Inexperienced and need to find/design 2ch remote control+audio receiver combo

[Steve Bergman]

Hi,

I'm not sure this is the right place to ask this, and pointers to the
appropriate place would be appreciated.

I'm a programmer, not an expert in matters RF. But due to factors
beyond my control, I have been called upon to make some decisions about
the design of a device because "I'm a technical guy". ;-)

The device would be worn like a name tag (which limits the size,
obviously. Perhaps 10cm x10cm x 3cm maximum) and be issued upon entry
to a public place. For example, a
shopping mall. It would be battery powered and need to be able to
receive and play voice quality audio. I would need a range of at
least a few hundred feet. (The transmitter can be off the shelf and
just needs to accept audio input from any standard "line out" from,
say, a CD player.) It also would have a separate receiver (from a
separate transmitter) for remote control of an LED.

I'm looking for some basic info like what broadcast type (AM, FM) and
frequency would be appropriate (and legal) for this use.

I believe that something like 418MHz or 434MHz AM would be appropriate
for the remote control part. But I'm really clueless regarding the
audio. I'm trying to avoid doing something really stupid like using
49MHz and having walkie-talkie's cutting into the broadcast.

Also, I would need some sort of protection against malicious
individuals cutting into the broadcast with their own transmitters.
This is difficult, as I need to be able to send audio and activate the
remote controls on all the tags simultaneously. So I can't use any
sort of rolling code protection. A fixed code is the best I can think
of. For the remote control, I've found a transmitter receiver pair
based on the Ming tws-434 and rws-434 chips with a fixed security code
that looks usable.

An all in one board that had the 2 channel remote and audio receiver
all together in either kit or preassembled form would be a godsend.

Again, apologies if this is not the appropriate group, but I am out of
my depth and would really appreciate some pointers.

Thanks for any enlightenment,
Steve

 

[Phil Allison]

** Desperate Code Scribbling Groper Alert

I'm not sure this is the right place to ask this, and pointers to the
appropriate place would be appreciated.

** Don't tempt me........

I'm a programmer, not an expert in matters RF.

** Then go to someone who damn well is.

Explain your loopy app and wanted specs to him.

Have a bank loan ready to pay for the design and development costs.

Off shore manufacture needs to be looked at.




........ Phil

 

[Frank Raffaeli]

Hi,

I'm not sure this is the right place to ask this, and pointers to the
appropriate place would be appreciated.

I'm a programmer, not an expert in matters RF. But due to factors
beyond my control, I have been called upon to make some decisions about
the design of a device because "I'm a technical guy". ;-)

The device would be worn like a name tag (which limits the size,
obviously. Perhaps 10cm x10cm x 3cm maximum) and be issued upon entry
to a public place. For example, a
shopping mall. It would be battery powered and need to be able to
receive and play voice quality audio. I would need a range of at
least a few hundred feet. (The transmitter can be off the shelf and
just needs to accept audio input from any standard "line out" from,
say, a CD player.) It also would have a separate receiver (from a
separate transmitter) for remote control of an LED.

I'm looking for some basic info like what broadcast type (AM, FM) and
frequency would be appropriate (and legal) for this use.

I believe that something like 418MHz or 434MHz AM would be appropriate
for the remote control part. But I'm really clueless regarding the
audio. I'm trying to avoid doing something really stupid like using
49MHz and having walkie-talkie's cutting into the broadcast.

Also, I would need some sort of protection against malicious
individuals cutting into the broadcast with their own transmitters.
This is difficult, as I need to be able to send audio and activate the
remote controls on all the tags simultaneously. So I can't use any
sort of rolling code protection. A fixed code is the best I can think
of. For the remote control, I've found a transmitter receiver pair
based on the Ming tws-434 and rws-434 chips with a fixed security code
that looks usable.

An all in one board that had the 2 channel remote and audio receiver
all together in either kit or preassembled form would be a godsend.

Again, apologies if this is not the appropriate group, but I am out of
my depth and would really appreciate some pointers.

Thanks for any enlightenment,
Steve

For un-licensed operation, the 418 and 434 MHz freqencies in the U.S.
are for remote control purposes only. The signal must be manually
actuated and must be intermittent, not contnuous, e.g. garage door
opener, tire pressure monitor, keyless entry ... to name a few
applications. Encoded voice may be transmitted in the ISM bands, e.g.
915, 2450, 5800 MHz. WCS bands may be used depending upon the
aplication.

Aside from that, to achieve several hundred feet (or more) range in a
shopping mall using a low-power (<1mW) transmitter and a small or
built-in antenna is feasible, but you will need a better link and
modulation method than what you describe. I don't know of any
off-the-shelf solutions that will give coverage you require with
reasonable quality. A custom solution may work.

