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LaunchPad AlTImeter Technical Support Forum

Discussion about deployment systems including altimeters, timers, air speed flaps, servo systems, and chemical reactions.
blannoy
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Re: Static pressure holes

Post by blannoy » Mon Jan 05, 2015 8:10 am

U.S. Water Rockets wrote:
blannoy wrote:Hi,
I just tested it again with higher pressure to start with. This time it worked every time for the three launches.
It seems that it opens quite a bit before apogee. I assume this is unavoidable. The flights were all very stable and there was barely any wind. Could this be due to the static pressure holes? I could put in a delay on the assumption that the starting pressure is always the same.
The reported altitude is way to high (usually 4 digits starting with 10 of 11, so I assume this to be around 1000 feet). Visually I would estimate the height around 60 to 70 meters but it's hard to guess.
Hi Bob,
Are you positive that the parachute is really deploying before apogee? This is something we have never seen in any testing. We spent a great deal of time working on that part of the code, and if anything it should be biased to being a fraction of a second after apogee, since the altitude is read at regular intervals and so the velocity would have to be zero or negative for a complete interval before the software could detect it. The algorithm is not predictive, because there's very limited memory in these low cost microcontroller boards.

It's possible that the pressure ports may need to be larger due to some unforeseen influence that we never encountered. Just as a guess, perhaps the pressure drops in the part of the rocket where you have the altimeter due to compression of the bottles during launch and the subsequent relaxation of the bottles as the rocket decelerates? This is just a speculation.

Is it possible that from your vantage point on the ground it simply looks to you like the rocket is still going up, but in reality it has stalled at apogee and you are seeing some sort of optical illusion that makes it look at though it is climbing?

The only way to know for sure would be to fly and onboard camera and see if you can hear the servo move before or after the rocket starts coming down.

We've never had one deploy early and we have probably over 100 videos of the altimeter during testing and 100 more videos of the altimeter being used for development of our Radial and Hybrid Deploy techniques. But anything is possible. We just don't know what you could be seeing.
Just another question on the pressure holes. Where do you position them with regard to the pressure sensor?

cheers

Bob



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Blenderite
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Re: LaunchPad AlTImeter Technical Support Forum

Post by Blenderite » Mon Jan 05, 2015 7:23 pm

U.S. Water Rockets wrote:
DogLover wrote:No it was a epic fail during soldering.
Thanks for being honest about that;-)

Have you been able to launch it yet? You're really going to love how simple it is to use.
I am super busy with work so I have not had much time recently. However I have gotten some of the necessary materials and am working on some spliced pairs.


-Blenderite

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"Get it right, then go for GREATNESS!"

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U.S. Water Rockets
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Re: Static pressure holes

Post by U.S. Water Rockets » Mon Jan 05, 2015 10:32 pm

blannoy wrote: Just another question on the pressure holes. Where do you position them with regard to the pressure sensor?
Bob,

As long as the holes are in the same "compartment" as the sensor, it will be ok. The only caution is not to make a huge oversize compartment. Try and keep the space you place the altimeter relatively small, or else you will need to add a lot of holes or make the holes larger. The pressure inside the compartment has to be the same as the outside air as the rocket flies up. If you make a huge 2 liter compartment and put one 2mm hole in it, the pressure inside the compartment will lag behind the exterior pressure because a large compartment will need to move a lot of air in or out of that tiny hole to make the pressure equal inside and out.

Keep in mind that even with a really poor vent port design, the deploy and everything will still work, but you might get a lower altitude flight reading they you actually flew because the air pressure didn't keep up with the change in altitude.



blannoy
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Servochron firmware on Altimeter

Post by blannoy » Mon Jan 26, 2015 3:19 pm

Hi,

I had two crashes yesterday with a modified design of the compartment. I redesigned it to be more rigid to avoid pressure variations. I made several holes and tested it with a "kiss". The servo turned nicely.
Unfortunately, on the two launches the rocket crashed into the ground. Without any additional clues to go on (no onboard camera or video footage) I've lost confidence that this might work. I will try again with some bigger holes but the compartment isn't big (.5 liters).

