Space Balloon - first project

Projects General Guidance
1

Hi all...

This will be my first Arduino project - and will be a huge learning curve. At present I can program in visual basic, SQL, basic html and have a mild appreciation for C.

I know this is going to be a massive project but the benefits will be worth it, and I would like to turn the end result into a polished project to share with the entire community / produce some fabricated PCB's for modular use.

The requirements would be this (perhaps shown better in a graphical format) :

  1. Lithum power source that is seperate from the arduino and charged using solar panels. Circuit required to maintain charging process. Regulated output at a set current / voltage as required by the arduino and peripherals. There should be a way for the arduino to read / record the charge of the cells without having to manage it (data logging). http://www.ebay.co.uk/itm/PCB-Charger-for-4-Packs-3-7V-Li-ion-Li-Lithium-18650-Battery-Rechargeable-2-5A-/261076731018?pt=UK_BOI_Electrical_Components_Supplies_ET&var=&hash=item3cc962c48a

  2. Modular GPS input x2 - so that the user can change the items being used, with their being 2 for redundancy.

  3. GPRS / SMS technology using a sim card arduino shield. I have seen people using ericsson T68 with serial connectivity. I would rather use a shield that allows for SMS to be sent, again this must be modular so that the shield can be change - should receive an input from set pins and produce an SMS output.

  4. Shutter camera control. I do not want to use the canon hack approach. I would rather incorporate a shutter control from arduino. This should be modular - set pins produce a timed signal to take a picture every (n) seconds.

  5. Modular sensors. I would like to record barometric pressure, temperature etc. There are shields available for this I believe.

  6. SD card (or micro sd card) shield for data logging purposes - all information related to altitude, pressure, temp, battery performance, pictures taken, time is to be recorded.

  7. Modular radio transmitter module. This should receive an input form set pins and output whatever is recieved. I have seen several options for arduino compatible radio modules.

I have also been looking here Home - TimZaman.com for inspiration but this is getting very niche with set technology. I would like a truly modular approach with several options for the hardware so that people can build their own based on what they have. I will happily invest several weeks of time coding a robust, flexible solution that the user can configure using a single file. The end result would be fantastic.

Desires outputs would be SMS signalling of position from GPS as set interval, along with altitude and other telemetrics. When SMS is out of reach the radio module will continue to transmit this information. All output should be compiled into a KML file for spatial viewing on google mapping services, with each data 'point' containing the detailed telemetrics and timings and picture count. This will allow for pictures to sync up with the data in mapping.

I will be producing an off the shelf heated packaging solution with paracute and balloon. I would like to develop a way of recording when the balloon pops / detach the cable.

Any ideas / help / thoughts welcome :slight_smile:

http://www.timzaman.nl/wp-content/uploads/2011/03/hohoho-i-schematic1.jpg

2
  1. GPRS / SMS technology using a sim card arduino shield.

This is a violation of both FCC regs un the United States, as well as common sense. Cell phones do not work well at altitude snd they cause problems with cells for hundreds of miles. Balloons frequently land in areas with no cell coverage, which mean you have no tracking.

There are also FAA regulations to deal with.

If you're not in the US, you still have some equivalent of the FCC and FAA. Learn the rules.

A balloon operates in very cold low pressure conditions. A lipo battery will return swollen, to the point where rupture of the case is a concern. They typically aren't designed to operate in a vacuum.

Typical small radio modules have ranges measured in feet or meters, not miles. They are not sufficient for a balloon flight that may cover 100 miles over ground. They also are designed for room temperature, not -40.

I recommend you do some googling. Start with amateur radio high altitude ballooning.

-j

3

I do understand your response, all of these points are based on the technology 90% of high altitude balloon enthusiasts are using.

Lithium battery - the only items that will remain active at lower temperatures
SMS broadcast - to be used within legal atltitudes
Radio - working with a high gain antennae for several KMs
GPS - several will work above 60,000 feet (specific modules / settings).

This is all documented and proven on the links I provided. There have been no rupture issues reported with lithium. All items are encased in polsyrene which results in around -40oc temp, this can be managed.

I have googled extensively so now coming here with my findings to get some help on the approach forward. Did you check any of the links provided?

4

Yes, I saw the links. My comments drew on my personal experience with around 75 flights over the last 10 years.

FYI, a sample size of 1 doesn't "prove" anything. So it worked one time - big deal. Did it work because of what you did, or in spite of it?

