Tele Mega Trouble

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Ric

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I'm having a little trouble using a Tele Mega for a 2 stage rocket. Using the altimeter configuration I set main chute opening for 750'. I set Pyro D as a backup main at 499'. Pyro A was apogee backup and Pyro C was sustainer ignition. So Pyro D fired on the way up rather than down and ended the flight rather quickly. I have solved that issue but the flight graph revealed other issues which I don't understand. #1 Why didn't Pyro A fire? #2 Pyro C seems to indicate that it fired (slight voltage dip) but it fact it did not. Why? #3 Pyro D voltage shows a steep decline. Why? Any insights would be appreciated.
 

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kbRocket

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Disclaimer: I bought a Tele Mega to use in two stage next year, but I haven't programmed it or tested it, so I don't have the expertise to definitively answer your questions. I do have experience with other Altus Metrum products and am a heavy use of them.

Despite my lack of specific Tele Mega knowledge, I can see some reasons for igniter D to fire on the way up and none of the other igniters to fire, at least in the time frame shown.

Igniter D is set to fire after motor 1 and less than 499 feet. From the accelerometer data it looks like motor 1 was done about 1.1 seconds (accel dropped to 0) and the height was < 499 feet even though the rocket was still moving upward. As a backup main probably set it to fire 2 seconds after state goes to main.

Pyro channel C will fire 3 seconds after both motor 1 and after boost state. The time record shown only extends 2.2 seconds total. I cannot explain why igniter C is printed at about 1.95 seconds, or the minor voltage dip, but I don't think the computer attempted to fire the igniter. It shouldn't have attempted until the time of about 4.35 seconds, 3 seconds after boost ended.

Pyro channel A will fire 2 seconds after you change to the drogue state. In the time record provided you never entered drogue state, just coast. This makes sense if you look at height. Other than a brief low spike as igniter D fires (which is typically be caused by a charge pressure spike) the height basically continues going up for the whole time record you have shown, so I don't expect Drogue state yet. The speed is also 140 ft/second at the end of the time record, implying still going up. The state machine is probably relying upon the Kalman filter output to detect apogee. I suspect that firing the redundant main on the way up may cause some confusion in the filter and state transition.

What happens in extended time?
Can you post the whole flight record?
 

Ric

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Here is the full log. Thanks for your insights. Lots to think about.
 

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kbRocket

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Could you upload the .eeprom file?

I would like to examine some other signals such as the battery voltage and tilt.
I am wondering if you have a poor or intermittent battery connection could explain the slight sag in Igniter C voltage at 2.0 seconds.
I am also trying to figure out why the recording ends just before 5 seconds when the altitude is allegedly near 600 feet, we are still in coast phase, and velocity negative but not zero. Seems like the unit quit before the rocket was on the ground which makes me suspect battery.

The person who programs the Altus Metrum once told me that setting a TeleMetrum to use redundant apogee activates a different part of the code. I expected to see the main fire exactly 2 seconds after drogue and it was later. However in the code the main fires as a redundant apogee 2 seconds after apogee. It is not reflected in the state machine

This has me thinking about the exactly 3 seconds between "igniter C" and the end of the recording. Perhaps the "igniter C" tag tells igniter C to do it's thing, which is to delay 3 seconds and fire. Perhaps igniter C has a short circuit and with a 0.1 second firing time this drags down the circuit voltage causing everything to stop.
 

OverTheTop

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Do I recall that timers set to trigger by flight phase are triggered at the start of the phase, not the end? Check the documentation. I remember something peculiar with that area of operation

I flew a TeleMega successfully last year on an O-M project. Performed flawlessly except went dark at apogee (37500') so I still have yet to recover the sustainer.
 

JimJarvis50

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I haven't looked at your specific issues, but I fly EasyMega's frequently, including three stage projects to high altitude. I have never used the "state" conditions. I don't believe they are necessary and it seems to me that just leaves decisions on fight events to whomever programmed what the states mean. Just my $0,02. I could be wrong on their value, but if I can do what I do without them, then you can too, and I think you would find the programming more straightforward.

Jim

PS. OTT, that problem was fixed with a not-all-that-recent firmware update. I believe the problerm was a resetting of the timer after a burnout.
 