Therefore, I was thinking of reverting to the servochron. I saw this is the same board but the servo needs to be on another pin. I was wondering if it would be feasible to adapt the servochron firmware so that it runs on the altimeter without having to resolder the existing connections?

cheers

Bob



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U.S. Water Rockets
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Re: Servochron firmware on Altimeter

Post by U.S. Water Rockets » Mon Jan 26, 2015 8:41 pm

blannoy wrote:Hi,

I had two crashes yesterday with a modified design of the compartment. I redesigned it to be more rigid to avoid pressure variations. I made several holes and tested it with a "kiss". The servo turned nicely.
Unfortunately, on the two launches the rocket crashed into the ground. Without any additional clues to go on (no onboard camera or video footage) I've lost confidence that this might work. I will try again with some bigger holes but the compartment isn't big (.5 liters).

Therefore, I was thinking of reverting to the servochron. I saw this is the same board but the servo needs to be on another pin. I was wondering if it would be feasible to adapt the servochron firmware so that it runs on the altimeter without having to resolder the existing connections?

cheers

Bob

Hi Bob,

Sorry you are struggling with the crashes. From our experience and the experience of others, it seems that your problem really isn't the altimeter or the compartment. We've seen people with absolutely terrible compartment designs that have had success with the altimeter. That leaves us with other possible causes:

Is launch getting detected? Upon landing (even after a crash) is there a new altitude recorded? If it's beeping out 323 feet when it lands but was beeping 336 on the previous flight, then it detected launch for the flight that just happened. If the rocket is beeping the same altitude after the second flight then it didn't detect launch or went exactly the same height (not likely). The same number means no launch detected, so we have to look at that problem first:
1) Is the rocket going high enough to detect a launch? You have to over about 20 meters high to detect a real launch.
2) Is the rocket going fast enough to detect a launch? The rocket should be going faster than 15 meters per second to detect a launch. If you're using a low pressure and a tiny nozzle or a huge heavy rocket, it might not get going fast enough.
3) The last possibility is the vent holes, but this is not likely from what you described.

Is the parachute getting activated and just doesn't work? If we can tell that launch was detected, then the problem is not with the rocket speed or altitude, and probably not with the air holes. So:
1) Is there something wrong with the deploy system itself? Some people like to use those old fashioned "trap door" deploy systems, because there are so many tutorials out there for them. These systems depend on several moving parts and careful assembly to insure reliability. Sharp corners or edges can lead to snagging of the mechanism, among many other problems. Sometimes the problem doesn't manifest itself until the rocket actually flies. Such as the same system you test on the pad 10 times works great, but when you fly it the g-load shifts something or wedges something and in the air it fails.
2) Does the system take a long time to deploy the parachute? If you have a deploy system that works slowly, does it simply not get the chute open fast enough before the ground rushes up to greet the rocket? By the same token, if you accidentally programmed a deploy delay into the Altimeter, the rocket may crash while the delay is counting down after apogee. You should check for this condition or program a new delay that is 0 or 1 second to insure the deploy is happing quickly.
3) Has the chute deployed but failed to inflate or just tangled? This condition happens when the parachute does come out but gets sucked into the wake of the rocket. If you have a short string on the parachute, it may be getting sucked against the body of the rocket, or in the vacuum right behind the rocket. In these places, the parachute often will not catch enough air to deploy.

We're going to have to work on these other issues and see if we can't figure out what is going on.

Also, to answer your question, it's not really feasible to try and add the servochron features to the Altimeter. It might be possible if we relocated some of the signals that go to the pressure sensor to other pins, but we picked the arrangement that it uses so that people could just solder the sensor PCB directly to the pins. If we rearrange the signals to allow for both functions, then people would need to manually jumper the signals to the sensor board with individual wires, which is a lot less neat and tidy. People would have a lot more issues with the build if we did it like that.

Give the suggestions a try and hopefully we can turn up something.



blannoy
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Re: Servochron firmware on Altimeter

Post by blannoy » Tue Jan 27, 2015 8:24 am

U.S. Water Rockets wrote: Hi Bob,

Sorry you are struggling with the crashes. From our experience and the experience of others, it seems that your problem really isn't the altimeter or the compartment. We've seen people with absolutely terrible compartment designs that have had success with the altimeter. That leaves us with other possible causes:

Is launch getting detected? Upon landing (even after a crash) is there a new altitude recorded? If it's beeping out 323 feet when it lands but was beeping 336 on the previous flight, then it detected launch for the flight that just happened. If the rocket is beeping the same altitude after the second flight then it didn't detect launch or went exactly the same height (not likely). The same number means no launch detected, so we have to look at that problem first:
1) Is the rocket going high enough to detect a launch? You have to over about 20 meters high to detect a real launch.
2) Is the rocket going fast enough to detect a launch? The rocket should be going faster than 15 meters per second to detect a launch. If you're using a low pressure and a tiny nozzle or a huge heavy rocket, it might not get going fast enough.
3) The last possibility is the vent holes, but this is not likely from what you described.