Cell phone tracking - bad idea, don't care how many MIT students or bloggers did it. It's unreliable and if it is powered up at altitude it can cause problems with the entire cellular network on the ground. Cell towers use phased arrays to direct the gain pattern down, toward the horizon. As a result the only towers that can hear you are too far away to be effective. When a balloon is at 100k', the horizon is almost 400 miles away. When we fly we cover the entire southeastern United States at max altitude. Want to cause cell phone problems for millions of people?

10mW radiometrix 70cm radio - 10mW is weak, I recommend 100mW minimum ERP. Depending on your terrain, 500mW may be a better minimum. Based on personal experience with 10mW FM radios flown on high altitude balloons.

Lipo - I've seen them swell. Sometimes they do, sometimes they don't. Is your battery pack rated for -40C? -70C? it may get to -70C outside, and it will get to -40C almost guaranteed. If you use lipos you need thermal management. Recommended power source is lithium primary cells - e.g. Energizer lithium AA, CR123A photo cells, specialty 3.7V lithium primary cells. Works every time. Another issue with lipos is age and condition. Are you using some old RC junker lying around, or are you buying a battery pack for the mission? If you're buying one, may as well buy primary cells.

The radiosondes that fly every day use wet cells (that's a data point, not a recommendation). In addition to generating electricity they also generate heat - keeps them alive during flight. (Those I've seen are also messy.)

Study the KISS principle. Rather than a single complex tracker with multiple GPS units and multiple radios (and many places where you have a single point of failure), use two completely separate independent trackers. We put 'em in separate payload packages. If your payload requires resources that the trackers have, duplicate those resources instead of interconnecting with the tracker in order to reduce failure points.

Test the system as it would fly as closely as possible. Use flight hardware configurations (batteries, packaging, etc) and throw it all in the freezer for 3 or 4 hours.

Other recommendations depend on the payload. E.g. if you're imaging think about condensation, etc, because you will be traveling through air at various temperatures and relative humidities, and you will encounter condensation. Heaters and/or moisture absorption are indicated.

-j

5

I'm working trhough a similar project though I think less ambitious.

Solar panels - This is a tradeoff between the weight required to get the required current and the weight of an equivalent battery pack to provide 4-5 hours of life for your payload. I've toyed with a small panel to provide at least some current to extend the battery life but balloon altitude is a direct function of payload weight so I will be doing some calculations to see if its worth it.

Cameras:
I'm choosing to send a Go Pro aloft to record the event in high quality for the duration (at a low frame rate) and I am trying to configure a LinkSprite JPEG camera to take periodic images for transmission to the ground. Personally I'm having difficulty getting the Linksprite to work (it hates me) but I'm still plugging away.

Transmitters:
I'm using xbee pro transmitters for prototyping (putting the payload on RC airplanes, etc.) and there is a high powwer, pin compatable transmitter with a 40 mile range that I'm considering for the payload.

Batteries:
I've never seen a LiPo expansion issue mentioned before but it seems that is something that can be checked out in advance with a vacuum chamber. I purchased a 6AH Lipo set from SparkFun and depnding on how many amps the payload draws I'm hoping that is sufficient to power the payload for the flight as well as transmitting a beacon once its back on the ground.

Good luck.
Jim

6

@kg4... You're right of course cell phones don't work well at high altitudes. But they do NOT cause a problem for others. People prove this every day they fly with one on. I have tested many cell models myself flying, and they do not reliably reach a site 50 miles away. If they do not reach any site, then certainly they cannot interfere with one. The reason for this is that adjacent cells use different frequencies. A neighbor 3 down also uses different frequencies. So a mobile phone can be used to track a balloon on it's way down before it lands. Assuming there is a town or cell site within about 20 miles.

Sometimes Lipos swell at sea level. I believe you're right they do it more often at 60,000ft. Still it is rare above -40C.

7

I will second the recommendation for lithium primary cells. Watch for a sale on Li AA cells and build a big battery pack out of them.
Do not bother with solar cells. They are expensive and fragile, and do not generate enough power to bother with.
For heat, throw in a couple of those cheap iron-air hand warmers. A couple of these bad boys will give you enough heat to keep the electronics running at only a few dozen grams of weight.
http://stn3.headgap.com/hothands/FMPro?-db=Ordershh.fp3&-format=products.htm&-new

I do not understand why you're down on CHDK. It works great, and turns your camera into a totally autonomous instrument package. All your other electronics could fail and you'd still get a slew of pretty pictures.

8

I have tested many cell models myself flying, and they do not reliably reach a site 50 miles away. If they do not reach any site, then certainly they cannot interfere with one.

Just because they don't connect does not mean they don't cause problems. My wifi network did not "connect" with my cordless phone, but every time someone talked on the phone my wifi network would stop working.

Just because your cell phone antenna is too crappy to receive a signal, doesn't mean the ground stations don't hear you and expend resources trying to talk to it.

