Messages

391

General Discussion / Re: USB Power warning

« on: May 17, 2016, 02:31:45 pm »

A common problem. Wire the gubbins up in a tiny metal box (Maplin etc.) and earth the case sorts it out and a lot cheaper that the certified stuff

That can help with the radiated emissions, at the expense of potential overheating of the cheap chargers, they often run quite hot when anywhere near their rated capacity.  Some try and use the cigarette socket as a shield and a heat sink, which isn't much use.  The majority of them have horrendous conducted emissions too (that turn your wiring into an antenna for the interference, both supply and USB sides) as you don't have to test for that on battery powered chargers they just ignore it for the likes of CE compliance. 

Anything designed for use in aviation has very strict radiated and conducted emissions requirements, for obvious reasons.

392

General Discussion / Re: PAW in Australia?

« on: May 17, 2016, 08:15:04 am »

Having discovered that FLARM in Australia uses 921 MHz, can somebody tell me what frequency FLARM uses in the UK? Just trying to widen my knowledge of such things.

Thanks
Bill

FLARM uses various bands depending on what region it is set to.

frequency bands: Europe/Africa SRD-F 868.0 - 868.6 MHz (frequency hopping), NZ 869.25 MHz, Australia 915 – 928 MHz (frequency hopping), USA 905 – 925 MHz (frequency hopping); less than 1 % Duty Cycle

In the UK it uses 868.2 I believe.  Their latest FW update also tweaks the frequency so to harmonise the frequency used for North/South america

FLARM is based on the Nordic Semi nRF905 chipset, the Si chipset used in the Bridge can also operate in FHSS mode if required.  Whilst they state frequency hopping, given you can quite easily pickup and decode the raw FLARM packets with a simple SDR I doubt there is much in the way of true pseudo random hopping going on.  I don't recall that FHSS was mandated within the ISM band, in any region.

It shouldn't be too difficult to produce a suitable Bridge for AUS/USA/NZ, especially if it doesn't need to communicate with the EU version.  There are a number of worldwide certified COTS RF Modules readily available that would do the job.

393

General Discussion / Re: Results and setups

« on: May 13, 2016, 06:33:21 pm »

Doesn't the pinout mean that a standard 3.5mm stereo jack will work, albeit that it shorts the video to ground when doing so?

Should be fine, I assume Lee outputs both L&R channels, in which case a mono plug could be used as most intercoms etc. are mono?

394

General Discussion / Re: Results and setups

« on: May 12, 2016, 10:11:41 pm »

Raspberry Pi uses a commonly available 3.5mm 4-pole 'TRRS' Jack socket. Plug needs to be wired:-

Tip         =  Left Audio Channel
1st Ring  =  Right Audio Channel
2nd Ring =  Ground
Sleeve.    =  Video output (not used)

Be careful, most commercial cables aren't wired that way!

What I did was bought a long commercial lead, cut it in half and worked out the wiring colours by continuity testing. I then made one half up into a mono audio lead to connect via a single phono plug to my Flycom box and it works great.

How you connect the 'open' end will depend on your own intercom/headset system, so I can't help you there I'm afraid.

Regards

Peter

A picture may help some people...
edit: apologies if this image is huge, if a mod wants to shrink it feel free.

395

General Discussion / Re: Results and setups

« on: May 12, 2016, 08:27:23 pm »

The specific band is SRD/ISM 869.40 - 869.65 Mhz

Be interesting to know how interferance is mitigated from other users of this single slot.

i.e
Fire alarm systems
Wireless audio Individual item tagging Intruder alarm systems
Assistive listening
devices
Asset tracking Home/Office automation
Access control
Remote controllers
Medical
Social alarms/Telecare
Smart meters
Telemetry
Automotive


This is a good one;-
https://stellarsupport.deere.com/site_media/pdf/en/guides/RTK/PFP15164_RTK_Network_869_MHz_EN.pdf
etc


and they use them as repeaters !

John

The chipset such radio modules are based on implement a packet based protocol, so anything transmitted is ignored if it isn't in the right format, there are also checksums, group IDs etc. within the RF packet engine. One reason for anyone using these kinds of things NOT to use the default group ID at the RF packet level, so the module ignores anything not 'addressed' to the group.  Then Lee's P3I protocol also has a checksum, such that if an RF packet gets through there is an additional checksum to be passed too before the data is used.
These frequencies also have a low duty cycle, for example sending a single data packet once every few seconds. These aren't continuous broadcast systems.

Fundamentally it is mostly handled within the RF chipset, from memory of e-mail exchanges the bridge is based on the Silicon Labs Si4432 chipset.

