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Bluetooth transciever in metal box - how to expose antenna?

P

P E Schoen

Jan 1, 1970
0
I am considering adding Bluetooth to a piece of test equipment I am
designing. I am not really very familiar with it, but it seems to be pretty
easy to implement by connecting a transciever module to the microcontroller
RX/TX lines and having the PC find it and then using it as a wireless serial
port. I just purchased a little Bluetooth 4.0 USB dongle for the PC (only
$12) and I ordered a module for the PIC controller of the test set:
http://www.ebay.com/itm/181072994083
Specs:
http://cxem.net/arduino/download/HC Serial Bluetooth Products 201104.pdf

I'm fairly sure it will not work encased in an aluminum box with a 1/8"
aluminum panel, although possibly the signal could get in and out through
some openings that are locked only by an LCD display and other components. I
will probably need to expose the antenna, or add one that might even be
incorporated into the panel overlay which has a membrane keypad. We may need
to redesign the panel and perhaps an antenna could be added, but otherwise
(and for the prototype), perhaps I can just cut a rectangular slot for the
antenna portion of the PCB to be exposed, and maybe add a plastic cover to
protect it.

Has anyone had any experience with these modules, or others, and
specifically using them in a metal enclosure?

And is it possible to use the WiFi controller built into the PC (Toshiba
Satellite C655) for Bluetooth?

I did not find any Bluetooth adapters in Device Mangler and when I plugged
in the USB adapter it enumerated and installed automagically. But I don't
have any Bluetooth devices to test it with.

It installed as follows:

(Bluetooth Radios)
Broadcom BCM20702 Bluetooth 4.0 USB Device
Microsoft Bluetooth Enumerator

(Network Adapters)
Bluetooth Device (Personal Area Network)
Bluetooth Device (RFCOMM Protocol TDI)

I don't see it listed as a COM port, but maybe it first needs to be paired
with a slave device.

Thanks,

Paul
 
N

Nico Coesel

Jan 1, 1970
0
P E Schoen said:
I am considering adding Bluetooth to a piece of test equipment I am=20
designing. I am not really very familiar with it, but it seems to be =
pretty=20
easy to implement by connecting a transciever module to the =
microcontroller=20
RX/TX lines and having the PC find it and then using it as a wireless =
serial=20
port. I just purchased a little Bluetooth 4.0 USB dongle for the PC =
(only=20
$12) and I ordered a module for the PIC controller of the test set:
http://www.ebay.com/itm/181072994083
Specs:
http://cxem.net/arduino/download/HC Serial Bluetooth Products 201=
104.pdf

I'm fairly sure it will not work encased in an aluminum box with a 1/8"=20
aluminum panel, although possibly the signal could get in and out =
through=20
some openings that are locked only by an LCD display and other =
components. I=20
will probably need to expose the antenna, or add one that might even be=20
incorporated into the panel overlay which has a membrane keypad. We may =
need=20
to redesign the panel and perhaps an antenna could be added, but =
otherwise=20
(and for the prototype), perhaps I can just cut a rectangular slot for =
the=20
antenna portion of the PCB to be exposed, and maybe add a plastic cover =
to=20
protect it.

Has anyone had any experience with these modules, or others, and=20
specifically using them in a metal enclosure?

A metal enclosure is a no-go. Otherwise most modules are complete crap
anyway. My experience with using Bluetooth is that you need to write a
lot of software around it to mitigate problems with lost pairings or
connections which won't disengage.
And is it possible to use the WiFi controller built into the PC (Toshiba =

Satellite C655) for Bluetooth?

No. Bluetooth is not Wifi
 
I am considering adding Bluetooth to a piece of test equipment I am

designing. I am not really very familiar with it, but it seems to be pretty

easy to implement by connecting a transciever module to the microcontroller

RX/TX lines and having the PC find it and then using it as a wireless serial

port. I just purchased a little Bluetooth 4.0 USB dongle for the PC (only

$12) and I ordered a module for the PIC controller of the test set:

http://www.ebay.com/itm/181072994083

Specs:

http://cxem.net/arduino/download/HC Serial Bluetooth Products 201104.pdf



I'm fairly sure it will not work encased in an aluminum box with a 1/8"

aluminum panel, although possibly the signal could get in and out through

some openings that are locked only by an LCD display and other components. I

will probably need to expose the antenna, or add one that might even be

incorporated into the panel overlay which has a membrane keypad. We may need

to redesign the panel and perhaps an antenna could be added, but otherwise

(and for the prototype), perhaps I can just cut a rectangular slot for the

antenna portion of the PCB to be exposed, and maybe add a plastic cover to

protect it.



Has anyone had any experience with these modules, or others, and

specifically using them in a metal enclosure?



And is it possible to use the WiFi controller built into the PC (Toshiba

Satellite C655) for Bluetooth?



