PilotAware
British Forum => Technical Support => Topic started by: alan_d on January 23, 2018, 05:00:49 pm
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I'm working on a custom 3D-printed case design to hold the PAW hardware, a Pi battery board and a screw-on SMA mounted RTL-SDR antenna, more info below. The goal is for all the parts to be self-contained in one box without needing external cables to work.
Is there any reason for the RTL-SDR and PAW 'bridge' antenna (or whatever the correct name is) not to be close to each other? Currently I have them both on the same face of the case.
Initial testing with the Pi battery (like this: http://amzn.eu/585S6ia) shows it will run the PAW kit for about 2.5 hours. Obviously external power can be connected to give longer.
The case has openings for each port, SD card slot and all LEDs, as well as airflow holes. I've provided support for the USB GPS dongle internally (minus it's plastic housing) rather than relying purely on the USB port to support it.
Once i've finalised the design i'll post pictures - and if anyone would like a case with or without battery provision I can sell them cheaply :)
And if anyone has suggestions of what a custom case should include, let me know!
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Alan,
The antennas can be placed fairly close to each other without causing any issues. There are several examples on the forum where users have put all the bits in one box, or simply cut down the 1090MHz antenna (which is receive only) and its cable and sat it on top of the standard case near the 869MHz P3i antenna to keep the unit more 'contained', without any reduction in system effectiveness.
It will be good to see your design once you get it finished.
Regards
Peter
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Initial testing with the Pi battery (like this: http://amzn.eu/585S6ia) shows it will run the PAW kit for about 2.5 hours. Obviously external power can be connected to give longer.
And if anyone has suggestions of what a custom case should include, let me know!
Sounds interesting Alan.
I think it needs a bigger battery. For example :- I'd want to be able to fly 1.5 hrs - consume burger - fly home for 1.5hrs
3 hrs run time would be an absolute minimum, 4 would be better.
ATB
Deker.
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I think it needs a bigger battery. For example :- I'd want to be able to fly 1.5 hrs - consume burger - fly home for 1.5hrs
3 hrs run time would be an absolute minimum, 4 would be better.
I used an off-the-shelf battery for convenience. With a slightly bigger case it would be possible to use 2x 18850's to give longer run-time. I use these with Pi3's in another project i'm involved with (to scan runners with RFID tags at outdoor events) and we get about 28 hours from 6x quality 18850's running the Pi3, a 3.5" screen and WiFi connected.
Based around the current battery, it could be connected to the plane's fag-lighter socket or a power-bank to extend run-time or re-charge the battery.
The current case design is 62x128x42mm all-in.
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Is there any reason why you cannot make a trap door for the battery so that it can be swapped. I don't think many flights will be over 2 hours, so One battery outbound and another for return?
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Is there any reason why you cannot make a trap door for the battery so that it can be swapped. I don't think many flights will be over 2 hours, so One battery outbound and another for return?
Yes that's possible.
I'll finish the current design based around a standard Pi battery first then look at alternatives. A dual 18850 holder is probably ideal for this.
Current headache is that the power switch on that Pi power board is bypassed when plugged into charge - which means that the Pi etc is powered up when charging, and that charging takes longer than it needs.
Workaround is to remove the on-board switch and fit a DPDT switch to the case wall to both switch on the power module and feed the Pi, so when in the off position then it will charge the battery and NOT power the Pi.
As I can't find a suitable small rocker switch it'll have to be a slide switch - so design on-hold until switches arrive to design mount in case for it...
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Alan,
The antennas can be placed fairly close to each other without causing any issues. There are several examples on the forum where users have put all the bits in one box, or simply cut down the 1090MHz antenna (which is receive only) and its cable and sat it on top of the standard case near the 869MHz P3i antenna to keep the unit more 'contained', without any reduction in system effectiveness.
It will be good to see your design once you get it finished.
Regards
Peter
Thanks Peter. I hope to have it finished to test-fly it at the weekend. Will upload photos etc when done.
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OK, here's the current case I designed & 3D printed, for a one-box solution without cables everywhere.