OverTheTop

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PS. OTT, that problem was fixed with a not-all-that-recent firmware update. I believe the problerm was a resetting of the timer after a burnout.
Is that the telemetry going dark problem, related to a timer? I have previously flown it dozens of times without issue.
 

JimJarvis50

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Is that the telemetry going dark problem, related to a timer? I have previously flown it dozens of times without issue.
The problem I'm referring to, which is what I thought you were referring to, is that the timer would reset after a burnout. You would think you were setting the timer to be the time from launch, and then it would reset. It wasn't stated to be that way in the documentation. Kip ran into this, and his apogee event was late as a result. This got fixed, and I believe you can now set the timer to either reset or to be from launch. I'd have to check the details - it's been a while since I looked at this. But I recommended that the timer be from launch at the time this was being addressed.

Jim
 

Ric

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Could you upload the .eeprom file?

I would like to examine some other signals such as the battery voltage and tilt.
I am wondering if you have a poor or intermittent battery connection could explain the slight sag in Igniter C voltage at 2.0 seconds.
I am also trying to figure out why the recording ends just before 5 seconds when the altitude is allegedly near 600 feet, we are still in coast phase, and velocity negative but not zero. Seems like the unit quit before the rocket was on the ground which makes me suspect battery.

The person who programs the Altus Metrum once told me that setting a TeleMetrum to use redundant apogee activates a different part of the code. I expected to see the main fire exactly 2 seconds after drogue and it was later. However in the code the main fires as a redundant apogee 2 seconds after apogee. It is not reflected in the state machine

This has me thinking about the exactly 3 seconds between "igniter C" and the end of the recording. Perhaps the "igniter C" tag tells igniter C to do it's thing, which is to delay 3 seconds and fire. Perhaps igniter C has a short circuit and with a 0.1 second firing time this drags down the circuit voltage causing everything to stop.
Could you upload the .eeprom file?

I would like to examine some other signals such as the battery voltage and tilt.
I am wondering if you have a poor or intermittent battery connection could explain the slight sag in Igniter C voltage at 2.0 seconds.
I am also trying to figure out why the recording ends just before 5 seconds when the altitude is allegedly near 600 feet, we are still in coast phase, and velocity negative but not zero. Seems like the unit quit before the rocket was on the ground which makes me suspect battery.

The person who programs the Altus Metrum once told me that setting a TeleMetrum to use redundant apogee activates a different part of the code. I expected to see the main fire exactly 2 seconds after drogue and it was later. However in the code the main fires as a redundant apogee 2 seconds after apogee. It is not reflected in the state machine

This has me thinking about the exactly 3 seconds between "igniter C" and the end of the recording. Perhaps the "igniter C" tag tells igniter C to do it's thing, which is to delay 3 seconds and fire. Perhaps igniter C has a short circuit and with a 0.1 second firing time this drags down the circuit voltage causing everything to stop.
What is the eeprom file and where do i find
Could you upload the .eeprom file?

I would like to examine some other signals such as the battery voltage and tilt.
I am wondering if you have a poor or intermittent battery connection could explain the slight sag in Igniter C voltage at 2.0 seconds.
I am also trying to figure out why the recording ends just before 5 seconds when the altitude is allegedly near 600 feet, we are still in coast phase, and velocity negative but not zero. Seems like the unit quit before the rocket was on the ground which makes me suspect battery.

The person who programs the Altus Metrum once told me that setting a TeleMetrum to use redundant apogee activates a different part of the code. I expected to see the main fire exactly 2 seconds after drogue and it was later. However in the code the main fires as a redundant apogee 2 seconds after apogee. It is not reflected in the state machine

This has me thinking about the exactly 3 seconds between "igniter C" and the end of the recording. Perhaps the "igniter C" tag tells igniter C to do it's thing, which is to delay 3 seconds and fire. Perhaps igniter C has a short circuit and with a 0.1 second firing time this drags down the circuit voltage causing everything to stop.
What is the eeprom file and where do I find it? I am away from home for the next several weeks and don't have access to the altimeter. This is all very new to me so I very much appreciate your interest/help.
BTW I use two 9 volt batteries for pyro. They are located physically opposite to each other in an effort to eliminate transient disconnects caused by g forces.
 

kbRocket

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If you click on Save Flight Data in the AltOS interface with your TeleMega connected, you get some checkboxes allowing you to download, graph, and delete the data.
saveflight.png
For now just download/graph is fine, but eventually you will need to delete the data off your TeleMega because it will get full with lots of flights.