I did not find any Bluetooth adapters in Device Mangler and when I plugged

in the USB adapter it enumerated and installed automagically. But I don't

have any Bluetooth devices to test it with.



It installed as follows:



(Bluetooth Radios)

Broadcom BCM20702 Bluetooth 4.0 USB Device

Microsoft Bluetooth Enumerator



(Network Adapters)

Bluetooth Device (Personal Area Network)

Bluetooth Device (RFCOMM Protocol TDI)



I don't see it listed as a COM port, but maybe it first needs to be paired

with a slave device.



Thanks,



Paul

Maybe Chapter 4> http://218.2.28.130/tushu/book/book46/2009875549013.pdf
 
P

P E Schoen

Jan 1, 1970
0
"Dave Platt" wrote in message
It would probably not work at all well, if it works at all.
Take a look at

for some ideas. You might be able to incorporate a "printed
inverted F" antenna into one of the panels or overlays.

Good information. It seems that possibly a vertical antenna may be best,
something like the following which is similar to that on some walkie-talkies
and routers:
<http://www.mouser.com/ProductDetail/Roving-Networks/RN-SMA-4/?qs=sGAEpiMZZMtqO%2bWUGLBzeAlOUaKrl2Gg>

It's a little expensive at $7 but this is for a $3000 test set and the
Bluetooth option could easily be a $200 adder. Maybe a female SMA connector
can be mounted on the panel and connect to the module with a 50 ohm coax
cable:
<http://www.mouser.com/ProductDetail...iMZZMuLQf%2bEuFsOrnl3T6JYQ6%2bUOJgMTAkJ4%2bo=>
<http://www.mouser.com/pdfdocs/TEConnectivity_KOAXXA_SMA_QRG_0112.pdf>

I might need to get a module that has an SMA connector for proper matching.
<http://www.mouser.com/ProductDetail...E-I-RM/?qs=sGAEpiMZZMtqO%2bWUGLBzeHWBrVBExf6F>
<http://www.mouser.com/ds/2/349/Bluetooth-RN-24-DS-3184.pdf>

These modules are $53 each but are probably far superior to the cheap
Chinese versions at about $10.

Thanks for the ideas. I'll see how the module works when I get it in a few
days.

Paul
 
P

P E Schoen

Jan 1, 1970
0
"Jeff Liebermann" wrote in message
Which one?

It's an IOGear Model GBU521
You'll have to cut the trace to the wiggly gold plated antenna, and
solder the very tiny coax that usually comes with Wi-Fi antennas.
<http://802.11junk.com/jeffl/antennas/coaxial/slides/coax-ant.html>
Or, you could just drill a hole, install a panel mount RP-SMA
receptacle, and screw in a variety of available wi-fi antennas.

That seems to be the best option for now.
I've had a little in the distant past. The client failed FCC Part 15
incidental radiation and decided to metalize the inside of the plastic
enclosure. Then, they were wondering why the BlueGoof range was
seriously lacking. I had to scrape off enough metalization to get a
2.4Ghz signal through, but not so big a hole that it would again fail
part 15. It was not fun.

I suppose we should look into certification. Some of our test sets are used
in nuclear power plants and government installations where RFI may be a
problem.
If you have a smartphone, the BT section should be suitable for
testing your laptop dongle. Just make sure you set the smartphone
to be "visible" for pairing.

I have an Archos 70 Internet Tablet which I powered up and it was found by
the PC and paired, although the Archos device indicated it was not
connected. I was not able to assign a COM port but I was able to send a file
from the PC to the device via Bluetooth. The devices were only inches apart
so it was not a good test of distance. But at least I know the dongle works.
The Bluetooth module may offer itself as a COM port.
You'll see a BT icon in the system tray on your laptop. Right
click and select something like "settings". There should be
a tab for selecting a COM port.

That did not seem to work, but I was able to connect and send a file.

Thanks,

Paul
 
J

John Walliker

Jan 1, 1970
0
You might consider creating a slot antenna in the housing. This would
be
a fairly narrow slot aboiut 1/2 wavelength long and driven half way
along
on each side (from the inside). You might need a balun for best
results,
but even without one it could work well. (You need some free space
inside the slot as well as outside - or even better a reflecting plate
spaced
appropriately behind it.)

Another possibility is creating half-wave slots in the housing to let
the
signal out from an internal antenna. They would act as filters
letting
the BT signal (and harmonics) in and out. Ensure the polarisation
of the slots matches the internal antenna if possible. The slot
polarisation
is at right angles to that of a wire antenna.

Whatever antenna you use, try to keep it as far away from other
conductive materials as you can. An antenna is not just the wire or
slot. It also includes the space immediately around it. If that
space is
occupied, the antenna will lose efficiency or bandwidth. If it is a
ready-
made antenna it will be detuned.