It includes a standard Pi battery (Like this: http://amzn.eu/fcGY5lz (http://amzn.eu/fcGY5lz)), and a SMA pigtail antenna mount + antenna from here http://amzn.eu/6UoJcMx (http://amzn.eu/6UoJcMx) for the RTL-SDR.
I removed the case from the GPS dongle to make it fit. There is support in the case wall for the GPS board.
The battery lasts about 2.5 hours, and it has a standard micro-USB connector for charging.
Rather than an external USB to micro-USB cable for power, I soldered the wires internally, via the switch.
The lid is dual-colour 3D printed. I tried the same with the case for the lettering but the results aren't great.
For updating you can get to the ethernet socket with the lid removed - I did this without issue today.
If anyone is interested in one of my cases, I'll list them on ebay in a few days. I'm currently waiting for proper sized M2.5 pillars for mounting between the Pi and the lid to arrive, and will probably sell it as a kit with the pillars, switch, screws etc.
And if anyone would prefer a version without the battery, i'll work on a version like that soon.
Any suggestions to improve it further welcome. I've already recessed the power switch by a further 2mm in the design, which will be in the next print.
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Newbie here (so new my PAW hasn't even arrived yet), but as fly open cockpit in a shared machine I plan to keep this very mobile and been reading this thread with interest as it would beat faffing around with cables etc in the map pocket. Be interested to see how this box works out and get one of you if sold as a kit that I can transpose my unit into.
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Very neat solution Alan (D). Have you tried your PAW inside this box yet and was the GPS reception affected? What are the box dimensions and the overall weight, with the Pi battery added.
I think you might do quite well from this :)
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Have you tried your PAW inside this box yet and was the GPS reception affected? What are the box dimensions and the overall weight, with the Pi battery added.
GPS when I tested it at home (with the lid on, on my windowsill in the middle of a housing estate) was showing 6 satellites. I expect more with a decent view of the sky.
I kept the lid thin over the GPS antenna ;) lid picture attached.
Box dimensions are 62x128x44mm
Total weight including both antennas is 327g
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I'm VERY interested in this
do let us know the instant they're available on a well known bay! :)
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I'm VERY interested in this
do let us know the instant they're available on a well known bay! :)
Will do. As the pillars are needed to mount the lid, I need to wait until they arrive before I can sell it as a kit. In the meantime i'll get on with printing some and work out the costs.
Any preference of colour? I tried one in black but it looked a bit boring!
Also (to the PAW staff), what is the font of the 'PilotAware' text so I can use the correct one for the lid?
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Hi Alan,
Your case looks very professional, I’m impressed!
A couple of issues you should consider though, mainly regarding ventilation. The SDR dongle tends to run hot (which has caused a couple of failures, probably linked to running in enclosed spaces) and will run even hotter shut inside your case. The Pi may also get hotter than is good for it unless some ventilation is supplied.
The Stratux cases (see Amazon) incorporate passive ventilation slots and also a fan, in fact the case has just been updated and the Mk.II (or maybe that should be Mk.III) version now incorporates 2 fans. I would suggest at the very least some ventilation slots and removing the case from the SDR dongle if you wish to avoid problems.
Best Regards
Peter
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Hi Alan,
Your case looks very professional, I’m impressed!
A couple of issues you should consider though, mainly regarding ventilation. The SDR dongle tends to run hot (which has caused a couple of failures, probably linked to running in enclosed spaces) and will run even hotter shut inside your case. The Pi may also get hotter than is good for it unless some ventilation is supplied.
The Stratux cases (see Amazon) incorporate passive ventilation slots and also a fan, in fact the case has just been updated and the Mk.II (or maybe that should be Mk.III) version now incorporates 2 fans. I would suggest at the very least some ventilation slots and removing the case from the SDR dongle if you wish to avoid problems.
Best Regards
Peter
Peter - yes additional holes are already on my 'to do' list. I added some to the lid already as you can see on the photos. I'll add some around the case walls also before the next print.