For heat, throw in a couple of those cheap iron-air hand warmers.

At altitude, no air == no heat. They will generate heat on the ground, and they'll help retain heat, but they will stop generating heat as air density drops.

-j

9

Transmitters:
I'm using xbee pro transmitters for prototyping (putting the payload on RC airplanes, etc.) and there is a high powwer, pin compatable transmitter with a 40 mile range that I'm considering for the payload.

Are you talking about the Digi 9XTend? Our guys flew them and had solid comms out to 42 miles, at which point a mountain got in the way.

-j

10

@kg4- You've got it backwards. Most mobile phones can receive a signal much further away then they can transmit. It's easy to prove this in the ocean offshore. You have a strong signal receiving, sometimes 2 bars, but you cannot make a call. Therefore my theory is correct, if you can't receive, you can't interfere significantly.

11

kg4wsv:
My wifi network did not "connect" with my cordless phone, but every time someone talked on the phone my wifi network would stop working.

That's a common problem caused by two signals on the same frequency. However, if your DECT handset had been too far away to connect to the base station, then I think it would also have been too weak to interfere with the WiFi signal at the same range. The bad news is that signal strength falls off with range; the good news is that interference strength also falls off with range.

12

Most mobile phones can receive a signal much further away then they can transmit. It's easy to prove this

You prove little counting the bars on a cell phone or the inability to make a call as data points.

The US FCC believes that it is a problem, and in spite of it being a government bureaucracy they do actually possess some technical knowledge on the subject.

Even if a device does not have the signal strength or the correct modulation to "connect", it can raise the noise floor on the frequency it is using.

-j

13

kg4wsv:
At altitude, no air == no heat.

No air also means no buoyancy, ie: a balloon cannot get there.
Those things do not need any specific partial pressure of O2 to work. They will generate some heat wherever this is some O2, and buddy's balloon is not going to exit the atmosphere.

14

No air also means no buoyancy, ie: a balloon cannot get there.

At 100k' you are above 99% of the atmosphere. The sky is black; there's not enough air to turn it blue. There is enough air to cause a 60" parachute to inflate, but not enough for said parachute to induce much drag (so that the first 30,000' of descent takes about 90 seconds). It is, for practical purposes, a vacuum.

They will generate some heat wherever this is some O2, and buddy's balloon is not going to exit the atmosphere.

Again, this is not my opinion, this is observed flight data. These things do not produce effective heat at altitude. It is possible that they are still working but there is no air for thermal conductivity, or maybe the chemical reaction stops due to the cold, or some similar issue, but you don't get heat out of 'em.

-j

15

Just this week they changed the rules about electronics on planes, this includes mobile phones. The FCC had some input on this decision. So by your own admission, they must have some technical knowledge to make this decision! It's been on the news.

16

You are confusing the FAA with the FCC>

The FAA is examining rules concerning electronics on planes. The ban on electronics are FAA rules concerned with interference with flight systems.

The "phone" part of cell phones are not, AFAIK, part of the discussion, nor is the FCC restriction on airborn altitude use of cell phones.

-j

17

I'm just saying the FCC must have some input on this topic, since they have technical knowledge you said. Obviously they don't expect every passenger to be familiar with Airplane mode on every phone. Therefore, the phones will be on. The FCC accepts this and does not discourage it in their discussions. Regardless of the rules, there will be, and already are, 100's of passengers with their phones on each day. Has this caused a problem? Has there been an effort to stop it from corrupting our land based systems?

Here's a story which may help. In the 1970's I used to talk to the pilots from the front/back of the plane with a 2m radio. Never did they discourage me from doing so. This is on multiples planes and pilots. Are they trying to tell me our navigation systems have gotten so much worse in 40 years? More sensitive? 2m at 5w is less powerful and disruptive than a mobile phone?

I also used repeaters from the air. Rarely did I bring up 2 at once, and they're often only 100 miles apart. This is much different from cell phones whose range are significantly less.

18

@kg4wsv - Yeah, That's the radio set. Its good to hear someone who actually achieved the rated mileage. Most times you hear the stories about how a radio only worked to half the advertised distance.

19

Those ranges can be tough to estimate, depending on the physical environment (antennas, attenuation, multipath reflections, all that good RF stuff).

That 42 mile configuration was a standard rubber duck on the flight radio and a yagi of some sort at the ground station. I vaguely recall the yagi had around 8 elements???

If you use a yagi, keep the coax short and use a long serial cable. Coax attenuation is higher as the frequency goes up (9XTend uses 900MHz), so it's to your benefit to get the radio as close to the antenna as possible.

-j