Its hard to beat a quarter-wave monopole with a good ground plane and
plenty of space around it. Anything which tries to be smaller
inevitably
results in compromises on efficiency or bandwidth.
Narrow bandwidth means more risk that production variations or
environmental influences will detune the antenna giving a dramatic
fall
in output.

John
 
U

Uwe Hercksen

Jan 1, 1970
0
P said:
I have an Archos 70 Internet Tablet which I powered up and it was found
by the PC and paired, although the Archos device indicated it was not
connected. I was not able to assign a COM port but I was able to send a
file from the PC to the device via Bluetooth. The devices were only
inches apart so it was not a good test of distance. But at least I know
the dongle works. The Bluetooth module may offer itself as a COM port.

Hello,

I tried to connect a PC to a cell phone via Bluetooth, it did not work,
even over a very short distance of some inches. I had to switch of a
DECT wireless portable phone, than I could connect via Bluetooth.
Bluetooth uses very low transmitter power, but DECT uses much more power
and a frequency close to Bluetooth.

Bye
 
B

Boris Mohar

Jan 1, 1970
0
I am considering adding Bluetooth to a piece of test equipment I am
designing. I am not really very familiar with it, but it seems to be pretty
easy to implement by connecting a transciever module to the microcontroller

Slot antenna?


Regards,

Boris Mohar

Got Knock? - see:
Viatrack Printed Circuit Designs (among other things) http://www.viatrack.ca

void _-void-_ in the obvious place
 
W

whit3rd

Jan 1, 1970
0
I am considering adding Bluetooth to a piece of test equipment I am
designing. I am not really very familiar with it, but it seems to be pretty
easy to implement by connecting a transciever module to the microcontroller
RX/TX lines and having the PC find it and then using it as a wireless serial
port. I just purchased a little Bluetooth 4.0 USB dongle for the PC (only
$12)

Well, if you can put a USB socket somewhere on your test equipment,
there's a $12 solution for you.

I've seen some bluetooth for PCs done as a USB cable, to a molded
plastic blob that attaches outside the case, under a piece of plastic
trim, with its cable snake-ing through a perforation and plugging into
one of the USB headers.
 
P

P E Schoen

Jan 1, 1970
0
"whit3rd" wrote in message
Well, if you can put a USB socket somewhere on your test equipment,
there's a $12 solution for you.
I've seen some bluetooth for PCs done as a USB cable, to a molded
plastic blob that attaches outside the case, under a piece of plastic
trim, with its cable snake-ing through a perforation and plugging into
one of the USB headers.

The USB bluetooth for PCs is not the same as that for a slave device. I have
USB implemented on the instrument PCB but it is not configured as a host. It
may be possible to use USB OTG to do that, but I think it will involve a lot
more than just connecting a module to the RX/TX lines of the processor.
There are modules with an antenna and a cable for under $20 that should take
care of the issues.
http://www.ebay.com/itm/271109056178

Thanks,

Paul
 
P

P E Schoen

Jan 1, 1970
0
Just as an update, I received the Bluetooth module
http://www.ebay.com/itm/181072994083 in the mail on Saturday and I was able
to connect it to a PIC project which reads four ADC channels and transmits
the values every 5 seconds at 9600,N,8,1, which happens to be the default
for the module. I had already installed the Bluetooth USB dongle on my
laptop and paired it with my Archos 70 tablet and was able to send a file.
It did not appear to have a COM port as a service.

The module on the datalogger was discovered and drivers were automagically
installed and it showed that COM14 was available. I chose that in my TTYdemo
application and it worked a charm. I was unable to block the transmission by
cupping my hand around the module, and even a 7"x9" 12 gauge steel plate did
not interrupt the data stream. So I think it may be enough to expose just
the 1/4" x 1/2" x 1/16" PCB antenna through a slot in the panel, perhaps
protected by a small plastic piece.

I'm happily amazed at the simplicity and low cost (under $20) of
implementing this technology. It may be a big selling point to be able to
control and read data from the test set using a laptop computer or even a
tablet device or smart phone. Maybe even make a detachable keypad with
Bluetooth on both ends. This may be much more practical than my previous
idea of implementing an Ethernet and WiFi connection where the test set
would appear as a web page with an HTML keypad. It's cool to be able to
control the device and read data from anywhere in the world over the
internet, but it's really not necessary and may present security and safety
issues.

But now I need to figure out how to program the equivalent of a keypad and
display on the tablet device. The Archos 70 is an Android device and I
didn't have any luck making an App with the DTK and Windows emulator. Maybe
it will be easier to get a Win7 tablet where the same App will work on a
laptop or hand held device, and I won't need to learn a new OS.

Thanks,

Paul
 
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