More details on the application are required.

Frank Raffaeli
http://www.aomwireless.com/

 

[Phil Allison]

"Frank Raffaeli"

Encoded voice may be transmitted in the ISM bands, e.g.
915, 2450, 5800 MHz. WCS bands may be used depending upon the
aplication.

** Like "spread spectrum" or "DECT " cordless phones do.

Aside from that, to achieve several hundred feet (or more) range in a
shopping mall using a low-power (<1mW) transmitter and a small or
built-in antenna is feasible,

** Huh ??

A cordless phone could not reliably do that and they use much more than 1
mW.

but you will need a better link and
modulation method than what you describe. I don't know of any
off-the-shelf solutions that will give coverage you require with
reasonable quality. A custom solution may work.

** See my post for that line of thought.

More details on the application are required.

** But don't expect credible ones from the OP.

He is not the organ grinder, just the code scribbler.




........ Phil

 

[Frank Raffaeli]

"Frank Raffaeli"


A cordless phone could not reliably do that and they use much more than 1
mW.

indeed. You're right about DECT. However, other commercial methods are
superior. SS phones and DECT have little or no process gain. Also, I'm
presuming some infrastructure: repeaters, etc ... and assuming the OP
is limited to low power. It's not a trivial task. It also depends upon
what the OP means by "voice quality", and the expectations of
reliability.

Frank

 

[Phil Allison]

"Frank Raffaeli"
"Phil Allison""

indeed. You're right about DECT. However, other commercial methods are
superior. SS phones and DECT have little or no process gain.

** But have other nice advantages.

Also, I'm
presuming some infrastructure: repeaters, etc ..

** I think that is a bit too much to presume from folk so naive they gave
this task to a "programmer".

It's not a trivial task.

** Amen to that.


BTW:

Wonder if a GIANT audio induction loop might just do what the OP actually
needs.

Need more details to say.



........ Phil

 

[Steve Bergman]

Thank you, Frank, for your helpful post. This all just landed on me
the other day, and in addition to the technical matters with which I
have little experience, there are the even more daunting legal (FCC)
matters with which I am even less familiar. Obviously, no matter how
hard I study, there are limits to how much I can learn in a short time,
so any pre-processed input from someone who has experience is greatly
appreciated.

I *think* I may have found a way to get this project taken on by a
professional in this area. It's a tricky business. While Phil has hit
upon the "naivety' factor, he missed the "extremely limited resources"
part. Here's hoping.

In that case, all I would have to do is create a demo unit for
presentation that *does* what we need it to do. It wouldn't have to
have the range. It wouldn't have to operate at the frequencies that
the end product would. And would not have to have the security. It's
the difference between building something that 'works' and designing a
'product'. I feel well up to the former task. The latter scares the
hell out of me.

Anyway, I'm still very interested in coming up with the best solution I
can, if only to compare it to what actually gets designed assuming that
we can get this taken on.

To that end:

1. The target size is about 10x10x3 cm.

2. Battery life needs to be at least a few hours.

3. It needs to have a two channel remote control.

4. The first channel would power up a circuit that flashes a set of
LED's marquee style.

5. The second channel would operate a small buzzer motor.

6. Independently, monophonic voice quality audio would be transmitted
to the device. It would need to be loud
enough to be heard and understood by the wearer.

7. All devices would be performing these actions in unison.

8. The channel 1, channel 2 remotes, and the voice, may occur either
alone or in combination with each other.

9. All actions would be under manual control. But the operator would
be selecting combinations of actions from a menu in a browser based
application and executing them that way. He/she would not be pushing a
button on an appliance device like with a garage door opener. The
audio would be the output of a sound card in the server. It could be
reproducing either decoded mp3 or ogg files, or passing through real
time voice from the operator.

10. The transmission would be intermittent, not continuous.

11. It is understood that licensing for use of a higher power
transmitter and/or use of the particular frequencies used, may be
required.

12. I had been considering the possibility of using repeaters, but am
not sure what the legal requirements for that might be.


13. The thing about all of this that scares me the most is the security
issue. The fact that I need to operate all devices simultaneously, and
that the wearers would actually own the devices, taking them home with
them, plus the fact that these people are essentially anonymous, makes
it virtually impossible to secure this in such a way that someone could
not commandeer control of the devices for their own purposes, if even
in a limited area. This is particularly worrisome for the audio. The
"normal" methods of securing transmissions between pairs of
transmitters and receivers don't apply, here, so far as I can see.

