DIY Bluetooth mod for range increase

DIY Bluetooth mod for range increase

Postby brewski » Tue Jun 17, 2014 4:44 am

I ordered one of these $10 Multiwii Bluetooth modules http://www.ebay.com.au/itm/281318498832 ... 1439.l2649
& found it works well with EZ-GUI running on my Galaxy 3. The only issues were -
1. It locked up Crius AIO P V2 if connected at power up. After failing to find a resolution on Forums I installed a miniature switch (you can see in photo) in +5 v line to module.
2. Range was only about 15m outside. I solved this by cutting away a section of about 5mm of copper onboard antenna, leaving about 2mm at start of antenna.
I then soldered 30mm of flexible insulated cable to the 2mm section. A blob of holt melt glue ensured that connection would be secure. See attached photo
The length of wire is critical as 32mm is 1/4 wavelength at 2.4Ghz which is the frequency of Bluetooth. Wire is 30mm + 2mm of original antenna is spot on.
I now get >200metres at ground level outside & further when quad is flying.
This is all totally legal as all we have done is use a proper 1/4 wave antenna instead of the crappy one that designer could fit on PCB.
Attachments
DSC_0489.JPG
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Re: DIY Bluetooth mod for range increase

Postby copterrichie » Tue Jun 17, 2014 4:50 am

That bluetooth modification works very well, even better if you can do both sides. I have a USB Bluetooth adapter I modified in conjunction to the bluetooth on the copter.

Nice Job.
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Re: DIY Bluetooth mod for range increase

Postby brewski » Tue Jun 17, 2014 5:21 am

Yes the phone Bluetooth is the limiting factor. Although I can read data from quad at 200m I would not be game to write settings using phone at this range.
Different phones will also give different results depending on Bluetooth version, antenna etc.
A bit hard to mod antenna on phone unfortunately. A modded USB Bluetooth plugged into OTG on phone might work.

Being an electronics engineer I love to reverse engineer stuff I buy so downloaded data sheets on the Bluetooth RF module IC & 8mb RAM IC used on the modules.
Both the RF IC & RAM IC operate on 3.3 V & these is a 3.3V regulator on these Bluetooth modules. What is a bit of a worry is that the data lines from Crius AIOP V1 & V2 plus any clone boards are at 5v level & no level shifting has been installed.
According to data sheet the module TXD is 5V tolerant but RXD input requires 3v so level shifting is required or IC can be damaged.
This is easily done by cutting RXD track under board & installing 1K resistor to RXD on rear of socket to RXD on module. Install 3.3K resistor from + 3.3V to RXD socket rear. Next install small shottsky diode (polarity as shown in diagram) in cable from serial port 0 on FC.
RXD data levels re now 3V.
Attachments
Bluetooth level shift 5 to 3 v.png
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Re: DIY Bluetooth mod for range increase

Postby brewski » Sat Jun 21, 2014 10:55 am

Yeah they do this in cinemas & live theatre some places in Australia. I agree too as nothing worse than a bloody cellphone ringing in the middle of a performance.
Where we are using quad with phone running EZ-GUI there is no chance of jamming as this is very short range by design & regulation.
The problem with the Chinese Bluetooth modules & I suspect even the originals is that Bluetooth range is severely limited by the aerials on PCB. Disconnect by cutting away track & attaching a vertical 1/4 wave antenna & range is >200m with a modern smartphone or tablet.
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Re: DIY Bluetooth mod for range increase

Postby BuBu » Mon Sep 15, 2014 9:55 pm

Hi, thanks a lot for your tip with the range mode! There is maybe a market for selling some mid-range Bluetooth dongles ;-)

By the way, have you tried with a half or full wave length antenna?
Also, I think that when one shortens the antenna size, he should compensate with a self so the antenna behaves the same way. So if you extended the antenna, maybe there would be a self to remove or reduce?
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Re: DIY Bluetooth mod for range increase

Postby brewski » Tue Sep 16, 2014 12:09 am

BuBu wrote:Hi, thanks a lot for your tip with the range mode! There is maybe a market for selling some mid-range Bluetooth dongles ;-)

By the way, have you tried with a half or full wave length antenna?
Also, I think that when one shortens the antenna size, he should compensate with a self so the antenna behaves the same way. So if you extended the antenna, maybe there would be a self to remove or reduce?


No I haven't tried half or full length antenna but doubt there would be much increase in range. As I mentioned the phone BT transceiver is the main limiting factor & it is not possible to add better antenna to most phones. An external BT module plugged into phone would work, but a set of 3DR radios would be a far better option.
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Re: DIY Bluetooth mod for range increase

Postby Hoppsan_84 » Thu Sep 18, 2014 9:40 am

How much influence does the length of the antenna?
If for example, I have 31 mm?

I have done the mod but have far from 200 meters range, maybe 50 max.
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Re: DIY Bluetooth mod for range increase

Postby brewski » Thu Sep 18, 2014 11:50 am

Hoppsan_84 wrote:How much influence does the length of the antenna?
If for example, I have 31 mm?

I have done the mod but have far from 200 meters range, maybe 50 max.


Considering 10m is considered max for BT you are doing pretty good!
But you can get better as you have found. If you cut track on module antenna just where it starts the zig zag, you should have 2mm of copper to solder to. Cut insulated flex wire to 30mm & you should be pretty close to 1/4wave @ 2.4GHZ. Cut off 1mm more if no improvement & test range. Then add a drop of holtmelt glue or epoxy to secure join.
I get approx. 200m+ with my Samsung GalaxyS3 in open park. Not all smartphones are as good with BT. My old Galaxy S only good for about 100m.
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Re: DIY Bluetooth mod for range increase

Postby Hamburger » Fri Sep 19, 2014 10:55 am

I get about 50 to 100m with copter in air line of sight unmodded.
Just using original pcb antenna of 6$ modules.

If with antenna you get 50m then antenna is wrong.or your board is inferior
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Re: DIY Bluetooth mod for range increase

Postby wiwitop » Wed Oct 15, 2014 12:38 pm

Multiwii EZ-GUI accepts serial connection. I connected a 433MHz radio module on the usb port of my Galaxy Note 3. I was happy to see it's working perfectly.
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Re: DIY Bluetooth mod for range increase

Postby Su-33 » Tue Oct 21, 2014 12:30 pm

brewski, have you tried the EGBT046s with the naze 32? i don't get answers in the naze 32 thread..
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Re: DIY Bluetooth mod for range increase

Postby brewski » Tue Oct 21, 2014 8:37 pm

Su-33 wrote:brewski, have you tried the EGBT046s with the naze 32? i don't get answers in the naze 32 thread..

No, but can't see why it wouldn't work provided you have a spare serial port. Even with a spare serial port as I have on my Crius AIOP V2 I have to switch the +5V off during boot or FC will not initialise.
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