396

General Discussion / Re: Transceiver Interference

« on: March 08, 2016, 11:36:12 pm »

Lee  - it’s a white noise effect, and  it was a USAMS twin port charger, one of these:

http://www.ebay.co.uk/itm/NEW-TWIN-USB-USAMS-DUAL-2-PORT-3-1-AMPS-UNIVERSAL-CIGARETTE-SOCKET-CAR-CHARGER-/121911798279?hash=item1c62826a07:g:NFIAAOSwYlJW1uxJ

We have only connected the PAW to this one which I bought because of the higher current requirement.
I will try sorting out a battery supply to check that out too. We also have 2 12v sockets in the aeroplane, and have another (different) usb charger in the other one which drives an Aware gps. What I should have done is to switch the chargers, and see if the USAMS one causes the same interference when connected to the Aware. I will check this out the next time I fly!

Do you have a recommendation for a good USB charging socket?

Thanks
Rick

http://www.ebay.co.uk/itm/Adjustable-DC-DC-Boost-Step-up-Power-Converter-Module-XL6009-Replace-LM2577-/272041588474?hash=item3f56f136fa:g:68gAAOSwiwVWRUaf

These work pretty well, but you have to wire them in (don't forget a fuse).. adding extra capacitor also helps keep the noise down.  You need to use a multimeter to set the output voltage to 5V (or just a little higher, say 5.25V), then it's best to glue up the potentiometer with cyano so it doesn't readjust itself with any vibrations.


Cheaper than a £100+ power supply.

I bought something like those to look at, before they rebranded their knock off LM2577 as something else to get round selling fake chips. Would I trust one of these in the air, no, there is a reason they are 99p and no doubt someone will find out soon enough.

I think I bought 5 for £2.99 or the like, 1 just passed the input voltage through regardless of adjustment.  I might dig one out and pop it on the bench...

Those ones listed are actually down as boost onverters, so plugging one of those into an iPad will generate a few sparks. They all look the same so it can be pot luck what you get. You may have meant these ?

http://www.ebay.co.uk/itm/Boost-Buck-DC-DC-adjustable-step-up-down-Converter-XL6009-Module-Solar-Voltage/191777597596?_trksid=p2047675.c100009.m1982&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20140328180637%26meid%3D9473a34b18de4af1ab63337625095938%26pid%3D100009%26rk%3D1%26rkt%3D10%26sd%3D272041588474

397

General Discussion / Re: RPi 3 to have built in WiFi

« on: February 29, 2016, 09:53:16 am »

One item of note is the recommendation for a higher capacity power supply over the previous generations - presumably as the base Pi takes more power you need the extra for anything powered by the USB ports.  They recommend going the current recommended 1.2A to a 2.5A PSU.

New recommendation on here
https://www.raspberrypi.org/blog/raspberry-pi-3-on-sale/

Previous power requirements
https://www.raspberrypi.org/documentation/hardware/raspberrypi/power/README.md

398

General Discussion / Re: Battery advice

« on: February 11, 2016, 11:56:17 am »

You could always fit a Charge2 into the aircraft, as it's a permit aircraft.  Then simply plug the PAW and you tablet/phone of choice into the other port.

Then no need to remember to buy batteries, or charge them, just plug in and go.

399

General Discussion / Re: Pi2

« on: January 27, 2016, 09:46:36 pm »

, we have commissioned / worked on a bespoke radio for PilotAware, as we couldn't find one to fit the bill....

 

Last time I heard from Lee the work was to make enhanced version of an off the shelf far east made radio module, as some core elements are being updated it requires complete re-testing to ensure it stays within the legal limits for everything.  This sadly takes time, plus there is the actual package of Pi, DVB dongle, WiFi dongle (and GPS?) etc. to also run through a compliancy lab as a running package.

I wound't get too hung up on 'bespoke', the module was based on a chipset that is well known (if not the most current) so it would be possible for someone to make a compatible module should there be supply issues from the far east in the longer term.

If it is truly hand crafted bespoke I'd be worried as that creates a single point of failure for the entire project and quite a scary thought, potential diversity of supply is key to the long term success IMHO ( the ARF was single source).  There would be little point in having a public and open P3I protocol only to find to interact you need bespoke hardware, it would be akin to a totally closed system like FLARM.  One advantage of a radio from an EU/US supplier would be that they churn out hundreds of thousands of them a year (if not more) even for tweaked versions.  This area of the spectrum has a wide selection available, I saw a number in a few hours at a trade show last year. 

I suppose Lee or his team have experience dealing with far east design and manufacture processes so know how to get round the issues.

400

General Discussion / Re: SD Formating

« on: December 16, 2015, 07:38:34 pm »

I am one of those people who has ditched Microsoft for Apple. Raspberry Pi SD cards can be formatted using iOS Disk Utility and selecting MSDOS FAT for use on general run of the mill Raspberry Pi stuff. Does anyone know if this is OK for PAW or have I got to find a Windows PC and do the formatting through the Formatter program.