I've tried the lid ones at 3mm and 2mm - the 3mm looked a bit big, so the photo above is 2mm holes. Will probably use the same size for the walls.
Removing the SDR case will also help it fit better next to the wifi dongle, so will do that soon.
I'll upload some photos of a 'holey' case when complete.
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Hi Alan, would moving the switch allow enough space for a fan?
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Hi Alan, would moving the switch allow enough space for a fan?
Yes, that's possible. The switch could go horizontally on the other side below the GPS dongle.
Something like a 30mm 5v fan?
It would shorten the battery life a bit, would need to test to see by how long...
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Interesting ‘enclosure’, Alan.
But I am not sure about your external connector slots, as they are too easily disturbed or disconnected. I have gone for the opposite philosophy, of having all the connections inside the box so they cannot be disturbed. And the result is below, with just three leads comming out. The dc converter is inside the box too.
(Update: I see you are working with a 5v internal battery, which makes things simpler. Mine is for a 12v external battery.)
If I was better at engineering, I would probably have screw connectors on the exterior of the box for the two aerials, like you have, to make removal of the box for servicing easier. (The aerials are remote, and fixed to the airframe.)
Roger
(https://image.ibb.co/m2zaTm/IMG_0857.jpg)
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Alan
Nice work
Have you done any work on testing the Lipo battery. These can get very nasty if not charged right and cause fire?
Regards
Keith
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But I am not sure about your external connector slots, as they are too easily disturbed or disconnected. I have gone for the opposite philosophy, of having all the connections inside the box so they cannot be disturbed. And the result is below, with just three leads comming out. The dc converter is inside the box too.
Because of the internal battery and wiring between the battery module and the Pi, there is no need for any connectors in normal use. Just switch on and leave it alone.
Only connect to charge it - typically on the ground.
Have you done any work on testing the Lipo battery. These can get very nasty if not charged right and cause fire?
The off-the-shelf Pi battery module is an existing tried-and-tested design, with the battery charge controller etc on-board. Full info here: http://www.raspberrypiwiki.com/index.php/RPI_Lithium_Battery_Expansion_Board_SKU:435230
There is a red charge LED on the opposite side of the board, and a hole in the case to match. It charges from a micro-USB cable (the same as you usually use to power the PAW).
It takes about 2 hours to charge from flat, and automatically stops when full.
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If you were looking to run 2 or 3 LiPo batteries in parallel to increase capacity, without monitoring each cell during charging, then things could get quite interesting if a cell were to degrade. That board is designed to charge a single LiPo cell, so it would be interesting to know what capacities and topologies it supports.
I would be *very* careful about putting a modified unit in a cockpit without some serious testing, including emissions, as the base board seems to have no CE mark. If you looking to sell these in the future you will legally have to prove compliance with the various regulations even with an unmodified unit.
Apart from that, neat idea, there are a few rapid prototyping / small run companies that can produce things like that in small quantities (1-100's) quite quickly should you decide to take things further.
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I would be *very* careful about putting a modified unit in a cockpit without some serious testing, including emissions, as the base board seems to have no CE mark. If you looking to sell these in the future you will legally have to prove compliance with the various regulations even with an unmodified unit.
Good point. I don't see the point of re-selling parts that anyone can buy from Amazon, only the case and hardware to assemble it.
I'll design a version of the case without the battery board also, when I get time!
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Hi Alan, would moving the switch allow enough space for a fan?
Yes, that's possible. The switch could go horizontally on the other side below the GPS dongle.
Something like a 30mm 5v fan?
It would shorten the battery life a bit, would need to test to see by how long...
I was thinking of the fans used in the Statux case, some of us have a few kicking around :) which measure 30mm square, and are 5v 0.2A
If you switch to low power RTL-SDR you will be better off, just :)
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I was thinking of the fans used in the Statux case, some of us have a few kicking around :) which measure 30mm square, and are 5v 0.2A
If you switch to low power RTL-SDR you will be better off, just :)
Yes, I have one here, also from a Statux case ;)
I'm playing with the design now to move the switch to the opposite side, turn it 90, then mount the fan where the switch was.