Once you have downloaded the data you can then graph it without the need to be connected to your TeleMega and send the file to others who can help understand it.

On a windows computer the file ends up in your user data. For me that is this folder: C:\Users\xxxMyUserNamexxx\Documents\TeleMetrum
where the xxxMyUserNamexxx should be your computer user name. If you go into C:\Users you will probably have a short list of user names to choose from.
 

Ric

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If you click on Save Flight Data in the AltOS interface with your TeleMega connected, you get some checkboxes allowing you to download, graph, and delete the data.
View attachment 426285
For now just download/graph is fine, but eventually you will need to delete the data off your TeleMega because it will get full with lots of flights.

Once you have downloaded the data you can then graph it without the need to be connected to your TeleMega and send the file to others who can help understand it.

On a windows computer the file ends up in your user data. For me that is this folder: C:\Users\xxxMyUserNamexxx\Documents\TeleMetrum
where the xxxMyUserNamexxx should be your computer user name. If you go into C:\Users you will probably have a short list of user names to choose from.
 

Ric

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Can't upload .eeprom files to rocketry forum. Any ideas?
 

keithp

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I'm having a little trouble using a Tele Mega for a 2 stage rocket. Using the altimeter configuration I set main chute opening for 750'. I set Pyro D as a backup main at 499'. Pyro A was apogee backup and Pyro C was sustainer ignition. So Pyro D fired on the way up rather than down and ended the flight rather quickly. I have solved that issue but the flight graph revealed other issues which I don't understand. #1 Why didn't Pyro A fire? #2 Pyro C seems to indicate that it fired (slight voltage dip) but it fact it did not. Why? #3 Pyro D voltage shows a steep decline. Why? Any insights would be appreciated.
We know that the current pyro configuration mechanism is difficult to understand and program correctly and encourage people to reach out to us with questions.

Let's step through these issues one at a time.

Pyro D fired during ascent because it was programmed to fire after the first motor burned as soon as the rocket was below 499 feet. That turned out to be during ascent.

Pyro A didn't fire either because the altimeter never reached Drogue state (it didn't detect a solid apogee), or because there wasn't any time between Drogue and Main states (this happens if Drogue occurs below the Main altitude).

Pyro C didn't fire -- you're seeing the time at which it was inhibited, presumably due to the tilt limit being exceeded. This is mis-leading and I should fix it so that it doesn't appear like this in the log.

Pyro D shows a steep voltage drop because the igniter went 'open' which makes the pyro voltage drop. That's how we tell if an igniter is connected at all.

Let's figure out how to configure things to do what you wanted.

  • Apogee Backup (Pyro A): Flight State after: Drogue. Delay after other conditions: 1s.
  • Main Backup (Pyro D): Flight State after Drogue: Height above pad less than: 499 ft.
  • Sustainer Ignition (Pyro C): After motor number: 1 Angle from vertical less than: 20. Delay after other conditions: 3s.
I recommend using 'Flight State After: Drogue' to determine when the rocket is descending because that takes all of the apogee-detection logic into account, including any programmed apogee lockout and built-in logic that avoids false apogee determination due to mach transition effects.

'After motor number: 1' is the almost the same as 'Flight state after: Boost' as the flight computer counts motor burnouts based on when the state transitions from Boost to Fast/Coast. I prefer to use it as it extends to more than two stages nicely.

During the 'Delay after other conditions' period, which starts when all of the other conditions are simultaneously true, TeleMega continuously tests those conditions and if they ever become false, then that igniter is disabled for the flight. In the case of this flight, that means TeleMega is monitoring the tilt angle for the three seconds after the first motor burnout; if the rocket ever tilts too far, that igniter will not fire.

I'd love a copy of the .eeprom file if you can send it to me, and if you have any further questions, please don't hesitate to reach out to us. Helping people fly safely and successfully is the best part of this job.
 

kbRocket

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I did some analysis and plotting of signals in the .xlsx attached above. Keith's analysis of signals look correct based on the data.

Pyro A did not fire because we did not reach drogue state. In the entire file we only have boost and coast states. Then there is no data after 4.96 seconds. It isn't clear why the recording stopped at 4.96 seconds.

