, so I can place it in a AA holder with 3 other batteries - enclosure and power. :D

Here's the board, I'd appreciate it if you guys would take a look and offer suggestions. Because I'm going to be etching it myself, I don't want to do double-sided.

EDIT: I updated the board, I no longer get any errors (beside 'part x has no value!') in eagle with the checker-thing.
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Updated Board!
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