I'd say a few holes at the antenna end of the box should encourage airflow from the fan past the dongles, battery voltage controller and Pi then out by the antennas.
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If you were looking to run 2 or 3 LiPo batteries in parallel to increase capacity, without monitoring each cell during charging, then things could get quite interesting if a cell were to degrade. That board is designed to charge a single LiPo cell, so it would be interesting to know what capacities and topologies it supports.
I would be *very* careful about putting a modified unit in a cockpit without some serious testing, including emissions, as the base board seems to have no CE mark. If you looking to sell these in the future you will legally have to prove compliance with the various regulations even with an unmodified unit.
This is one area that I have concerns. I have spent a lot of time around LiPos over the years, and a had a few that puffed up, but not caught fire. They frighten me. I use the latest hi-tech chargers, but this is no guarantee that it will be safe. In an aircraft, I would prefer to see Lithium-Ion batteries (LiFePO4), or 4 Eneloop AA cells, and charged away from the unit. Along with extended flight time, that was why I asked about a design with removable batteries.
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What about packing those LiPos into a firesave cover, like they are for charging? Would mean bigger case, but for safety?
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What about packing those LiPos into a firesave cover, like they are for charging? Would mean bigger case, but for safety?
The aim is to have a charging system designed to handle the cells proposed, looking to add in something to contain the result if that isn't done is kind of the wrong approach. These cells can fail not just during charging, the design needs to cater for errant cells.
Its really a case of taking the hit and always doing the right thing with battery technology.
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Update...
The nice people at Pilot Aware contacted me to advise that 'PilotAware' is a registered trademark, so they would not allow me to write 'PilotAware' on my case, but I could sell it as a 'Case for PilotAware'.
So, I've removed the black text from the case lid.
Also, as a few people here and PilotAware themselves have concerns over the lithium battery used in the Pi power module, I have designed a battery-less version of the case, pictures below, complete with 30mm cooling fan.
The fact that this is the same battery technology used in most power banks that are the usual method of powering kit like this when the aircraft doesn't have a socket, and those are considered safer seems a mystery to me, but OK..
Conveniently, there are 5v and GND pins on the PilotAware module nearby which are ideal for powering the fan. I'm waiting for some short USB plugs to arrive to see if they will clear the fan as a plug-and-play fan power option. Space above the SDR dongle is tight.
If anyone is interested, I should be able to offer this as a kit complete with fan, antenna/cable and fixing hardware soon, or just case + hardware sooner if you have your own antenna etc.
I modified the original battery version to move the power switch and add a fan, for anyone who might be interested in that version, and the associated risks. :-\
I need to confirm the costs of the SDR antenna/cable, fan, hardware etc, but i'd expect the complete case kit to be in the region of £20-£30 if anyone's interested.
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All, the design has evolved a bit to allow a USB connected fan, but I finally now have all the parts so they are listed on ebay :)
https://www.ebay.co.uk/itm/162932416827
Alan.
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Looks good, will no doubt pick one up once I can convince others to share the PAW so I can stop paying for it all myself :)
Quick Q - why have option without lugs?
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Quick Q - why have option without lugs?
Yes, I mentioned it in the item description. Default option is without lugs. I'll change the photos to show a lug-less version as the primary photo later.
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Ignore me - was thinking lugs were the stand offs for some reason, not the part on the case for mounting :-[
back to bed for me!
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It will be good to see your design once you get it finished.
Peter
Peter, yours was posted today, hopefully with you tomorrow or Friday.
Attached are pictures of your black case with my PAW bits fitted as well as a version with mounting lugs. I sent you a different lid however as I wasn't happy with the finish of the one pictured below.
Note, you need to spring the case walls apart a little when fitting the Pi/bridge in order to clear the audio socket, while you slide it towards the P3I antenna socket hole.
The case lid is held on with the 4 screws into the Pi mounting pillars, and a block / latch at the fan end - so it needs to slide into place. Carefully check the fan wires aren't pinching on anything.
Let me know how you get on with it and any suggested improvements.