Stratologger SL100 Issues

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TachoLycos

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Launched a new rocket yesterday. 65", 4" body tube on a I284WT. Great flight on the way up. Then the problems started.

No apogee event. No main event. 2 stratologger sl100 altimeters. One used as primary and set at apogee +1 for drogue and 600 feet for main. Redundant set at apogee +2/500 feet. Both altimeters beeping on the ground before and after flight. None of the 4 Jtek e-matches burned. They worked the day before for multiple ejection tests. New batteries for flight. ~9.5V on both batteries. Continuity on all the wires checked after the flight. Downloaded the flight afterwards. Primary altimeter showed the whole flight to 2400 feet and showed events at apogee +1 and at 600 feet. Redundant altimeter showed a power loss and did not collect good data(showed an apogee on the graph of 65000 feet lol). <<reason for redundancy.

Both altimeters have been used for 10-15 flights including a flight to 10,000 feet a couple months ago.

Any ideas on what went wrong with the primary altimeter? Going to replace both of these, recommendations for replacement?

Thanks,
Chris

Picture from flight attached.

image.jpg
 
TachoLycos said:
Launched a new rocket yesterday. 65", 4" body tube on a I284WT. Great flight on the way up. Then the problems started.

No apogee event. No main event. 2 stratologger sl100 altimeters. One used as primary and set at apogee +1 for drogue and 600 feet for main. Redundant set at apogee +2/500 feet. Both altimeters beeping on the ground before and after flight. None of the 4 Jtek e-matches burned. They worked the day before for multiple ejection tests. New batteries for flight. ~9.5V on both batteries. Continuity on all the wires checked after the flight. Downloaded the flight afterwards. Primary altimeter showed the whole flight to 2400 feet and showed events at apogee +1 and at 600 feet. Redundant altimeter showed a power loss and did not collect good data(showed an apogee on the graph of 65000 feet lol). <<reason for redundancy.

Both altimeters have been used for 10-15 flights including a flight to 10,000 feet a couple months ago.

Any ideas on what went wrong with the primary altimeter? Going to replace both of these, recommendations for replacement?

Thanks,
Chris

I would make sure battery connections are intact and no way loosened by the G forces at launch.
I always mount my batteries upside down so that under acceleration, the battery is pushed against the terminals.
I use new alkaline batteries at every launch and discard at the end of the day even if only used once.
I would need to see pictures of your av layout to render a better opinion.

I have had some issues in the past with my Perfectflite miniAltWDs when there was accidental pressurization of the av bay, but the 1st charge always fired but the damage to the altimeter would prevent the main to deploy.
Any large L2 or every L3 rocket I now use a Missleworks WRC2 wireless controller as a backup for the main. I made a universal mount that installs inside any of my 6" or larger nose cones.

All of my av bays have 2 altimeters where the 2 main and 2 apogee igniters. Each pair is in the same charge cup. It is unlikely the powder will fail the reason why I do not use 4 different charge cups.
Click to expand...
 
TachoLycos said:
None of the 4 Jtek e-matches burned... Primary altimeter showed the whole flight to 2400 feet and showed events at apogee +1 and at 600 feet.
Click to expand...
Did the battery voltage show any changes when the events happened?

It sounds to me like all of the ematches were defective (unlikely) and/or the wiring harness was too high-resistance to get enough current into them. Did you make resistance measurements on the ematches?
 
Your primary failure is a mystery (unless it also lost power and you just can't tell).

As far as the backup, if you were using battery holders, terminal blocks or any extraneous links in the chain get rid of them.

What sort of switches were you using?
 
Thanks everyone for the replies. I have attached more pictures below.

Dave: One battery did seem to come loose. Will have to check that to stop that from happening again. I will look into the missile works altimeters as another option. That is a good idea using only one cup, it does seem like a waste if they both go when you use two. I have used two incase the main charge does not deploy the parachute and my second charge is always made slightly bigger for this reason.

Mike: I will check the readings tomorrow when I have them hooked up again. I didn't realize I could see the voltage readings during the flight through the software. I tested the e-matches after the failed flight, they all went off using the computer to command main/drogue through the altimeter. I have a couple that were installed that I have not lit, so I will check the resistance on them.