You can download a free SD formatter from the SD Association, Windows and Mac versions are available.

https://www.sdcard.org/downloads/formatter_4/

401

General Discussion / Re: Transceiver Interference

« on: December 14, 2015, 10:33:41 am »

After a short first flight with my PAW, we got very bad  interference over the radio(Set to 122.6) at a level that could not be squelched out. Interference was in the form of regular pulses. Intensity appeared to vary, there was a lot of radio traffic and sensitivity of radio changed if it was receiving a carrier prior to someone talking but in quiet periods noise pulses were regular.
To confirm that it was the PAW we removed power from it and all was good, added power and the interference return when the PAW had booted. All worked fine as just an ADS-B receiver, there is no ARF connected to the PAW. We are powering from one of the recommended USB battery. I suspect the interference is coming from wifi. Are there any suggestions on how this interference can be corrected?
Thanks
Barrie

Can you try plugging something else into the battery pack so see if it's the PAW or the power unit?

Some battery packs use boost/buck converters to adjust the LiPo power from the battery (normally around 4v) up to the 5v needed, some of those are pretty effective noise generators. 

402

General Discussion / Re: Broadcasting the wrong position!!!

« on: December 11, 2015, 11:25:57 am »

That really is pretty poor when it just needs to to forward the GPS info.
And we get the privilege of having to pay to have it fixed although I think ours is too old to upgrade anyway.
It's a technology shambles 

It isn't quite as simple as forwarding the GPS info, the NEMA string gives the Lat Long in one format but it has to be mangled to go out in ADS-B format.  In ADS-B the position is split over two packets and uses Compact Position Reporting (CPR).  The document below explains it, starting on page 6.  It is there to save a few bits of data, critical at the time it was developed.  It even matters if it is an even or odd packet pair.

http://www.eurocontrol.int/eec/gallery/content/public/document/eec/report/1995/002_Aircraft_Position_Report_using_DGPS_Mode-S.pdf

Round my way (Cambridge) it's always fun plotting positions as the meridian passes through this area, so people often get their East/West muddled.

403

General Discussion / Re: Custom enclosure

« on: December 09, 2015, 09:09:04 pm »

It's a much bigger volume and the commercial firms offering the higher quality materials seems to be going on overall size of part rather than just volume of material used.   

I'm more interested in your usb port mod.  What skill level is required to pull that off?

Not sure why they would be quoting on sheer volume, unless your design required support material?  A design with large unsupported features would require a multi-head printer and expensive soluble support materials, which would push the price up.

No particular skills required to de-solder the USB socket - a decent vacuum desoldering station helps, but ultimately you could do it with some solder-wick and a basic soldering iron.  Those manual solder-sucker pumps are next to useless though.

The header pins are standard 2.54mm headers, but the spacing of the holes for the USB socket aren't exactly 2.54mm, so arranging them as 2x4 vs 4x2, and a bit of fine trimming of the plastic shroud is required.  The cables use single vertical A-type USB PCB header to connect to the dongles.

Just be careful about this mod and the potential affect on signal integrity.  USB requires a twisted pair for the data wires, and it should also be shielded to prevent both ingress and egress of noise.  There is a potential to quite easily cause corruption of the data on the USB.  At the very least please twist the D-/D+ wires together.

The pinouts for this type of connector are a standard, the attached file is the layout for the Molex connectors I use in my chargers, FYI.

404

General Discussion / Re: Licensing cost

« on: December 05, 2015, 10:52:22 pm »

I believe the licence is there to ensure the continued development of the software underpinning the project.  People throw enhancement requests in, but it takes time and effort to make them happen.

The hardware elements are "open hardware" and all available commercially, even the new radio module in its raw unmounted form.  However the software is what pulls it all together, and for £1 per month (+VAT) is astounding value.
If you wanted to you could "roll your own", but it would take substantially more in terms of time and effort to do and maintain in addition to physically making your own shield to mount the radio module.

The cost of the new shield reflects the time spent in sorting out various issues and I suspect in no part to cover the costs of the required testing to ensure basic CE compliance.  EMC & RF testing isn't cheap, believe me.  Even setting up to do your own pre-compliance checks is an expensive exercise although it can can save £1000's in time at the test labs.

It's a credit to Lee that the price is set at the low level it is IMHO.

405

General Discussion / Re: Download dropbox error

« on: November 08, 2015, 06:15:06 pm »

Oops, we are in the process of moving to a new server, looks like this has just gone up the priorities

Depending on your timescales I'd be happy to host a file until you get sorted. 
I have unlimited hosting so no issues with bandwidth or limits.