Is the parachute getting activated and just doesn't work? If we can tell that launch was detected, then the problem is not with the rocket speed or altitude, and probably not with the air holes. So:
1) Is there something wrong with the deploy system itself? Some people like to use those old fashioned "trap door" deploy systems, because there are so many tutorials out there for them. These systems depend on several moving parts and careful assembly to insure reliability. Sharp corners or edges can lead to snagging of the mechanism, among many other problems. Sometimes the problem doesn't manifest itself until the rocket actually flies. Such as the same system you test on the pad 10 times works great, but when you fly it the g-load shifts something or wedges something and in the air it fails.
2) Does the system take a long time to deploy the parachute? If you have a deploy system that works slowly, does it simply not get the chute open fast enough before the ground rushes up to greet the rocket? By the same token, if you accidentally programmed a deploy delay into the Altimeter, the rocket may crash while the delay is counting down after apogee. You should check for this condition or program a new delay that is 0 or 1 second to insure the deploy is happing quickly.
3) Has the chute deployed but failed to inflate or just tangled? This condition happens when the parachute does come out but gets sucked into the wake of the rocket. If you have a short string on the parachute, it may be getting sucked against the body of the rocket, or in the vacuum right behind the rocket. In these places, the parachute often will not catch enough air to deploy.

We're going to have to work on these other issues and see if we can't figure out what is going on.

Also, to answer your question, it's not really feasible to try and add the servochron features to the Altimeter. It might be possible if we relocated some of the signals that go to the pressure sensor to other pins, but we picked the arrangement that it uses so that people could just solder the sensor PCB directly to the pins. If we rearrange the signals to allow for both functions, then people would need to manually jumper the signals to the sensor board with individual wires, which is a lot less neat and tidy. People would have a lot more issues with the build if we did it like that.

Give the suggestions a try and hopefully we can turn up something.
Hi,

OK I'll try some more launches. The parachute did not deploy on both occasions, but I didn't pay attention to the reported altitude. I think speed and height are OK as well since I had two successful launches around Christmas.

With regard to the firmware, I didn't mean to have a single firmware for servochron and altimeter, but an alternative firmware of servochron that I could flash onto my altimeter board. This would use additional pins for the breaking wire but keep the servo on the same pin as in the altimeter. I started toying with the Energia msp430 editor (an Arduino like system: http://energia.nu) and achieved a fixed timing and turning servo on a press of a the button on my current altimeter in a short time due to the availability of libraries. I would need more time to get something similar as your servochron firmware. It would be easier to have your firmware but slightly modified so I still have the choice (by flashing another firmware) without having to resolder things.

A question related to this, is there a possibility to keep track of the pressure variations of a flight (in flash memory) and report that in some way that I can plot it? (ok I'm asking a lot here ;) )

Cheers

Bob



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U.S. Water Rockets
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Re: Servochron firmware on Altimeter

Post by U.S. Water Rockets » Thu Jan 29, 2015 12:15 am

blannoy wrote:With regard to the firmware, I didn't mean to have a single firmware for servochron and altimeter, but an alternative firmware of servochron that I could flash onto my altimeter board. This would use additional pins for the breaking wire but keep the servo on the same pin as in the altimeter.
Allright. That makes more sense, if you wanted to change the function by loading different firmware. There is a downside to doing this, however. Now there will be different firmware for the ServoChron function that would be needed for two incompatible hardware configurations. We're trying to reach people with these designs that are not familiar with electronics or microcontrollers, so we have kept the variations to a minimum. If we throw a new timer firmware out there, people might load it into the original ServoChron boards they made, and it won't work, then they will be upset with us. We want to minimize the amount of things we put out that could lead to confusion.
A question related to this, is there a possibility to keep track of the pressure variations of a flight (in flash memory) and report that in some way that I can plot it? (ok I'm asking a lot
This is how a logging altimeter would work, but that's a huge undertaking, and there's not enough time in the day for our current projects. You know how that goes...



blannoy
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Re: Servochron firmware on Altimeter