In general, I would be interested in advice as to a general strategy to
pursue. There is obviously too much for me to learn in a short time.
So my current strategy is to find a direction that looks reasonable,
and focus my efforts on familiarizing myself with the specifics of
that. And, of course, seeing if I can get this project transfered to
people who know what they are doing. ;-)

Thanks again for your help,
Steve

 

[linnix]

...

6. Independently, monophonic voice quality audio would be transmitted
to the device. It would need to be loud enough to be heard

Not a problem.

and understood by the wearer.

I think this would be your biggest problem.
To transmit reasonable voice signal uncompressed would be tough.
Using compressed voice would bump up your cost
and power budget as well.

 

[Steve Bergman]

I think this would be your biggest problem.
To transmit reasonable voice signal uncompressed would be tough.
Using compressed voice would bump up your cost
and power budget as well.

Scaling this back, for the moment, and assuming that I am successful at
getting a qualified person or team to take on the real work, let me ask
about the demo/presentation unit that I would have to build to make
that happen.

This would have much less in the way of constraints. No range issues.
No security issues.

I am currently planning on using a small off the shelf 418MHz AM 2
channel remote control. And then add a small TDA7000 or TDA7010T based
receiver with an LM386 as the amp. Plus a simple marquee flashing
circuit for the LED's. The transmitter for the remote controls would
be controlled by a USB relay controller from the PC.

Would anyone have any recommendations for off the shelf boards that
might combine some of this functionality into a smaller space?

Thanks for any recommendations,
Steve

 

[linnix]

Scaling this back, for the moment, and assuming that I am successful at
getting a qualified person or team to take on the real work, let me ask
about the demo/presentation unit that I would have to build to make
that happen.

This would have much less in the way of constraints. No range issues.
No security issues.

I am currently planning on using a small off the shelf 418MHz AM 2
channel remote control. And then add a small TDA7000 or TDA7010T based
receiver with an LM386 as the amp. Plus a simple marquee flashing
circuit for the LED's. The transmitter for the remote controls would
be controlled by a USB relay controller from the PC.

Are you having one remote station, or more than one?
We planned on building something like that, and decided that they have
to
be transceivers. First of all, the master station has to determine
what remote
stations are in range. At the very least, determine if the remote
stations are
powered-up, before jamming the airway with data.

 

[Frank Raffaeli]

Thank you, Frank, for your helpful post. This all just landed on me
the other day, and in addition to the technical matters with which I
have little experience, there are the even more daunting legal (FCC)
matters with which I am even less familiar. Obviously, no matter how
hard I study, there are limits to how much I can learn in a short time,
so any pre-processed input from someone who has experience is greatly
appreciated.

I *think* I may have found a way to get this project taken on by a
professional in this area. It's a tricky business. While Phil has hit
upon the "naivety' factor, he missed the "extremely limited resources"
part. Here's hoping.

In that case, all I would have to do is create a demo unit for
presentation that *does* what we need it to do. It wouldn't have to
have the range. It wouldn't have to operate at the frequencies that
the end product would. And would not have to have the security. It's
the difference between building something that 'works' and designing a
'product'. I feel well up to the former task. The latter scares the
hell out of me.

Anyway, I'm still very interested in coming up with the best solution I
can, if only to compare it to what actually gets designed assuming that
we can get this taken on.

To that end:

1. The target size is about 10x10x3 cm.

2. Battery life needs to be at least a few hours.

3. It needs to have a two channel remote control.

4. The first channel would power up a circuit that flashes a set of
LED's marquee style.

5. The second channel would operate a small buzzer motor.

6. Independently, monophonic voice quality audio would be transmitted
to the device. It would need to be loud
enough to be heard and understood by the wearer.

7. All devices would be performing these actions in unison.

8. The channel 1, channel 2 remotes, and the voice, may occur either
alone or in combination with each other.

9. All actions would be under manual control. But the operator would
be selecting combinations of actions from a menu in a browser based
application and executing them that way. He/she would not be pushing a
button on an appliance device like with a garage door opener. The
audio would be the output of a sound card in the server. It could be
reproducing either decoded mp3 or ogg files, or passing through real
time voice from the operator.

10. The transmission would be intermittent, not continuous.

11. It is understood that licensing for use of a higher power
transmitter and/or use of the particular frequencies used, may be
required.

12. I had been considering the possibility of using repeaters, but am
not sure what the legal requirements for that might be.

13. The thing about all of this that scares me the most is the security
issue. The fact that I need to operate all devices simultaneously, and
that the wearers would actually own the devices, taking them home with
them, plus the fact that these people are essentially anonymous, makes
it virtually impossible to secure this in such a way that someone could
not commandeer control of the devices for their own purposes, if even
in a limited area. This is particularly worrisome for the audio. The
"normal" methods of securing transmissions between pairs of
transmitters and receivers don't apply, here, so far as I can see.

