Radio Controlled LEDS?

[crazylegsmurphy]

Thanks Blue,

So, just so I fully understand. What I need is 3 IR LED's all with the widest range of possible frequencies (to avoid overlap), and then I need 2 receivers in each device to match, and pick up the frequencies from the other two?

Then the Microcontroller can check for both frequencies and if both present, light the lights?

Or will one IR receiver be able to pick up multiple frequencies, and can the controller still see both?

________

On a related question. How do universal remotes work? I know you program the remote with a key that then works with your TV. Could these devices use the same function?

For example, if I programmed the Microcontroller to have unique ID's...so all three devices had a unique ID, could the IR transfer that information to be picked up by the receiver microcontroller?

If this is possible, then I could just use one standard 40KHz IR LED and send the information instead of frequencies.

Universal Remote

 

[crazylegsmurphy]

Ok....Ok....


If you guys weren't frustrated with me before....then you soon will be. I for one am totally confused so I'm trying to take a step back and gather what I have learned so far.

The following are the two ideas I'm still holding on too.

1. Radio Signals:

How a Remote Entery Works

I know many of you have said that radio is directional, but I don't understand how my car door unlocker thingy can work in a parking lot, from like 50 feet away, through cars, concrete, and such.

It seems reasonable that I could have a radio signal strong enough to fo 1 foot and "see" a receiver is it not?



Could I not make a transmitter similar to a door locker, or garage door opener that would work over this short distance? Could I not limit the distance by using less power so it wouldn't work past 1 foot?


2. IR:

Universal remotes seem to have a very simple way of working.

Universal Remote

Basically it pulses out IR signals that the receiver turns into binary and the microcontroller tells the device what to do. To me, this seems like a simple solution of giving each device a unique ID that the microcontrollers can "see" and then say, (IF device 1, and device 2 (I'm device 3) are sending me their proper ID's, then I'll light my own lights.



So these are basically the only ideas that seem to hold any water at all (unless there is something that hasn't been suggested yet).

So, with that in mind, could we start fresh in a sense and work off the idea that one of these solutions might work?

I'm voting for RF myself (because of it being able to go through objects easier), but if anyone has anything to add, please feel free. I realize I'm starting to become a pain and such, but I really appreciate all your help, and I'm excited to see if I can get this working.

 

[arhi]

The resin in the pic looks much different then a bottle with marbles .. you have to remember few things, I tried with "full power" 40KHz modulated IR led, so you can do a simple test your self, put a new set of batteries in your remote control, put remote control inside/behind the resin, and try to change the tv channel .. pretty simple test you can do quite easy ... you can use phone camera to check if light is going trough the resin at all (phone cam will see the IR light) so you can check
- if IR light will go trough the resin (with camera)
- if signal carries by IR light will get distorted (if you change the channel, it will not be distorted)

As for the frequencies, you can either go with 3 far apart frequencies, note as blue already said IR receivers detect +-5KHz (some of them bit more, some bit less).. the other way you can go is to use same freq for all devices and transmit ID, then use uC to read the ID and you will know exactly what device is near you (so you will know when only one device is near by, and which one, and of course when both devices are near by)...

I'd make test with the remote control and resin before I continue to think about IR - in my experience, IR goes trough things i'd never believe it would, and does not pass trough things I'd say it would .. so - experiment is only way to go

on the RF topic .. RF is the way to ignore all the obstacles, problem is the distance, it is hard to control the distance especially with great accuracy (you said you need to detect 30cm - with 10% that is 3cm margin of error, as I previously said imho that is scifi)

one more note - pay attention that as batteries dry whatever you go with (IR or RF) your calibration will go with it, so if it worked 30cm with full batt pack, it might go 15 with batt pack on 80%... I'm with blue that reed relay and "ring magnet" is much easier

 

[crazylegsmurphy]

Sir, you have given me hope!

I'll try that test right away! If it works then we might just be golden!

You're a big help, I just wanna say that!

As for the RF...so...it seems that it would be good IF there was a way to let the device know where it was...is there any way to do a feedback signal, or some kind of signal strength detection?

You also mentioned "I'm with blue that reed relay and "ring magnet" is much easier"

Can you explain what these are, how they work and what the advantage would be?

I tried using rare earth magnets and they were super strong when connected, but didn't work at a distance greater than about 5 cm.

EDIT:

I was just looking at these: Mini RC cars

The spec sheet claims an eight-foot range. The most I got was six feet no matter how far I stayed from local interference.

How come these little things only have a range of 6 feet? What is limiting the range so much, and how can I limit it even more? There has to be a way to extend a radio signal with only enough strength to reach a foot or so....at this point, I don't even really care if it's a little more, or less....working is cooler than cool!