Post by blannoy » Thu Jan 29, 2015 3:49 am

U.S. Water Rockets wrote:
blannoy wrote:With regard to the firmware, I didn't mean to have a single firmware for servochron and altimeter, but an alternative firmware of servochron that I could flash onto my altimeter board. This would use additional pins for the breaking wire but keep the servo on the same pin as in the altimeter.
Allright. That makes more sense, if you wanted to change the function by loading different firmware. There is a downside to doing this, however. Now there will be different firmware for the ServoChron function that would be needed for two incompatible hardware configurations. We're trying to reach people with these designs that are not familiar with electronics or microcontrollers, so we have kept the variations to a minimum. If we throw a new timer firmware out there, people might load it into the original ServoChron boards they made, and it won't work, then they will be upset with us. We want to minimize the amount of things we put out that could lead to confusion.
A question related to this, is there a possibility to keep track of the pressure variations of a flight (in flash memory) and report that in some way that I can plot it? (ok I'm asking a lot
This is how a logging altimeter would work, but that's a huge undertaking, and there's not enough time in the day for our current projects. You know how that goes...
Ok I understand. I'll try to develop my own timer on the current setup.

With regard to the logging altimeter, I could take a shot at that. The problem is that I don't have any electronics experience but I do know programming.
As I mentioned, I'm using the http://energia.nu editor which is compatible with Arduino type-programming. I took the arduino code from the sparkfun website (https://www.sparkfun.com/products/11084) but I'm not able to read out the sensor. It hangs when trying to communicate with the sensor, so I'm stuck. Can I get some example code to read out the pressure sensor?

cheers

Bob



blannoy
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Re: Servochron firmware on Altimeter

Post by blannoy » Sun Feb 01, 2015 2:47 pm

blannoy wrote:
U.S. Water Rockets wrote:
blannoy wrote:With regard to the firmware, I didn't mean to have a single firmware for servochron and altimeter, but an alternative firmware of servochron that I could flash onto my altimeter board. This would use additional pins for the breaking wire but keep the servo on the same pin as in the altimeter.
Allright. That makes more sense, if you wanted to change the function by loading different firmware. There is a downside to doing this, however. Now there will be different firmware for the ServoChron function that would be needed for two incompatible hardware configurations. We're trying to reach people with these designs that are not familiar with electronics or microcontrollers, so we have kept the variations to a minimum. If we throw a new timer firmware out there, people might load it into the original ServoChron boards they made, and it won't work, then they will be upset with us. We want to minimize the amount of things we put out that could lead to confusion.
A question related to this, is there a possibility to keep track of the pressure variations of a flight (in flash memory) and report that in some way that I can plot it? (ok I'm asking a lot
This is how a logging altimeter would work, but that's a huge undertaking, and there's not enough time in the day for our current projects. You know how that goes...
Ok I understand. I'll try to develop my own timer on the current setup.

With regard to the logging altimeter, I could take a shot at that. The problem is that I don't have any electronics experience but I do know programming.
As I mentioned, I'm using the http://energia.nu editor which is compatible with Arduino type-programming. I took the arduino code from the sparkfun website (https://www.sparkfun.com/products/11084) but I'm not able to read out the sensor. It hangs when trying to communicate with the sensor, so I'm stuck. Can I get some example code to read out the pressure sensor?

cheers

Bob
Just to let you know that I can read out the sensor. I'll try to log to flash during a few seconds. Just to be on the safe side, I'll use a breaking wire and timer.

Bob



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Re: LaunchPad AlTImeter Technical Support Forum

Post by Chip92706 » Sat Feb 14, 2015 11:23 am

I just started testing the altimeter and the problem that I found is that my servo motor won't deploy.



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U.S. Water Rockets
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Re: LaunchPad AlTImeter Technical Support Forum

Post by U.S. Water Rockets » Sat Feb 14, 2015 5:43 pm

Chip92706 wrote:I just started testing the altimeter and the problem that I found is that my servo motor won't deploy.
Are you using a servo motor that you just happened to have laying around, or was it one that you ordered from the parts list?

If you use any old servo, it might not work because we're using a LiPo battery that puts out about 4.2V when fully charged, and drops down from there as it is depleted. Many servos are designed to run off 5-6V and the LiPo voltage is too low for the servo to operate. That's why we called out a specific model in the instructions, since the one we listed is dirt cheap and it is confirmed to be working at the lower voltage.