In general, I would be interested in advice as to a general strategy to
pursue. There is obviously too much for me to learn in a short time.
So my current strategy is to find a direction that looks reasonable,
and focus my efforts on familiarizing myself with the specifics of
that. And, of course, seeing if I can get this project transfered to
people who know what they are doing. ;-)

Thanks again for your help,
Steve

Thanks for the details on the application. I may be oversimplifying,
but this sounds like a restaurant pager - flashing lights and a small
moter, e.g.:
http://www.jtech.com/products/guest_alert.htm

Do you require two-way communication to the (10x10 cm) device, or is it
receive only?
Security: See "rolling code" algorithms, e.g.:
http://freepatentsonline.com/6956460.html
Other security methods may be superior. The most reliable ones need
2-way communication.

Is the voice arbitrary or can it be a pre-recorded message? This may
ease the agency aproval task.

What is the annual volume? Maybe you could interest someone in a
speculative R&D project.

Perhaps for your demo you could use one of the jtech units.

Frank Raffaeli
http://www.aomwireless.com/

 

[Phil Allison]

"Steve Bergman"

I *think* I may have found a way to get this project taken on by a
professional in this area. It's a tricky business. While Phil has hit
upon the "naivety' factor, he missed the "extremely limited resources"
part.

** That would obviously be because that phrase was NOT in your original
post.


BTW: YOU missed this:

" Wonder if a GIANT audio induction loop might just do what the OP actually
needs. "

Avoids RF completely and uses only simple audio electronics.




........ Phil

 

[Steve Bergman]

On Jan 20, 11:44 am, "Steve Bergman" <[email protected]> wrote:

Thanks for the details on the application. I may be oversimplifying,
but this sounds like a restaurant pager - flashing lights and a small
moter, e.g.:
http://www.jtech.com/products/guest_alert.htm

Do you require two-way communication to the (10x10 cm) device, or is it
receive only?
Security: See "rolling code" algorithms, e.g.:
http://freepatentsonline.com/6956460.html
Other security methods may be superior. The most reliable ones need
2-way communication.

Is the voice arbitrary or can it be a pre-recorded message? This may
ease the agency aproval task.

What is the annual volume? Maybe you could interest someone in a
speculative R&D project.

Perhaps for your demo you could use one of the jtech units.

We need one-way communication only.

Yes, I am familiar with the jtech units. They do pretty much
everything except the real time audio. The audio needs to be
transmitted from the server. I believe the jtechs do have an option to
play an internally stored audio message. But, unfortunately, we need a
larger repertiore of sound bites, selectable in real time from the base
station/server. Still, I should probably go back and reconsider just
what I might do with the Jtechs.

Would a rolling code algorithm be compatible with controlling a large
number of these acting in unison?

The volume could end up being in the tens of thousands. And yes, we're
planning to pitch to a third party who might take this on out of
self-interest.

Thanks,
Steve

 

[Steve Bergman]

** That would obviously be because that phrase was NOT in your original
post.

I figured that would be obvious from the fact that they put me on it.
;-)

BTW: YOU missed this:

" Wonder if a GIANT audio induction loop might just do what the OP actually
needs. "

Avoids RF completely and uses only simple audio electronics.

I didn't miss seeing it. I missed your *meaning*. I thought you were
talking about a big loop antenna for the rf.

If I understand you correctly, you are proposing that the loop carry an
audio frequency signal and that the receiver devices just amplify the
AF directly?

What would be the implications for someone who wanted to cut into the
broadcast? They wouldn't have a loop of their own, obviously.

I guess my receiver would just be an AF amplifier with some sort of
coil antenna?

I'm guessing that in doing it this way, I'm not really limited on
power. The loop could just have the appropriate impedance and be fed
by a power amp at whatever power level is necessary.

Thanks,
Steve

 

[Phil Allison]

"Steve Bergman"

I didn't miss seeing it. I missed your *meaning*. I thought you were
talking about a big loop antenna for the rf.

** Funny how it says " audio induction loop " isn't it then ??

If I understand you correctly, you are proposing that the loop carry an
audio frequency signal and that the receiver devices just amplify the
AF directly?

What would be the implications for someone who wanted to cut into the
broadcast? They wouldn't have a loop of their own, obviously.

I guess my receiver would just be an AF amplifier with some sort of
coil antenna?

I'm guessing that in doing it this way, I'm not really limited on
power. The loop could just have the appropriate impedance and be fed
by a power amp at whatever power level is necessary.

