Good Backup DD Altimeter to FW Raven?

Guys -

I'm going to be using a FW Raven as my primary DD Altimeter for a couple of different rockets - but in looking at many of your builds and learning more and more about DD, it looks like having a back-up is the way to go - for pure redundancy sake.

Adrian's Raven looks to be a first rate, rather bulletproof product, but hey, it's rocketry, and I've seen enough to know that backups are a good thing.

So what would be a good compliment (different algorithms, etc.) to the Raven as the backup for DD?

I ask this because, in a few cases, I'll use the Raven to also trigger a staging event - which takes away from the back-up DD settings...

Anyone make a five output altimeter? Staging Event, Apogee Depoy, Apogee Backup, Main Deploy, Main Backup? I guess I could always re-direct the Apogee backup as the staging event, and use motor ejection as the apogee backup?

Thanks!

I like the Perfectflite miniAlt/WD if your application can stomach a "baro only" altimeter.

While redundancy is a great thing, a lot can be said for KISS.

A second altimeter means a second set of harness to be designed, fabricated, debugged, and inspected.

It is a second set of programming and turn on procedures to be thoroughly understood.

It is an extra thing to do at the pad that you need to make sure does not distract you from performing some critical function.

It is an extra set of charges to be prepared.

It is an extra battery (or batteries) to be evaluated.

Redundancy won't help you if you forget to turn it on. :gavel:

So, I think it is a lot more complicated than "more is better." But I don't want to scare you off. I think you just need to be careful when designing your recovery system and balance redundancy with practicalities.

Oh good another potential religious war thread

Logic or algorithm failures on altimeters are exceedingly rare. Most common failures are due to a wiring failure or user error.

If you want to use a second altimeter I recommend simply getting another Raven so you do not have to learn a new system which reduces the opportunity for user error.

jderimig said:

Most common failures are due to a wiring failure or user error.

Click to expand...

We have met the enemy and he is us. :bangpan:

Thank you for this thread, I was just disusing this with my boyfriend. He really likes having a backup. He normally runs two different brands, as an extra precaution. The one thing I like about my Raven is that I can link it to my computer. Is there another small one that can do this, and does DD?

Kira_Majeric said:

Thank you for this thread, I was just disusing this with my boyfriend. He really likes having a backup. He normally runs two different brands, as an extra precaution. The one thing I like about my Raven is that I can link it to my computer. Is there another small one that can do this, and does DD?

Click to expand...

You can download flight data from the PerfectFlite MAWD, ARTS, RDAS, and several others.

-Kevin

troj said:

You can download flight data from the PerfectFlite MAWD, ARTS, RDAS, and several others.

-Kevin

Click to expand...

Thank you. ^_^

Kira_Majeric said:

Thank you for this thread, I was just disusing this with my boyfriend. He really likes having a backup. He normally runs two different brands, as an extra precaution. The one thing I like about my Raven is that I can link it to my computer. Is there another small one that can do this, and does DD?

Click to expand...

The Entacore AIM altimeter also does data logging.

My personal favorite small altimeter for its combination of ease of use and features is the RDAS tiny. It's quite expensive though.

I hear you guys about simple - and getting a second Raven is definitely a possibility.... I certainly didn't intend to start some unholy discussion, but I figured it would be interesting to see what everyone thought would be a compliment to the Raven.

And if the failures are all due to bad setup, then it seems that these things are prone to bad setup, as I've read about all too many accidents on this board alone (from what appear to be some darned experienced fliers).

Plus, I've been versed on issues with accelerometer based apogee deploy caused by the rocket softly arcing over due to wind, where it's hard for the sensor to determine that apogee has occured.

Miss that, and deploy the main at 500 feet, that's a sure fire recipe for a zipperfest at best, and a shredfest at worst....

So let's keep it sane, and see where the discussion goes.

Thanks!

pcotcher said:

then it seems that these things are prone to bad setup, as I've read about all too many accidents on this board alone (from what appear to be some darned experienced fliers).

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That is correct. Some units are easier to correctly configure or install than others. If you use two hard-to-configure units then you will double the probably of setting at least one up incorrectly.

pcotcher said:

Plus, I've been versed on issues with accelerometer based apogee deploy caused by the rocket softly arcing over due to wind, where it's hard for the sensor to determine that apogee has occured.

Click to expand...

Redundancy will not help you here either. There are altimeters that can be programmed to detect apogee based on accel OR baro. You can configure your Raven to use baro for one channel and accel for another channel.

I think the Raven's default behavior is to use baro for apogee, with some additional criteria based on the accelerometer to ensure that mach can't trigger the charge. That should be accurate nearly 100% of the time.

pcotcher said:

I hear you guys about simple - and getting a second Raven is definitely a possibility.... I certainly didn't intend to start some unholy discussion, but I figured it would be interesting to see what everyone thought would be a compliment to the Raven.

And if the failures are all due to bad setup, then it seems that these things are prone to bad setup, as I've read about all too many accidents on this board alone (from what appear to be some darned experienced fliers).