I thought we might see voltages dropping close to the end of the recording indicating that we had poor battery contact and were draining power from an onboard capacitor, but this isn't the case. Battery voltage is solid until the end.

voltage.png

Pyro C should have been inhibited due to tilt because tilt was much larger than 20 degrees:
tilt.png



The reason why the recording suddenly stopped at 4.96 seconds during coast phase and while well off the ground is the biggest mystery.

height.png
 

Ric

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I did some analysis and plotting of signals in the .xlsx attached above. Keith's analysis of signals look correct based on the data.

Pyro A did not fire because we did not reach drogue state. In the entire file we only have boost and coast states. Then there is no data after 4.96 seconds. It isn't clear why the recording stopped at 4.96 seconds.

I thought we might see voltages dropping close to the end of the recording indicating that we had poor battery contact and were draining power from an onboard capacitor, but this isn't the case. Battery voltage is solid until the end.

View attachment 426421
Pyro C should have been inhibited due to tilt because tilt was much larger than 20 degrees:
View attachment 426424


The reason why the recording suddenly stopped at 4.96 seconds during coast phase and while well off the ground is the biggest mystery.

View attachment 426426
Thanks Kelly. BTW you saw this flight at Brothers.
 

Ric

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We know that the current pyro configuration mechanism is difficult to understand and program correctly and encourage people to reach out to us with questions.

Let's step through these issues one at a time.

Pyro D fired during ascent because it was programmed to fire after the first motor burned as soon as the rocket was below 499 feet. That turned out to be during ascent.

Pyro A didn't fire either because the altimeter never reached Drogue state (it didn't detect a solid apogee), or because there wasn't any time between Drogue and Main states (this happens if Drogue occurs below the Main altitude).

Pyro C didn't fire -- you're seeing the time at which it was inhibited, presumably due to the tilt limit being exceeded. This is mis-leading and I should fix it so that it doesn't appear like this in the log.

Pyro D shows a steep voltage drop because the igniter went 'open' which makes the pyro voltage drop. That's how we tell if an igniter is connected at all.

Let's figure out how to configure things to do what you wanted.

  • Apogee Backup (Pyro A): Flight State after: Drogue. Delay after other conditions: 1s.
  • Main Backup (Pyro D): Flight State after Drogue: Height above pad less than: 499 ft.
  • Sustainer Ignition (Pyro C): After motor number: 1 Angle from vertical less than: 20. Delay after other conditions: 3s.
I recommend using 'Flight State After: Drogue' to determine when the rocket is descending because that takes all of the apogee-detection logic into account, including any programmed apogee lockout and built-in logic that avoids false apogee determination due to mach transition effects.

'After motor number: 1' is the almost the same as 'Flight state after: Boost' as the flight computer counts motor burnouts based on when the state transitions from Boost to Fast/Coast. I prefer to use it as it extends to more than two stages nicely.

During the 'Delay after other conditions' period, which starts when all of the other conditions are simultaneously true, TeleMega continuously tests those conditions and if they ever become false, then that igniter is disabled for the flight. In the case of this flight, that means TeleMega is monitoring the tilt angle for the three seconds after the first motor burnout; if the rocket ever tilts too far, that igniter will not fire.

I'd love a copy of the .eeprom file if you can send it to me, and if you have any further questions, please don't hesitate to reach out to us. Helping people fly safely and successfully is the best part of this job.
 

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kbRocket

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Ric

I don't see anything additional in the .eeprom file. This still leaves the mystery of why the recording stopped at 4.96 seconds without a voltage sag and the rocket off the ground in coast phase.

Joey and I are motivated to figure out the mysteries of TeleMega and EasyTimer programming because we both plan on starting multi-stage rockets in the near future. We are trying to learn and help and gain experience.

It was a sad flight, but at least everything was found and damage was minimal/repairable. I hope to see you back out in the sage again soon.

kb
 

Ric

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Ric

I don't see anything additional in the .eeprom file. This still leaves the mystery of why the recording stopped at 4.96 seconds without a voltage sag and the rocket off the ground in coast phase.

Joey and I are motivated to figure out the mysteries of TeleMega and EasyTimer programming because we both plan on starting multi-stage rockets in the near future. We are trying to learn and help and gain experience.

It was a sad flight, but at least everything was found and damage was minimal/repairable. I hope to see you back out in the sage again soon.

kb
Not sad by any means. I expect broken rockets as I learn.
 
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