John: We do use terminal blocks, but may eliminate them in the future. They are generic 2 position switches. We will be mounting them horizontal in the future but they were installed as on being down for this flight.

Sumo: We were using regular alkaline 9Vs.

Thanks,
Chris
image.jpgimage.jpgimage.jpgimage.jpg
 
I'm not sure just checking voltage on the 9VDC batteries is enough. I had a very similar situation but with only one altimeter. The rocket lawn darted, but vacuum chamber testing and further flights have proven the altimeter was and still is good and reliable. I believe the contacts inside the battery were the issue. 9VDC batteries contain 6 AAA batteries wired together. If you have a poor or loose connection inside, you may not be able to tell until it tries to source a lot of current. That is what I believe happened in my case. I believe the battery was able to power the altimeter, but not source enough current to fire the charges.

I only use Duracell 9VDC batteries now. They cost more than most, but seem to be much more dependable. Once they prove reliable, I use them until the voltage drops below 9V. I trust a proven good battery more than an unproven new one. I'm actually on my second season with one. It still measure 9.4 V.
 
Careful with the slide switches if anything is protruding. A shock cord can turn these off. Not bad after the main, but between the drogue and main can be an issue. I always heard this and thought B.S. I had a beeper get turned off in mid air this way and had to walk through a lot of weeds as a result. Had I not found it, I wouldn't have believed that was the cause.

I use terminal blocks all the time. Saves me from opening the altimeters. I'm adding JST connecters to allow the end caps to come off easily without messing with the tiny terminals on the altimeter.

Duracell have the 6 batteries inside soldered together. Energizer are not soldered. Rayovac had some black clay material inside.
 
Curious case of failing altimeters :) Two suggestions: (a) Please post both .pf2 files, and (b) Do you remember what exactly the altimeters were beeping upon landing - was is pre-launch sequence (short beeps) or post-launch sequence (apogee readout) ?
 
Only one limited advantage to two powder cups. Admittedly this is rare since everyone does a ground test (don't they?)

If the main recovery laundry gets fouled in the rocket due to an inadequate charge, the second charge might do the trick to get it deployed.

I'm sure everyone has seen LPR and MPR stuff do this. I've had several where the cords fouled in the rocket and the "fluttering" got them deployed "in a nick of time" so the chute could inflate. Kurt
 
Thanks again for more replies. I have attached the data from the working altimeter below.

Handeman: I think we are going to use Duracell from now on. Used Rayovac because when I went to buy some brand new ones at the store, that was what they had.

Kevin: We usually put the switches under a cover for our bigger rockets, but didn't want to cut a cover into the cardboard we used for this flight. Will definitely be careful with placement and may put a block so that it can't be turned off accidentally.

Alex: a) posting below. b) I can't say I was paying close enough attention to know. I wanted to get them off so the charges didn't blow when people were handling the rocket.

Kurt: That is the reason that we used the two cups. We do do ground tests beforehand as well.

Looking at the voltage data from the flight, I would think the problem is in the battery itself. Looking at previous flights the voltage is very stable compared to the erratic nature of these batteries.

Thanks,
Chris

View attachment Subscale1.pf2

View attachment rawdatasubscale.txt
 
Last edited:
Bad battery or bad wiring. Your power was glitching as soon as 0.5 seconds..........

Dis you twist and tuck? If so that's an easy way to have a high impedance in the power circuit so you can't deliver the rated amps......

Test your battery under load to see what its real capacity is? Look at the voltage versus time through a fixed load. An almost dead battery will read nearly fully charged voltages if there is no load which is typical of a DVM.

What is the gauge of your internal wiring? Should be 22 gauge minimum, and 20 would be better so the internal wiring will not kill the available current.

Your e-matches will try to draw 9 amps at 9 volts. Your battery on a warm day will source 3 amps......and alkaline batteries do not recover quickly, especially if its cold and should this occur, you computer may reset, or the e-matches will not activate....due to lack of current.......use a lower battery voltage and a lower impedance battery.

