Infrared Transmitter & Receiver

Trying to figure out which IR module to get...

I have a drone that operates on 2 ir channels 38KHz or 57KHz. If I make a beacon / transmitter pair and it is set to 38KHz will it interfere with drone commands even if the beacon pulses at a different rate than the drone controls?

I did a test recently with a 38kHz TSOP receiver and sent it signals at different carrier frequencies.

Wasn't an exhaustive test, but the 38kHz receiver was happy with carriers between 35 and 40kHz, but didn't work at 30 and 45kHz. I didn't have the energy to narrow it down any better than that.

So there is clearly some leeway around the nominal carrier frequency, but I'd be inclined to think that 38 and 57kHz are far enough apart for them not to interfere.

There's only one way to be really sure I suppose, and that's to test it?

(kHz by the way, not KHz.... 8) )

There are both 940nm and 850nm 38khz units out there.
This will be another thing to take into account.

JimboZA:
There's only one way to be really sure I suppose, and that's to test it?

So here is a similar setup to what I will be using, but instead 5 IR LED's. This will be my emitter.

Let me see if understand you correctly...
a 38kHz receiver will still be able to pickup a signal between 35kHz & 45kHz - I understand that. So now if I have my emitter set up with a 555 timer emitting a 38kHz square wave I believe that is the same wave that would be communicating with my drone. But I guess if it isn't sending a viable header and command it shouldn't have any effect on it?

For the emitter would I be able to just use the 555 timer to constantly send out a 38kHz square wave and call it a day? I just don't want this to effect my ability to control the drone. Maybe I just need to operate the drone on Channel B

LarryD:
There are both 940nm and 850nm 38khz units out there.
This will be another thing to take into account.

I purchased this IR Diode pair so I'm not sure what what wavelength they operate on. How could that affect me?

In general, I am still a bit hazy on IR communication and how things work with square waves - correct me if I am wrong, but this is how I believe the commands are sent to my drone: The IR Emitter is pulsed on and off at frequency of 38kHz. i.e. the pulse would be low for 1500us and high for 500us etc. and that is how you would basically send your 0 and 1.

That cct should be modified a bit.
Each IR led should have it's own series resistor.
Do not parallel LEDs.

You key the LEDs at 38kHz then not key the LEDs at all.

Here is an example:

.

If your emitters are 850nm and the drone receiver is 940nm, things will will fail.
If however the you use your match pairs you should have no problems.

adjit:
In general, I am still a bit hazy on IR communication and how things work with square waves

Have a look at my ramble tutorial here; it includes using a 555 to do this. Two of them in fact: I used one to create the 38kHz carrier, and then switched that 555 off and on with another one, to create an actual message.

LarryD:
That cct should be modified a bit.
Each IR led should have it's own series resistor.
Do not parallel LEDs.

You key the LEDs at 38kHz then not key the LEDs at all.

cct? Not sure what you mean by that.

Why should I not parallel the LED's on the emitter? I want them all to do the same thing. I am working based off of this page and they had stated that with the LEDs in parallel they didn't stretch as far because they weren't drawing enough current. Therefore, they were in the process of testing using an NPN transistor, which would draw more power from the battery, however it would power the LED's better.

Do you have an example circuit of the way that you would wire it up that I could look at?

Also, I'm pretty sure this schematic is wrong:

If the LEDs are diodes, then according to this diagram they shouldn't be emitting when the output pulse is sent out of 3. It looks like the way they have it is if the switch is open the current flows to the diodes and towards the output pin (3).

LarryD:
If your emitters are 850nm and the drone receiver is 940nm, things will will fail.
If however the you use your match pairs you should have no problems.

Would there be a way to test this? or just trial and error?

Thanks for the work Jim.

adjit:
cct? Not sure what you mean by that.

Abbreviation for "circuit"

LarryD:
Thanks for the work Jim.

If you look at the dates you'll see I was bored over the Christmas holiday... I'd appreciate any comments.

Just so we are on the same track, you plan to use your new IR LEDs to transmit data to an existing receiver on your drone, is this correct?

If you look at the dates you'll see I was bored over the Christmas holiday... I'd appreciate any comments.

I will look at it in depth tomorrow, 10:50pm here.

Why should I not parallel the LED's on the emitter?

You cannot guarantee that current will equally divide in paralleled LEDs as their forward voltages are not identical.
If you place a series resistor for each LED and then place these in parallel, current will then flow equally in all the LEDs.
Your driver would have to be able to sink the total current for the 5 IR LEDs.

LarryD:
Just so we are on the same track, you plan to use your new IR LEDs to transmit data to an existing receiver on your drone, is this correct?

Ok here is my setup to clarify things a bit.

The drone receives commands from an LED transmitter at 38kHz - I am using my Arduino to send these commands. This will be separate from my emitter/receiver pair - this will act as a beacon/tracker.

On the drone I will have IR receiver modules pointing in different directions to pick up the IR beacon signal and determine which way it came from.

On the ground I will have my IR beacon/emitter, again pointing in multiple directions. My plan was to use the 555 timer and just have the emitter constantly emitting a 38kHz signal.

Jim, skimmed your ramble and there is some good info in there 8)
Just need to spend some time figuring it all out. It's 1am here so can't really spend too much time on it now. Will try and read it more extensively on saturday when I have some time and actual IR receivers/modules to test with.

LarryD:
If you place a series resistor for each LED and then place these in parallel, current will then flow equally in all the LEDs.
Your driver would have to be able to sink the total current for the 5 IR LEDs.

That makes sense.

But what do you mean by driver? Again - any chance you can show me a quick circuit of how you would set it up? Still working on mine - but when I get it figured out I will post it

Also, was I right about that circuit I showed earlier being wrong? or at least something doesn't look right there.

Do you have any idea what the part number is for the IR LED?
You need to know what the forward recommended current is.

Unsure... this is the transmitter/receiver pair I purchased. The only thing I have been able to find is that one of the comments says it requires at least 220ohm resistor. I guess when I get the LEDs I can just use an ohmmeter to figure that out

If I understand you:
You will be making two circuits, one to control the drone (controlled by an Arduino on the ground) and a second to receive a constant beacon powered by a driver like a 555 timer circuit on the ground.
Both are at the same light frequency and both at 38kHz.
The receivers are in the drone and the transmitters are on the ground.

I assume you want to use the IR pairs for both circuits from your link you attached.

If that's the case the two circuits will receive each others information and will collide.

I would recommend you to use 850nm for one and 940nm for the other.
This way the light frequencies are different and not interfere with each other.

Next if this is outside the ambient light may and probably will saturate your receivers.

The best I have been able to do with what looks similar to your IR pairs is 40 feet indoors with one IR transmitting led.