 

[Torben]

One thing to try for preserving power is to have the transmitting devices spend most of their time asleep, only waking up to transmit a signal. Of course the receivers will still need to be active the whole time. You should still be able to ping fairly quickly. Always-on realtime transmitting would chew power.

Would it be OK if the lights sort of smoothly rise as the devices approach each other, or should they suddenly switch on when a certain range is hit? I think something like RFID would be better for a sudden-switch situation and that maybe something like sampling the strength of a signal on a certain frequency might be better for the smooth closer-brighter idea. The smooth option will still have a pretty sharp distance relationship if the radiating antenna is somewhat omnidirectional because of the inverse-square law.


Torben

 

[crazylegsmurphy]

One thing to try is to have the transmitting devices spend most of their time asleep, only waking up to transmit a signal.

That would be perfect!

Would it be OK if the lights sort of smoothly rise as the devices approach each other,

If that could happen, I would be completely and totally happy! It's exactly what I wanted them to do, but was thinking I needed to have that done by the microcontroller.

heh heh...from then you lost me.

I need to read up on RFID....

So you're saying if I used a RFID, then it would be basically an "ON" "OFF", but if I used something to "test" the strength....what could do that...cause THAT sounds perfect to me!

EDIT:

If I'm getting you right....the receiver would basically have "steps" or something and notice when it hits a signal of a certain strength...if it detects that, it stays off, but as it gets closer it realizes the strength of the signal is coming with more intensity, so it starts to light up?

 

[Kryten]

A theoretically perfect isotropic radiator does that (Isotropic radiator - Wikipedia, the free encyclopedia ) but I don't think they can be built in practice. Antennas all have characteristic radiation patterns which are affected by the shape of the antenna and what is near them.

I have to say that i dont agree. There are several antennas that are omnidirectional that have spherical transmissions. think of walkitalkies (beeing a radioamateur i have made a couple of these antennas). If you use a GP (Gground Plane) antenna then you get full 360 deg and 180 deg vertical. But there can be issues with the power and where you put the antenna that can do stuff you havent anticipated.
The walkitalkies (and GPs) are just a vertical like the one on a RC controller, and my allegation is that they are "true" omnidirectional antennas.

 

[crazylegsmurphy]

That's kinda what I thought. I mean from what I know, those RC planes can fly around you in a circle and the antenna is just a metal stick basically.....if it were directional you really would have no chance flying the plane..

With my design, I could actually have an antenna run the entire length of the core, and even wrap around the core if I had too. If I can get an omnidirectional signal out of the antenna... then that's one awesome step forward!

 

[Torben]

That would be perfect!

Mmm...I hate to say it but the more I think about it, the less I think that idea would work with the rest of my idea.

If that could happen, I would be completely and totally happy! It's exactly what I wanted them to do, but was thinking I needed to have that done by the microcontroller.

heh heh...from then you lost me.

I need to read up on RFID....

So you're saying if I used a RFID, then it would be basically an "ON" "OFF", but if I used something to "test" the strength....what could do that...cause THAT sounds perfect to me!

EDIT:

If I'm getting you right....the receiver would basically have "steps" or something and notice when it hits a signal of a certain strength...if it detects that, it stays off, but as it gets closer it realizes the strength of the signal is coming with more intensity, so it starts to light up?

Various thoughts I'm having at the moment are:

A) The three devices could each emit a distinct tone on a given frequency, and their receivers would filter the received signal for a beat frequency which would activate the lights based on how strong the beat is (just a flight of fancy, somebody like RadioRon might help you there).

B) Each device would still have a distinct tone on a given frequency, but each device would filter the incoming signal for those frequencies and compare their relative amplitudes to values in a table indexed by frequency, lighting the LED only if 2 table frequency entries have amplitude values which are met (the receiving device is the 3rd device so it only needs to find 2 others nearby).

In all I think it could be an interesting but possibly fairly complex task.


Torben

 

[crazylegsmurphy]

In all I think it could be an interesting but possibly fairly complex task.

Well, at this point it seems like the options are getting thin, so if it's more complex than just a battery glued to a hunk of resin, then that is the direction I'm going to have to go.

Could it not work...where all three give out an RF signal. And each one tests the signal for strength as you said, ( received signal for a beat frequency which would activate the lights based on how strong the beat is ).

Now, that would mean that it wouldn't need two signals to light the lights, just the one...so if it were close enough it would check the following:

1. Is the signal strong enough
2. IF YES, then check for two RFID's
3. Are both ID's present, IF YES, light lights based on signal strength, IF NO, THEN loop until they're found.

It's taking me a bit to grasp your idea...but I think I may be following you.

I think perhaps we may be onto something.

Please keep mulling this over everyone, I'm kinda following along, then going and reading all I can find to help it make sense.