A better power source would be a 2 LiPos in series to give about 8 volts. I would use 200-300 mah cells.

Bob
 
Here is a chart I generated from your Stratologger file:

Subscale1.png

Analysis:
1) Initial battery voltage was 9.6V, but it dips to 8V right at launch
2) At drogue event, battery voltage dips to 0V for 1 second - this is SL100 firing the charge
3) After firing the charge, the battery recovers to 6V, then slowly creeps to 9V
4) Battery voltage keeps going up and down as the rocket descends on drogue
5) At main event, battery voltage dips to 0V for 1 second - this is SL100 firing the charge
6) Battery recovers to 6V, slowly to 9V
7) Battery voltage drops to 0V upon landing


My (personal) conclusions:
a) Battery was weak - it was very slow to recover after firing charges (and did not have enough capacity to light them when fired)
b) There was a wiring problem that kept disconnecting the battery throughout the flight - especially evident at descent and landing
c) Stratologger functioned properly throughout the ordeal - it's amazing it was able to cope with such an unstable power without shutting down!


Not to show off, but for comparison purposes, this is how voltage should look for a good flight:

EscapeVelocity-H225.png


-Alex
https://RocketsEtc.com
 
azzie said:
Here is a chart I generated from your Stratologger file:

View attachment 247437

Analysis:
1) Initial battery voltage was 9.6V, but it dips to 8V right at launch
2) At drogue event, battery voltage dips to 0V for 1 second - this is SL100 firing the charge
3) After firing the charge, the battery recovers to 6V, then slowly creeps to 9V
4) Battery voltage keeps going up and down as the rocket descends on drogue
5) At main event, battery voltage dips to 0V for 1 second - this is SL100 firing the charge
6) Battery recovers to 6V, slowly to 9V
7) Battery voltage drops to 0V upon landing


My (personal) conclusions:
a) Battery was weak - it was very slow to recover after firing charges (and did not have enough capacity to light them when fired)
b) There was a wiring problem that kept disconnecting the battery throughout the flight - especially evident at descent and landing
c) Stratologger functioned properly throughout the ordeal - it's amazing it was able to cope with such an unstable power without shutting down!


Not to show off, but for comparison purposes, this is how voltage should look for a good flight:

View attachment 247439


-Alex
https://RocketsEtc.com
Click to expand...

Hi Alex,

What did you use to generate those graphs?
 
azzie said:
Here is a chart I generated from your Stratologger file:

View attachment 247437

Analysis:
1) Initial battery voltage was 9.6V, but it dips to 8V right at launch
2) At drogue event, battery voltage dips to 0V for 1 second - this is SL100 firing the charge
3) After firing the charge, the battery recovers to 6V, then slowly creeps to 9V
4) Battery voltage keeps going up and down as the rocket descends on drogue
5) At main event, battery voltage dips to 0V for 1 second - this is SL100 firing the charge
6) Battery recovers to 6V, slowly to 9V
7) Battery voltage drops to 0V upon landing
Click to expand...

That is definitly an issue with your power system.

It could either be voltage sag from a weak battery, or a loose connection.

Voltage sag is caused by trying to source more power than the battery can handle. The battery can only source a certain amount of power, so if it gets hit by a large current draw, the voltage will drop to compensate. However, it will look normal during resting conditions. I always use two 9V batteries in parallel, that way even if one or both are weak, their combined capacity can usually still make up for it.

In your case however it looks more like a loose connection, either internally in the battery, internally in your switch, one of the connections you made, or more commonly your battery clip deformed. I say this since the voltage graph looks intermittent, like something is disconnecting and partially reconnecting at points when the rocket would be under accelerations. If it was voltage sag it would only dive when you slammed it with a current request, and then it would slowly recover to regular voltage. It wouldn't show a fluctuation under accelerations. Also there shouldn't be much of a current draw at lift off, only during your deployments.

mpitfield said:
Hi Alex,

What did you use to generate those graphs?
Click to expand...

