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space balloon / circuit help / awful diagram

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cynic

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I have a high altitude balloon project - See the last one here -> Launch DIY Space

Looking at the diagram below - my gumstix computer (with GPS) will periodically read telemetry data over the radio; using text to speech.

This is the optoisolator - SparkFun Electronics - Opto-isolator Breakout

This is the relay - SparkFun Electronics - Relay SPDT Sealed - Mini

When I want to transmit the gumstix turns the GPIO port on (from no power to 3.7 volts / 80 milliamps)

That takes the circuit between OUT1 and the power on the battery to 7.4 volts and 10 milliamps. Not enough to throw the relay - DRAT!

If it did throw the relay then the Push to talk on the radio would be closed and my radio would transmit. After reading telemetry data the gumstix would then turn the GPIO off and that would open the PTT back up on the radio.

Am I exceeding max power inputs on the opto isolator? Is the 10 milliamps output on the opto isolator what I should be seeing?

Eventually I will be using this wiring to ignite a rocket motor (on a separate battery) so I want the opto isolator to prevent damage to the flight computer when firing the rocket motors.

Does this make sense :)
Help - This is only my second project and I majored in Literature :)

 

Sceadwian

Banned
Cynic, just because it's kind of important, did you get FAA clearance for that?
Not getting proper approval for this is criminally irresponsible.
 

Sceadwian

Banned
You mean CFR101?
Sec. 101.5

Operations in prohibited or restricted areas.

No person may operate a moored balloon, kite, unmanned rocket, or unmanned free balloon in a prohibited or restricted area unless he has permission from the using or controlling agency, as appropriate.
US airspace is restricted. Not sure what specific section you're referring to. A bird is not a balloon launched by man.

101.1 says that the exclusions only apply to balloons with a diameter of less than 6 feet, and under a specific weight. The one in the picture from the link you provided is larger than that, and will only get bigger as it goes up. As near as I can tell your device doesn't meet any of the requirements to be waived from getting FAA clearance.
https://rgl.faa.gov/Regulatory_and_Guidance_Library%5CrgFAR.nsf/0/4D5DB7354C4541EE86256EEC004EC67A?OpenDocument

Seriously, is this legal?
 
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cynic

New Member
Well the easiest way to look at it is part 101.1 - FAR Part 101 Sec. 101.1 effective as of 05/26/1970

(a) This part prescribes rules governing the operation in the United States, of the following:
<SNIP>
(4) Except as provided for in Sec. 101.7, any unmanned free balloon that--
(i) Carries a payload package that weighs more than four pounds and has a weight/size ratio of more than three ounces per square inch on any surface of the package, determined by dividing the total weight in ounces of the payload package by the area in square inches of its smallest surface;
(ii) Carries a payload package that weighs more than six pounds;
(iii) Carries a payload, of two or more packages, that weighs more than 12 pounds; or
(iv) Uses a rope or other device for suspension of the payload that requires an impact force of more than 50 pounds to separate the suspended payload from the balloon.

Thus, if the payload is under 4lbs there are no rules except for part 101.7 - FAR Part 101 Sec. 101.7 effective as of 06/29/1963

(a) No person may operate any moored balloon, kite, unmanned rocket, or unmanned free balloon in a manner that creates a hazard to other persons, or their property.
(b) No person operating any moored balloon, kite, unmanned rocket, or unmanned free balloon may allow an object to be dropped therefrom, if such action creates a hazard to other persons or their property.

So it appears that so long as the payload is under 4lbs and one uses good sense that all of the rules are followed.


Back to the original question - Any help with the optoisolator?

Thanks!
 

kchriste

New Member
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I have a high altitude balloon project - See the last one here -> Launch DIY Space
That's a really cool project! Too many mountains and ocean to try around here.

Though it isn't the immediate problem, you need a diode across the relay coil. This will protect the transistor on the opto from the voltage spike produced when the relay is turned off.
If you were using a plain jane opto, you probably wouldn't need the relay at all. You may be able to use the existing in this way if one side of the radio's PTT switch is connected to battery minus.
Do you have a volt meter?
Can you read a schematic?
 

Sceadwian

Banned
cynic, you have to satisfy ALL portions of the code, you can't just pick one and say it's okay.

You conveniently snipped the portion of the code that your balloon violates.
(1) Except as provided for in Sec. 101.7, any balloon that is moored to the surface of the earth or an object thereon and that has a diameter of more than 6 feet or a gas capacity of more than 115 cubic feet.
You still have to satisfy EVERY condition. Not just the ones you feel like.
 
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kchriste

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I don't think his balloon is "moored to the Earth". That would be one heck of a long rope and a very tangled mess when it came down! :D
 

Sceadwian

Banned
Please don't take offense to this kchriste, but I swear I'm gonna punch the next person that posts without reading previous posts and links in full. Cynic shouldn't be coy and hide behind the weight requirements siteing birds can weigh more, birds don't go ANYWHERE NEAR that height, they also at that height don't have such a cross sectionial area to hit, nor are they made out of modern high strength fabrics that could easily foul control surfaces.

Code of Federal Regulations


Sec. 101.1

Part 101 MOORED BALLOONS, KITES, UNMANNED ROCKETS AND UNMANNED FREE BALLOONS
Subpart A--General

Sec. 101.1

Applicability.
 
