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Old 10th September 2002, 03:57 PM   #11
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Lightbulb What are your power requirements?

Thus far, transmission of the audio has been discussed. What are you going to power your receiver/demodulator units and speakers with? You mention that the cabling is an issue. Are power cables also an issue?

If so, better factor in a power source.

Years ago, had a student ask me about an interesting idea, a wireless communications link for motorcycle helmet headsets. Many larger touring motorcycles use stereo headsets, plus a microphone for communication between the rider and passenger, as well as CB radio between bikes.

There were several problems:

The idea was to employ infrared transmission. In daylight hours, the sun provides enough IR noise to blank out most any signal. The signals required were L + R audio, and a Mike signal.

I normally mounted the helmet speakers away from the ear, like a Stax headset. The speakers were cut into the foam shell of the helmet, at least 50mm off-axis (above) the ear, and 30mm away, allowing the rider to hear as much ambient sound as possible. Many riders wanted closer installation, but I never agreed to mount the drivers any closer! In this configuration, "cranking up" the system would require higher power, and the perceived sound was like speakers "floating" a foot or so away from the ear.

With this in mind, the problem was providing adequate power for the system. Granted, one could have cheated by using efficient "ear bud" Walkman type speakers, but that would be both illegal and unsafe.
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Old 10th December 2002, 09:49 PM   #12
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Default Bluetooth wireless

I too have been investigating the possibilities of using bluetooth to transport digital audio. How is this coming along for you? are you sending SP/DIF signals or something else? is latency an issue? My idea is to send digital audio signal to the speaker that has an internal class D amp fo reffiecency to run on battery power, what are your ideas?
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Old 10th December 2002, 10:44 PM   #13
Rarkov is offline Rarkov  England
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Hi,
My problem with cabling is the long speaker cable stretches. Latency is an issue but I would think it'd be negligable for bluetooth. As long as my speakers are all relativly in phase I'm OK with that.

I suspect that not sitting dead central or leaning over to pick something up off the floor, or a speaker slightly out of line would cause more problems than latency...

I have found Bluetooth to be very cheap. I found 5 chips (BGA package ) for 45 or $75US...It is a cheap method!

Gaz
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Old 11th December 2002, 12:50 AM   #14
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a point not yet brought up...

volume control It always seemed to me to that the best way to transmit the signal is in spdif or something akin to it. That part while technically challenging seems fairly straight forward. The problem I ran into while thinking about this was the volume control. If you use spdif or its equivelents you would get HiFi for the price of a few a/d, d/a, and a transmission system. But if you do this how to you get the volume signal out? Perhaps there is a really simple digital attenuator, but it seemed to me that this was throwing away a fair amount of data. I came up with two or three systems, the perhaps easiest was to get a few frequency hopping portable phones and rework them a bit. The second would be to transmit spdif digitally and then use an FM signal to transmit the gain(volume). The third and best solution would be to re-encode the spdif to include volume information. But this requires programming a computer for each transmitter and reciever.

Hopefully this is all moot because of a good way to do digital attenuation, but I haven't seen one (because I haven't yet looked for one seriously)
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Old 11th December 2002, 12:58 AM   #15
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Quote:
Originally posted by Rarkov
I have found Bluetooth to be very cheap. I found 5 chips (BGA package ) for 45 or $75US...It is a cheap method!
What chips are you using? My roommate is trying to find a way to implement bluetooth, and that is a great price. How are you going to get around the BGA package?

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Old 17th December 2002, 04:02 AM   #16
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rarkov, upon reading the bluetooth standard manual, it appears to be a packetized standard. How could you send a stream of data along in packets without a buffer or computer at the other end. I assume that there will be no bufffer in the speaker itself because it would cause time delay issues if a packet didnt get through. we need a wireless interface that does not use packets. can you "hack" up one of those bluetooth modules to send raw data and recieve raw data? any more details about your project are welcome!
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Old 17th December 2002, 07:59 AM   #17
Rarkov is offline Rarkov  England
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Hi,
Well, this sounds like it's getting well beyond my abilities. There is an alternative...433MHz AM License exempt channels. I'm sure if we could find a module with a high enough baud, we coud send SPDIF or PWM etc...

Might be easier...
Gaz
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Old 17th December 2002, 01:26 PM   #18
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Quote:
Originally posted by Yoda
rarkov, upon reading the bluetooth standard manual, it appears to be a packetized standard. How could you send a stream of data along in packets without a buffer or computer at the other end. I assume that there will be no bufffer in the speaker itself because it would cause time delay issues if a packet didnt get through. we need a wireless interface that does not use packets. can you "hack" up one of those bluetooth modules to send raw data and recieve raw data? any more details about your project are welcome!
The stream of data may use packets, but from what I remember, a proprietary Bluetooth receiver will, with the help of some external logic, depending on the Bluetooth component used, turn this back to data usable by a DAC.
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Old 17th December 2002, 03:21 PM   #19
Rarkov is offline Rarkov  England
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That's interesting...
Bluetooth chips aren't all that complicated...It was meant and designed to be a one-chip-does-it-all solution to wireless networking peripherals...As a result of it being developed by many companies, info is easy enough to come by...

The problem is with the miniturisation of bluetooth components. It is mainly for mobile phones and other handheld devices...We are not interested in that and it is far more important to be solderable...Well, for me at least...

Any one seen BT chips in DIP packages?!

Gaz
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Old 18th December 2002, 01:49 PM   #20
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Default Any one seen BT chips in DIP packages?!

That ain't gunna happen.
Best you get with the times and learn smd soldering techniques.

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