Stratologger's capture software will show voltages like that. Though it looks like he exported the data into excel.
 
I didn't read all your posts, but Azzie's plots clearly indicates the power problem we have all mentioned.......

Power switches should be mounted horizontal, not vertical. In a vertical positions the contacts can separate under acceleration, deceleration and/or vibration because they can mover away from each other. and this clearly happened throughout the flight. If mounted in a horizontal plane, both move in the same direction so there is less chance of a separation, and using a paralleled double pole switch provides some redundancy. Also using a better switch that can handle at least 10 amps is advised since your igniter is trying to pull 9 amps out of the power source and your can't supply that so any unnecessary resistance is bad. Please look at the StratoLogger manual on pages 11-13 for recommendations on switch type and location.

Similar orientation is recommended for your battery. The G-forces will try to disconnect the power on acceleration/or and deceleration when the battery is mounted vertical. Mounting the battery horizontal if possible with a strap around and over the connectors will prevent disconnects under g-loads. Positive battery clip retention is a must in a high acceleration system with vibration.

You should check the capacity of your battery by making a battery tester consisting of a 9 volt snap-on battery clip with a 5600 ohm solder across it to load the battery to the average drain of 1.5 ma. If you attach clip leads across the resistor, the voltage reading on a DVM should exceed 8.5 volts. If it doesn't, don't use it in the rocket as it is unlikely to have enough reserve power to supply several amps promptly activate the igniter.

Bob
 
Thanks everyone. I think the main issue is either the battery, with an internal short, or the switch itself.

Will make the necessary changes and launch again in December. Hopefully with much better results. :)

Not to show off, lol, but here was a launch of our carbon fiber launch a couple months ago. Perfect battery voltage as you showed as well.

We will be testing to find the actual problem, but you have all given me a good direction to go.

Thanks!
Chris

CarbonFiberLaunch.JPG
 
I had a similar problem when fly the I 1299 RMS motor.
Changed the battery clip and battery and all was fine afterwards.


JD
 
TachoLycos said:
here was a launch of our carbon fiber launch a couple months ago. Perfect battery voltage as you showed as well.

attachment.php
Click to expand...

I don't want to be negative of a good flight, but should not velocity change upon main deployment? If I calculate it correctly, it hit the ground at 75 ft/sec which is sort of fast :facepalm:

Remarkable that battery voltage did not dip for a fraction on a second on drogue event. Was it a backup altimeter with no drogue charge connected to it?

Was there anything else connected to the battery? Strange to see the battery drop 0.1V at lift-off and have no issues afterwards.
 
I figured someone would notice something wrong with that flight. lol. Gotta call me out. The drogue was attached to this altimeter and did fire. Not sure why there was no drop, but it did work fine. I'm sure if I look back at the line data it would show that.

It did hit a little fast. The main did not have a completely successful deployment causing the faster than normal ground hit. Luckily the entire rocket was made out of carbon fiber and sustained no damage. Still has the Bill Nye, both Mythbusters, and Homer Hickam signatures on the nose. :wink:

Thanks,
Chris
 
That's not just a little fast, it's way too fast. Like 4x too fast for a high power rocket recovery. Just don't want to make a habit of it.

Carbon rocket can take a beating. My friends 54 mm minimum diameter came straight in from 6000' and buried all but 1/4" into a sod farm. Dug out with no damage. Has had about 4 dozen flights since then. :wink:

Bob
 
bobkrech said:
My friends 54 mm minimum diameter came straight in from 6000' and buried all but 1/4" into a sod farm.
Click to expand...

Wow, I'd be interested in altimeter file for this flight. It must have broken ****** - at least, on the way down! ;)
 
azzie said:
Wow, I'd be interested in altimeter file for this flight. It must have broken ****** - at least, on the way down! ;)
Click to expand...

Probably about 300 mph on the way down. NASA has a terminal velocity calculator you can use to figure it out. My 2.25" diameter rocket with a Cd = 6.0 showed a terminal velocity of 296 mph from 2000 ft. That was at a launch site 200 ft above sea level. Higher altitudes will get higher speeds, but not much.
 

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