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kchriste

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You conveniently snipped the portion of the code that your balloon violates.
Quote:
(1) Except as provided for in Sec. 101.7, any balloon that is moored to the surface of the earth or an object thereon and that has a diameter of more than 6 feet or a gas capacity of more than 115 cubic feet.
I don't understand your post in the context of this thread. What has the quote above got to do with your claim that he is in violation of the FAA rules?
And yes, I did read the links. And no, I'm not a Lawyer, but it looks like as long as the payload is less than 4 pounds and it is a free balloon etc, it is OK. Here I'll quote the whole thing. Highlight in bold the part I'm not getting, because I don't see the problem:
Sec. 101.1

Applicability.


(a) This part prescribes rules governing the operation in the United States, of the following:
(1) Except as provided for in Sec. 101.7, any balloon that is moored to the surface of the earth or an object thereon and that has a diameter of more than 6 feet or a gas capacity of more than 115 cubic feet.
(2) Except as provided for in Sec. 101.7, any kite that weighs more than 5 pounds and is intended to be flown at the end of a rope or cable.
(3) Any unmanned rocket except:
(i) Aerial firework displays; and,
(ii) Model rockets:
(a) Using not more than four ounces of propellant;
(b) Using a slow-burning propellant;
(c) Made of paper, wood, or breakable plastic, containing no substantial metal parts and weighing not more than 16 ounces, including the propellant; and
(d) Operated in a manner that does not create a hazard to persons, property, or other aircraft.
(4) Except as provided for in Sec. 101.7, any unmanned free balloon that--
(i) Carries a payload package that weighs more than four pounds and has a weight/size ratio of more than three ounces per square inch on any surface of the package, determined by dividing the total weight in ounces of the payload package by the area in square inches of its smallest surface;
(ii) Carries a payload package that weighs more than six pounds;
(iii) Carries a payload, of two or more packages, that weighs more than 12 pounds; or
(iv) Uses a rope or other device for suspension of the payload that requires an impact force of more than 50 pounds to separate the suspended payload from the balloon.
(b) For the purposes of this part, a gyroglider attached to a vehicle on the surface of the earth is considered to be a kite.
 
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kchriste

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Sceadwian

Banned
kchrite, the payload isn't the question the balloon itself is too large.
 

kchriste

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The size restriction only applies to a balloon that is moored to the surface of the earth.
They do not specify a maximum size for a unmanned free balloon.
 

kchriste

New Member
Forum Supporter
Yes, there would always be the liability if the balloon or payload damaged someone else's property or injured someone. America is a pretty litigious society and I'm sure you'd be sued if something went wrong.
 

cynic

New Member
ok..... so FARs aside which are fine. Lots of people make high altitude balloons every year. It's safe, it's legal and its harmless......


Help with the circuit :)
 

kchriste

New Member
Forum Supporter
Perfectly happy to move on from the "FAR side".
Please reread my previous post which got buried in the noise. I had a few questions for you there.
 

cynic

New Member
That's a really cool project! Too many mountains and ocean to try around here.

You probably could. You can exchange peak altitude for ascent rate and there are existing program that will predict the balloon's flight path. Thus, you can predict the flight with some degree of accuracy.

Though it isn't the immediate problem, you need a diode across the relay coil. This will protect the transistor on the opto from the voltage spike produced when the relay is turned off.

Hmmmm.... I have gotten inconsistent results with this setup and now I wonder if I have fried the opto-isolator board? As I understand, A diode is just a one way valve for electricity. would the diode go in line between out1 and the relay?

If you were using a plain jane opto, you probably wouldn't need the relay at all. You may be able to use the existing in this way if one side of the radio's PTT switch is connected to battery minus.
Do you have a volt meter?
Can you read a schematic?

I do have a volt meter. I can probably figure out a schematic. One side of the PTT is not connected to the battery negative. The PTT is really just and switch that interrupts the mic in line; its on the power lead of the mic in. Hopefully that makes sense.
 

kchriste

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Hmmmm.... I have gotten inconsistent results with this setup and now I wonder if I have fried the opto-isolator board?
It is possible, but more likely because the opto doesn't have enough drive capability to activate the relay. Looking at the schematic of the opto PCB, I see some 2n2222 transistors being driven via an isolator and 10K pullup resistor. The 10K resistor means that the transistor is only getting apx 0.7ma of drive current when the battery voltage is 7.5V. The 2n2222 won't have enough beta (gain) to turn fully on (saturate) so won't apply the full voltage across the relay coil. You could test this by measuring the voltage across the relay coil with your volt meter. It would be best to have the radio turned off because the RF will probably cause the meter to give a false reading.
If the voltage is too low (Less than 5V) then we could add a transistor to boost the current. What types, if any, do you have on hand?
As I understand, A diode is just a one way valve for electricity. would the diode go in line between out1 and the relay?
It would go across the relay coil with the stripe facing the (+) battery side. Any of the 1N400x (Where x is a number) diodes will work. So will the common 1N4148 or 1N914.
One side of the PTT is not connected to the battery negative. The PTT is really just and switch that interrupts the mic in line; its on the power lead of the mic in. Hopefully that makes sense.
That makes sense. A lot of portable radios have the PTT in series with the powered electret mic element. They sense the mic bias current draw when the switch closes and then key the radio. Saves a wire in the mic cord. A relay contact is best for this type of setup.
 
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