** Google " audio induction loop " .

Come back when you are better informed.



........ Phil

 

[Eeyore]

And then add a small TDA7000 or TDA7010T based
receiver with an LM386 as the amp.

Why does every damn person consider that LM386 POS ?

It was crap when it was released.

Graham

 

[Frank Raffaeli]

Yes, I am familiar with the jtech units. They do pretty much
everything except the real time audio. The audio needs to be
transmitted from the server. I believe the jtechs do have an option to
play an internally stored audio message. But, unfortunately, we need a
larger repertiore of sound bites, selectable in real time from the base
station/server. Still, I should probably go back and reconsider just
what I might do with the Jtechs.

Would a rolling code algorithm be compatible with controlling a large
number of these acting in unison?

The volume could end up being in the tens of thousands. And yes, we're
planning to pitch to a third party who might take this on out of
self-interest.

Thanks,
Steve

Thanks for the additional info. If the audio repertoire could be stored
in a data-flash, then you may be able to license this device under the
remote-control restrictions. MP3 playback chips are cheap if you
require compressed storage. There would be several advantages to using
the remote-control model that may improve range and reliability, as
well as time-to-market.

Yes, rolling codes can be used with many receivers and one master. Each
receiver must be addressed separately. I'm assuming the address and
command is part of the encoded signal from the master. The tricky part
is keeping sychronization.

Frank

 

[Frithiof Andreas Jensen]

I'm a programmer, not an expert in matters RF. But due to factors
beyond my control, I have been called upon to make some decisions about
the design of a device because "I'm a technical guy". ;-)

Learn from the Boss dumping on you and: DELEGATE!!
I.E Just go Buy It - doing this job yourself is a certain loser.

..... Perhaps something based on the guts of those el-cheapo walkie-talkies would
work (the ones retailing at USD 40 a pair, a couple of km range and a keypad for
"sekrety"). Someone will already have done that.

 

[Frithiof Andreas Jensen]

While Phil has hit
upon the "naivety' factor, he missed the "extremely limited resources"
part. Here's hoping.

How come "ressources" is suddently your problem??

If "the man" wants a job done, "the man" can effing well pay whatever it really
costs - or - decide that it is not worth doing at all. It is really that easy.
Your responsibility is to give some realistic numbers for that deciesion; the
easiest way to do that is to ask for some tenders - You *cannot, ever* build a
deployable one-off design any cheaper than the stuff you can buy.

In that case, all I would have to do is create a demo unit for
presentation that *does* what we need it to do. It wouldn't have to
have the range. It wouldn't have to operate at the frequencies that
the end product would. And would not have to have the security. It's
the difference between building something that 'works' and designing a
'product'. I feel well up to the former task. The latter scares the
hell out of me.

Hack a walkie, apply some cardboard, hotmelt glue, spraypaint and whatnot!

In My Experience what people like to see in demo's is "What this
product/technology can do for me?" and "WHY do we want this?" NOT the "How is it
done?". If one points out that one is cheating, then I.M.E. it is totally
accepted as long as one has an idea of the technical issues in order of risk
(riskiest goes first).

In general, I would be interested in advice as to a general strategy to
pursue. There is obviously too much for me to learn in a short time.

Your strategy is to stay well away from tasks that you cannot perform with
confidence!

All that really counts are the results - if you "cheat", go buy the stuff and it
works, what people will remember is: The Result, that the task was handled and
done successfully!

The exact same principle applies if you spend 1,5 years hacking some barely
working stuff up: people will remember that recall of the crummy product made by
that idiot designer (now looking for new challenges) for a long time! Therefore,
you cheat!!

 

[Charlie Edmondson]

linnix wrote:




Scaling this back, for the moment, and assuming that I am successful at
getting a qualified person or team to take on the real work, let me ask
about the demo/presentation unit that I would have to build to make
that happen.

This would have much less in the way of constraints. No range issues.
No security issues.

I am currently planning on using a small off the shelf 418MHz AM 2
channel remote control. And then add a small TDA7000 or TDA7010T based
receiver with an LM386 as the amp. Plus a simple marquee flashing
circuit for the LED's. The transmitter for the remote controls would
be controlled by a USB relay controller from the PC.

Would anyone have any recommendations for off the shelf boards that
might combine some of this functionality into a smaller space?

Thanks for any recommendations,
Steve

First off, I would suggest looking at Zigbee and the various micros out
there to support it. It would provide the power levels you need, the
long battery life, and the ability to send encoded audio. It would also
provide the security that you want. Even simpler would be to use an IR
LED broadcast system, with the caveat that you need a lot more base
stations...

Charlie