Click to expand...

As a general rule, the more features, the more complexity there is involved in setting the altimeter up properly.

That's why I typically recommend the MAWD and RRC2 to folks who are new to electronics, though the RRC2 Mini isn't as easy as the old RRC2.

-Kevin

troj said:

the RRC2 Mini isn't as easy as the old RRC2

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I really miss the RRC2. It was a bulletproof backup altimeter.

I agree with Will--wiring, connectors, switches, and checklists are more important to success than the particular altimeter(s). And simple is better. Saying that, I will use redundancy in most designs--I've just personally experienced the benefit too many times. But back to the KISS principle, I would tend to pick something simple. The Raven/Parrot family are great (I have one), but fairly complex. And although, I understand the logic of picking two alts of the same kind, I wouldn't recommend that. We are creatures of habit and often don't recognize our own mistakes, thus a setup error on one might be duplicated on an identical alt. So my choice would likely be a Hi-Alt 45K or an RRC2-mini, most likely the later as I like its flexibility and wide range of settings that can be done at the launch site without a computer so as to accommodate launch conditions. (BTW, I suggest the HA45K over the MAWD as the later's logging is pretty crude and in my opinion not really worth the price delta unless you need it as your very first logging alt).

I think for what i need the hialt45 is the one I will be going with. but not until next year after my dance season and XPRS..... I think I just have too many expensive hobbies.... ^_^

WillMarchant said:

I really miss the RRC2. It was a bulletproof backup altimeter.

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I flew mine until I eventually lost it. Jim Amos is now selling leftover old PC boards for the RRC2, and I ordered one, along with the chip, and have mostly put it together. Still a few parts to go, but I hope to have a working one again in a couple of weeks.

Re. redundancy, I also would be much more concerned about user error than I would about altimeter failure. Arming switch failure is also quite a bit more likely, and I think that a tangled chute due to improper packing is also quite a bit higher in the list than altimeter failure (I've failed that test myself several times). I also haven't had a lot of ematch failures. I think that redundancy doesn't make sense if you're using it because you're worried that the altimeter will fail. It might make sense if you're using it as a hedge against bad wiring, bad switches, etc. I think one should also be aware that multiple altimeters increase some risks - it's not a free lunch, even if it is often a good deal.

I use the Transolve P6-K as a backup and sometimes the primary. I have a Raven and yes I have made plenty of user errors. What I like about the P6-k is that it is simple to use and passes plenty of current to fire a charge. You just have to remember to turn it on.

pcotcher said:

So what would be a good compliment (different algorithms, etc.) to the Raven as the backup for DD?

Click to expand...

Here's a possibility for you... on our NASA-SLI rocket (4" Blue Tube 92" tall, flew to 5639 on a K1200 and lost narry a Ladybug passenger) we used the MAWD as the primary, and the Raven as the backup, slightly modifying the default paramters for the #3 and #4 outputs (which come ready as backup). Though the MAWDs peformed just as they were supposed to, the Raven gave us the acceleration recording that we wanted, plus the easy backup capabilities. If you were to try that configuration, you could program the #1 or #2 output for your triggered output and wouldn't have to change much else.

jderimig said:

I recommend simply getting another Raven so you do not have to learn a new system which reduces the opportunity for user error.

Click to expand...

Yeah, I can see that.
I also have to wonder if two different brands/designs would avoid any potential "double absent-mindedness" problems. I mean, if you slip up with setup for one, and the second one is the same model, you will tend to simply repeat your mistake...right?

Qstn: when worrying about redundancy, do you guys generally set up two completely different sets of electronics, all the way down to the igniters, and then use two completely different BP deployment charges? or do you put both igniters into one BP cannister? Pros & cons? Anyone ever had problems with excessive (simultaneous) deployment pyro?

For my L3 build/flight I'll be using a Raven as a primary and a RRc2 mini for redundant ejection charges. If successful I'll use the 3rd channel output of the Raven for a future clustered airstart in said rocket.

I'll have them both fire at barometric apogee and at 1000' for the main.

But...Like Paul said, there's all kinds of things more likely to fail after the electrical events occur.

sylvie369 said:

I flew mine until I eventually lost it. Jim Amos is now selling leftover old PC boards for the RRC2, and I ordered one, along with the chip, and have mostly put it together. Still a few parts to go, but I hope to have a working one again in a couple of weeks.

Click to expand...

Really?!

Are they listed on the website? If the price is reasonable, I'll grab one or two! Soldering isn't an issue, and if it has parts I don't care to deal with, I have friends who are better at it.

-Kevin

Looks like $10 each for the board and chip. Is there a schematic or parts list available?

powderburner said:

I also have to wonder if two different brands/designs would avoid any potential "double absent-mindedness" problems. I mean, if you slip up with setup for one, and the second one is the same model, you will tend to simply repeat your mistake...right?

Click to expand...