 

[Torben]

I have to say that i dont agree. There are several antennas that are omnidirectional that have spherical transmissions. think of walkitalkies (beeing a radioamateur i have made a couple of these antennas). If you use a GP (Gground Plane) antenna then you get full 360 deg and 180 deg vertical. But there can be issues with the power and where you put the antenna that can do stuff you havent anticipated.

Only approximately. Up and down are still a problem. The radiation pattern is more toroidal than spherical. I don't think a true spherical radiator is really possible to build.

The walkitalkies (and GPs) are just a vertical like the one on a RC controller, and my allegation is that they are "true" omnidirectional antennas.

Only in 2D. I bet if you took two of those units and pointed the antennas at each other you'd lose range, compared to having the antennas parallel.


Torben

 

[crazylegsmurphy]

Up and down are still a problem.

But in this case, if we think of my project devices as basically like...a rounded cone sitting on a table, the up/down really isn't an issue as the other devices will more than likely be brought together at an angle parallel to each other....like three upside down drinking glasses sitting beside each other...with an antenna directly up the center of each.

 

[Kryten]

Well Torben isent the point here to "see" when a device is in range? with antennas you can get the device to fade the light on as the signal increses.

Only approximately. Up and down are still a problem. The radiation pattern is more toroidal than spherical. I don't think a true spherical radiator is really possible to build.

Im not shure what you men by up and down (but if i get it you mean the vertical line of the antenna) and by the way the down will bw limitet by the ground plane. There will of course be a littel cone going from the antenna, whit the center in the vertical (follow the length of the antenna) line and going on for ever. but from my experience with radios (espcialy handhels units) you can get a nice signal even if you point the antennas at each other (tip to tip)

 

[crazylegsmurphy]

There will of course be a littel cone going from the antenna,

I'm no expert, but I am sure there are dead spots above and below, but as Kryten said, the ground eliminates one of them, and the top...well, in this case, it's not a big deal as they're not going to be "stacked" on top of each other. If I can get an 80 radius out of the antenna..with the majority of the signal in a 360 degree radius out from the center of the device, then that gets the ol' thumbs up from me.

So....lets see here. Are we perhaps under the agreement that this may work with this method?

 

[Torben]

Well Torben isent the point here to "see" when a device is in range? with antennas you can get the device to fade the light on as the signal increses.

Yes, I agree, and I said that too.

Im not shure what you men by up and down (but if i get it you mean the vertical line of the antenna) and by the way the down will bw limitet by the ground plane. There will of course be a littel cone going from the antenna, whit the center in the vertical (follow the length of the antenna) line and going on for ever. but from my experience with radios (espcialy handhels units) you can get a nice signal even if you point the antennas at each other (tip to tip)

Earlier you said that a spherical radiator can be built this way, yet above you describe a non-spherical radiator.

It would probably be fine for the purpose but I am simply not going to agree that a fat toroid with a flat bottom is a sphere.


Torben

 

[Torben]

I'm no expert, but I am sure there are dead spots above and below, but as Kryten said, the ground eliminates one of them, and the top...well, in this case, it's not a big deal as they're not going to be "stacked" on top of each other. If I can get an 80 radius out of the antenna..with the majority of the signal in a 360 degree radius out from the center of the device, then that gets the ol' thumbs up from me.

So....lets see here. Are we perhaps under the agreement that this may work with this method?

Like I said to Kryten, I agree that it would probably be fine for your purposes. The radiation pattern isn't quite spherical so you might notice some range issues if the devices were, say, laid on their sides, but I don't think those range problems would be any worse than what you might get from other environmental factors anyway.


Torben

 

[arhi]

crazylegsmurphy, reed relay will "on/off" depending on magnet near it (the idea is to use it as a switch "actor" will use when he want to turn them on ... does not go with your requirement (detect proximity) ..

as for the RF .. torben, I'm not sure that on 30cm distance "radial vs toroidal" would make much difference .. if it was 30m then it would be much more important ... for 30cm, I believe the whole different problem's arise.. how to detect signal strength with few cm precision .. it should be possible but .. someone very good with RF should try to make some test .. I tried some simple test and I was not able to make difference with 1m precision (ok, I know I do not have a clue about RF)

 

[Torben]

as for the RF .. torben, I'm not sure that on 30cm distance "radial vs toroidal" would make much difference .. if it was 30m then it would be much more important ... for 30cm, I believe the whole different problem's arise..

Hi arhi,

Yes, I as I earlier agreed, I don't think the difference is so important for this application--but that's not the same thing as stating that the difference does not exist.


Torben

 

[crazylegsmurphy]

crazylegsmurphy, reed relay will "on/off" depending on magnet near it (the idea is to use it as a switch "actor" will use when he want to turn them on ... does not go with your requirement (detect proximity) ..