On the other hand, the servo could also be perfectly compatible with the battery voltage but the servo is simply just defective. At the price they sell them for, there are bound to be occasional failures. We always buy 3-5 at a time so that we have spares in case one is bad or we break one. Sometimes water gest inside our rocket when it splashes down in the lake and that can ruin the servos, so we have plenty of spares on hand.

If you have a spare, then try that. There are almost no other ways it can fail to deploy.



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Blenderite
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Re: LaunchPad AlTImeter Technical Support Forum

Post by Blenderite » Sat Feb 14, 2015 9:00 pm

There is also a chance that the wires are soldered incorrectly. That happened to me and I had the same results! I know there are some servos that have a red and orange wire, which can be difficult to tell apart on a quick glance.


-Blenderite

Check out my YouTube channel: https://www.youtube.com/c/Blenderite

"Get it right, then go for GREATNESS!"

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tonyvs
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Re: LaunchPad AlTImeter Technical Support Forum

Post by tonyvs » Sat Feb 21, 2015 3:07 pm

Hello everyone.

I am new to this forum although I have been hooked on Us Water rockets since last auturm. My son and I (he is only 7 so I've done all the work!!) have constructed many test rockets and have now successfully launched a 10 litre rocket although with no electronics yet. My guess is that we reached a height of 100 to 150 metres.

I have purchased all the components to build the LaunchPad Altimeter, the MSP-EXP430G2 circuit board, Altimeter, buzzer, and server motor, I have put them all together following the youtube video, but I'm getting the same problem as Blenderite in his post in April of 2012, a constant buzzing noise. I would describe the buzzing as a harsh or unusual sound.

I have checked and double checked that there is no short and that the wiring is correct. I have changed the microcontroller chip and and reprogrammed the firmware making sure it is the one for the altimeter. [LPAlt_V100.FET430prj]. This gives a PASS message and seems all OK.

I am in Spain and have no one to ask for help here. I'm an IT Administrator and have no electronics knowledge. Everything I do is follow the instructions on the US Water Rockets web.

Could anyone please help me? I could send pictures or videos if necesarry.

Thanks again.



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U.S. Water Rockets
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Re: LaunchPad AlTImeter Technical Support Forum

Post by U.S. Water Rockets » Sat Feb 21, 2015 6:34 pm

tonyvs wrote:Hello everyone.

I am new to this forum although I have been hooked on Us Water rockets since last auturm. My son and I (he is only 7 so I've done all the work!!) have constructed many test rockets and have now successfully launched a 10 litre rocket although with no electronics yet. My guess is that we reached a height of 100 to 150 metres.

I have purchased all the components to build the LaunchPad Altimeter, the MSP-EXP430G2 circuit board, Altimeter, buzzer, and server motor, I have put them all together following the youtube video, but I'm getting the same problem as Blenderite in his post in April of 2012, a constant buzzing noise. I would describe the buzzing as a harsh or unusual sound.

I have checked and double checked that there is no short and that the wiring is correct. I have changed the microcontroller chip and and reprogrammed the firmware making sure it is the one for the altimeter. [LPAlt_V100.FET430prj]. This gives a PASS message and seems all OK.

I am in Spain and have no one to ask for help here. I'm an IT Administrator and have no electronics knowledge. Everything I do is follow the instructions on the US Water Rockets web.

Could anyone please help me? I could send pictures or videos if necesarry.

Thanks again.
Hi tonyvs!
Thanks for telling us about your story and giving us such positive feedback! Sorry to hear you have had trouble with the altimeter build. We will try and help out!

The best thing you could do to help is take some clear pictures of the top and bottom of the board, showing the connections you made and the wiring of the servo. The servo wire colors are of interest to us as well.

Other than the buzzing, a description of any beeping the speaker is doing or flashing of the LED lights would also help us track down any problems you have had.

Upload what you can and we will take a look at it.



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Re: LaunchPad AlTImeter Technical Support Forum

Post by tonyvs » Tue Feb 24, 2015 3:12 pm

Hello there!

Here are a few pictures of my launch pad and a video where you can hear the sound and see that all the lights are lit. The mode button has no effect, the reset button does stop the sound and switch off led1 and led 2 whilst I keep it pressed.

The result is the same if I don't connect the servo motor. The red, white and black buttons go to the orange, red and brown wires respectively on the servo motor.

Thank you again for your help.

Let me know if you need anymore information and/or photos.
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