Rocketry Planet

YARDLEY, Pennsylvania USA — Owners of the Ozark Aerospace's new ARTS2 flight computer are being warned about the use of high-current electric matches when using the device in "single battery mode."  The ARTS2 features a current limiting design to prevent processor "brown-out," which prevents it from firing higher current electric matches with one battery.

Ozark Aerospace's ARTS 2 flight computer.

Two northwestern rocketeers who experienced recovery failures this past weekend using the new Ozark Aerospace flight computer were using the device in "single battery mode" along with electric matches from M-Tek.  M-Tek's e-matches have been known to work reliably in the past with the original Ozark Aerospace ARTS flight computer, and was thought to be a carry-over.

One rocket landed ballistically and other didn't deploy its main parachute, experiencing a hard landing.  Follow-up testing revealed that the ARTS2 would not reliably ignite the M-Tek e-matches.  Ozark Aerospace recommends DaveyFire 28B's with the ARTS2 when used in "single battery mode."  Users wishing to utilize the higher current e-matches like the M-Tek should use the dual-battery option and test their flight configuration.

Since its introduction in 2004, the ARTS flight computer by Ozark Aerospace has earned a reputation for reliability and outstanding features. The updated ARTS 2 includes several new features, while retaining the dimensions and mounting hole locations of the original.

Reader comments:

#1

A good argument for ground testing, even though ground testing will not always show deficiencies. This may be an example of intermittant operation. In other words the ARTS2 with a single battery may fire some of the MTECs but not all.

Sounds like using the two battery option on all flights is the best way to go.

Curious ?, are the DaveyFire 28B's even available? Seems like I heard they were not. If so what is Ozark suggesting now?

QuickBurst on 03-07-2007 07:21 AM

#2

It sounds like an undocumented "feature" of the new model. This from the electronics that already had the lowest latch time of any deployment device on the market.

crontab on 03-07-2007 08:38 PM

#3

True. The ARTS has a latch time of .25 seconds. Lowest around. For example, the Missile Works and PerfectFlite altimeters have a one second latch time.

Adept is low on the list as well.

The ARTS is still on my "must have" list. I hope to pick one up this weekend.

QuickBurst on 03-08-2007 08:03 AM

#4

This is bound to happen if their circuit limits current to the output in order to maintain the processor. A person must choose a battery with low internal resistance. Another thing that would help is to attach a large capacitor (1000 microfarad or so) in parallel with the battery input (if you use a switch between your battery and your altimeter then you should put the cap on the altimeter side of the switch to debounce your switch also). The capacitor will support the voltage for a while the output latches. Caps are lighter than batteries with very little internal resistance.

Steve_Shannon on 03-08-2007 08:39 AM

#5

Steve,

I don't see how putting a cap on the input helps if the current limiter is tied to the output. Are you saying the current limiter only kicks in if the input voltage begins to drop? That is not likely the way it is designed (maybe someone from Loki or ARTS can comment here). If the solution was as simple as this, then why go to the effort of doing the ARTS2 with a second battery feed.

-Tim

Quote:

This is bound to happen if their circuit limits current to the output in order to maintain the processor. A person must choose a battery with low internal resistance. Another thing that would help is to attach a large capacitor (1000 microfarad or so) in parallel with the battery input (if you use a switch between your battery and your altimeter then you should put the cap on the altimeter side of the switch to debounce your switch also). The capacitor will support the voltage for a while the output latches. Caps are lighter than batteries with very little internal resistance.

dixontj on 03-08-2007 03:08 PM

#6

If it doesn't work this way then it will limit current every time you use a higher current match or igniter, regardless of how well your battery can maintain its voltage, and that certainly isn't desirable.

Hopefully it is looking at the voltage to the processor, rather than just clamping based on current sent to the output. Like you said, maybe someone with real knowledge can chime in.

Steve_Shannon on 03-08-2007 08:15 PM

#7

The AltAcc outputs stay on for only 0.1 seconds. At least that is what the manual says.

This is most likely because the output FETs are in a SO8 package and would be in significant danger of burning out with longer on times in the event of a short circuit. The ALTS2 also appears to use SO8 size devices.

UhClem on 03-08-2007 10:11 PM

#8

Quote:

If it doesn't work this way then it will limit current every time you use a higher current match or igniter, regardless of how well your battery can maintain its voltage, and that certainly isn't desirable.

Hopefully it is looking at the voltage to the processor, rather than just clamping based on current sent to the output. Like you said, maybe someone with real knowledge can chime in.

I'll chime.

The ARTS2 has two battery connections. The "Main" connection powers the processor as well as the pyro outputs. The "Pyro" connection only supplies power to the pyros.

To protect the processor from brownouts, current to the pyro channels from the "Main" battery connection is limited. You can fly it configured this way, you just need to use low current ignitors.

Current from the "Pyro" battery connection to the pyro outpus is not limited in any way. (except, of course, by the internal resistance of the FETs) This allows the pyros to go to town draining this battery while the processor is still safely powered from the "Main" battery.

Ozark Aerospace has gotten where it has by listening to what you have to say. Please, if you have any comments or suggestions, send 'em to me. I want to hear. If you post something on a forum, and it is not answered, please contact me directly. There are a lot of forums out here, and I do miss things.

Thanks,
Erik

ErikHall on 03-10-2007 10:05 PM

#9 Arts - Arts2?

Can anyone point me to documentation that lists the differences between the ARTS and ARTS2?

Thanks!

k3td on 03-19-2007 06:37 AM

#10

Quote:

Can anyone point me to documentation that lists the differences between the ARTS and ARTS2?

I wrote Erik with that same question and haven't gotten a response.

ddmobley on 03-19-2007 04:38 PM

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