Right, right. I did a bit of research and from my experience magnets just don't have the distance needed to work in this application. As I said, I used rare earth magnets in my initial low tech test, and while the magnets have 30 pounds of pull, they have almost no distance (less that 4 cm).

how to detect signal strength with few cm precision

I think (If I'm keep up with you guys) is that we all agree that in theory this may work. The issue is really the ability of the receiver to detect the signal strength given off by the (very limited distance) transmitter.

There also seems there may be some small issue with the actual pattern of the signal, but for this purpose it doesn't seem to be likely it'll effect it much.

So...with that said then....I suppose this is where I am at.

I got a friend to try changing his channels on his TV with his remote pointed through the exact type of resin, and I am getting another friend to try as well. The only thing that didn't work was when he tried changing the channel through about 8 inches of resin, from 3 meters away.

I think with the information I have from you guys here, and the tests done with IR, it might be worth starting some practical tests to see how they work in the real world and then choose the best from the two.

The question then is...(and if you guys weren't frustrated with me before, you soon will be) where do we start?

Keeping in mind that this needs to stay small, and needs to use relatively low power consumption, I have found the following schematics as a start. If you guys don't mind taking a look, could you let me know what I might need to look at to get the two working as discussed.

1. RF

Simple FM Transmitter

FM Transmitter Links

**broken link removed**

2. IR

IR Transmitter

IR schematic Links

Now, by no means to I expect anyone here to do this for me. I am fully prepared to do my homework and try to fully understand this. I am new at this, but I'm determined to get it working.

So, all I am looking for is your guys' help to point me in the right direction so I'm not all over the place, or working on something that's not applicable to this project. I'll do my research, get the stuff and do test after test, show you my progress and try to stay out of your hair as much as I can.

I really appreciate your help everyone!

 

[crazylegsmurphy]

Hey,

Here are my updated notes from the research I did today. Sorry if it's long, I tried to break it down by sections.

So, the next step (since I have no chance of randomly designing my own), is to find very simple schematics and then modifying them to get the effect I'm going for. This is where it gets out of the "Will it work?" and into the "How to make it work?"

From what I understand, I am going to need the following for each device.

- Transmitter
- Receiver
- MCU
- Battery(s)
- LED's

- IR LED's & Antenna

Here is what I found in my looking around:

______________________________________________

1. RF

Transmitter:

Simple FM Transmitter - FM Transmitter

VERY simple FM transmitter - http://www.pcs-electronics.com/schematics/7413.jpg

FM Transmitter Links - ePanorama.net - Links

Requirements:

- If any of these will work, then I need to figure out where to hook up the MCU.
- I also need to find a way to limit the RF range either manually (resistors or something), or via a tuner of some sort.
- Need to be able to tune the devices to different frequencies, or send ID's using the MCU on one frequency (I think that would be the best IMO)

Receiver:

- Very simple FM receiver - **broken link removed**

- Super Simple FM receiver - FM Crystal Radio

- Receiver Links - ePanorama.net - Links

Requirements:

- Need to figure out a way for the receiver to read the signal strength so the LED's light up as the signal gets stronger (devices get closer)
- Need to be able to "catch" either two frequencies or ID's from MCU
- Need to figure out where to hoop up a MCU

______________________________________________

2. IR

Transmitter:

- IR transmitter - http://www.electronic-circuits-diagrams.com/alarmsimages/19.gif

- IR Links - ePanorama.net - Links

Requirements:

- Same as above...need to figure out where to hook up MCU
- Need to decide if it's going to send frequencies or ID's from the MCU on one frequency

Receiver:

- Not sure if this would work - Build a Simple InfraRed Remote Control

- Another? - **broken link removed**

Requirements:

- Need to be able to hook up MCU
- Must find a way for the IR receiver to know when the other devices are within 1 foot so they then turn on.
- Need to decide if I'm going to use 3 frequencies or and ID sent by the MCU
- Need MCU to recognize either 3 frequencies, or ID's

______________________________________________

3. Other requirements

- Would love to have the LED's fade in as the devices get closer
- Would like the LED's to all fade from bright to dim randomly when devices are together
- Would like to add an optional universal power adapter ( **broken link removed** ) plug.
- It would be awesome if the devices "slept" when not in use and were woken up by either vibration, or signal change detection.
- Need to determine the best batteries to use for maximum usage.

______________________________________________

Heheh, I know that seems like a lot, but that's basically the list I have here at home of things I need to figure out. I need to first pick a few schematics that will work, then redraw them to include the parts I need. Once I get that, I'm going to order the parts and get to trying to make them.

As for the programming....well, at this point I may pay someone to do it for me if I can't find any sites that have programs already made that I can learn from.

So...if you don't mind taking a look at what I posted and making suggestions, or if you have links to better schematics that would be great too. As I said, I don't need you to do this for me, just get me started in the right direction.

Awesome! Thanks!