My/our thinking on this is that if you're going to have a failure of the electronics, then having a different flight computer may lessen the chance of both altimeters having the same failure mode. If it's a human-interface problem, then having two different altimeters definitely lessens the chance of both altimeters being set up wrong.

powderburner said:

Qstn: when worrying about redundancy, do you guys generally set up two completely different sets of electronics, all the way down to the igniters, and then use two completely different BP deployment charges?

Click to expand...

If you want redundancy, why would you go half-way? On our SLI rocket, which really had to work correctly if for no other reason than pride and fear that we'd embarass ourselves over a nationwide audience (you WERE watching the live webast, like everyone else in your familiy, weren't you? ) we had each altimeter's apogee and main channel, firing into its own igniter, which had its own BP charge. All four fired just like they were supposed to.

Now, if you're playing around in your backyard and you don't really care whether your rocket performs as designed....

slogfilet said:

Looks like $10 each for the board and chip. Is there a schematic or parts list available?

Click to expand...

Not to hijack the thread, but yes, there's the "RRC2 Scratch Builder's Supplement", a pdf on this page:

https://www.missileworks.com/index.php?main_page=page&id=1

It includes lists of parts/part numbers for a few suppliers (Digikey, Radio Shack, Allied), rough wiring diagrams, and some construction instructions. These are really the directions for wiring up your own, not for building on the circuit board, which makes things a little confusing.

Most notably, there doesn't seem to be an "R20" (resistor 20), despite a spot for one on the board. If anyone still has an original RRC2, I wouldn't mind talking to you about that.

I did build the firing circuit on a prototyping board from the directions in the supplement, just to better understand firing circuits. It works just fine.

And Kevin, yes, they're listed on the website. I ordered a board and chip, about two months ago, IIRC, very shortly after the boards appeared on the site. I've been scrounging parts ever since. Some are obsolete, which is I assume part of why he discontinued the RRC2 and created the RRC2 Mini. That's always the threat hanging over small electonics manufacturers.

Interestingly, after ordering the DIP switches from Digikey, I got a call a few days ago from the regional tech rep of the company that makes the switches. He wanted to ask if there was anything he could help with, and he wanted to know what my application was. This is the second time a company's rep has called me after I ordered parts from Digikey, and it's great fun telling them what the application is. They're definitely not expecting "high power rocket altimeter and deployment controller".

jderimig said:

That is correct. Some units are easier to correctly configure or install than others. If you use two hard-to-configure units then you will double the probably of setting at least one up incorrectly.



Redundancy will not help you here either. There are altimeters that can be programmed to detect apogee based on accel OR baro. You can configure your Raven to use baro for one channel and accel for another channel.

Click to expand...

In fact, that is the default behavior for the Raven, so you don't even need to touch the deployment settings if you don't want to. Channel 1 is an accelerometer-based detection of apogee. Channel 3 is a baro-based apogee output, with a 1.5 second delay. Outputs 2 and 4 are the main deployment and main backup deployment, respectively.

One user purchased 2 Ravens, and just wired the apogee and main charges to one Raven, and wired his backup charges to the backup apogee and backup main channels of the second Raven. He didn't have to change any settings, and also didn't run the risk of an overpressure event from two simultaneous charges.

I think it's kind of a funny quirk of human nature that if device A can be adjusted, but doesn't need to be, and device B can't be adjusted, that device B is deemed easier/simpler to operate than device A.

sylvie369 said:

Most notably, there doesn't seem to be an "R20" (resistor 20), despite a spot for one on the board. If anyone still has an original RRC2, I wouldn't mind talking to you about that.

Click to expand...

My RRC2 has a resistor in every position on the board. I can't tell which is which as the component id silkscreen is under the resistors. My unit is a revision B.

Rocketjunkie said:

My RRC2 has a resistor in every position on the board. I can't tell which is which as the component id silkscreen is under the resistors. My unit is a revision B.

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I don't know if this will correspond to yours, but there's 6 resistors sitting next to each other just inboard from the J2 output terminal (the one for the main parachute). They're between that terminal and the piezo beeper.

R20, on this board, anyway, is the 4th one in from the terminal (or 3rd one in from the beeper, if you start on that side). If that's not clear, I'll upload a photo, but does that make sense?

Thanks.

sylvie369 said:

R20, on this board, anyway, is the 4th one in from the terminal (or 3rd one in from the beeper, if you start on that side). If that's not clear, I'll upload a photo, but does that make sense?

Click to expand...

A photo would be ideal, as resistor values can be determined based on the color bands.

-Kevin

troj said:

A photo would be ideal, as resistor values can be determined based on the color bands.

-Kevin

Click to expand...

Well, the photo I'd be uploading would just have a resistor outline in the silk screen and the label "R20". I'm the one who _doesn't_ have the resistor in place.

But yes, an close-up photo of a populated board would be great, as long as we can see the color bands clearly.

Edit - Oh, of course. Google is your friend:

https://tinyurl.com/34bom2e

Got it.