Redundant Electronics

[Wiley]

How necessary are redundant altimeters to a successful DD recovery? I know that a lot of people use a redundant altimeter for reliability, and this concept makes sense. Nevertheless, I was wondering how often this redundant altimeter is actually needed; i.e. when the primary one fails in some way to deploy the laundry. How many of you fly with just one altimeter? Success and failure stories are welcome.

[dixontj93060]

I fly in non-redundant mode probably 2/3rds of the time. Larger, more expensive or critical flights will be redundant.

[csoechtig]

I heavily researched this topic when I first got into dual deployment. In fact, you can find 2 or 3 threads in the forum archives with a variety of perspectives.

In general, most flyers use redundancy in large, expensive builds. You should look at it as an insurance policy to protect your investment.

I have 4 rockets with dual deployment and am building my 5th. I set up redundancy in my extended 5.5" Big Nuke and my extended 4" LOC IV. Smaller tubes can be dificult to pack it all in there.

I suggest you ground test all new altimeters with a shop vac on the port hole. Also, make sure you have new batteries for every launch. The combination of these two things will give you a high level of confidence.

I have witnessed very few altimeter failures at club launches. Usually, it is user error (wiring incorrectly).

[JDcluster]

If it's your only means of recovery you probably want some sort of insurance.
Any rocket >4" on up I use 2 altimeters or more. Anything under 4.0" is kind of hard to do. Most of my 4" rockets have flown on one altimeter.

Weight being one of the key elements for redundant systems.


JD

[Wiley]

As I said, redundant altimeters make sense, but I do not understand the replacement of the battery after each launch. I have heard this suggestion before, but throwing a four dollar battery away seems kind of wasteful .

[atxcple]

As I said, redundant altimeters make sense, but I do not understand the replacement of the battery after each launch. I have heard this suggestion before, but throwing a four dollar battery away seems kind of wasteful .

4.00 (battery) versus 600.00 adverage (rocket motor case, parachutes, electronics.) the flow chart that determines this would include,

which altimeter?

power drain at startup / diagnostics?

current needed for ematches / deployment charges?

how long are you sitting on the pad with power to electronics?

how long was it beeping out readings waiting for you to find it and power down?

my answer to this always is new battery / fresh recharge every time!!

[csoechtig]

As I said, redundant altimeters make sense, but I do not understand the replacement of the battery after each launch. I have heard this suggestion before, but throwing a four dollar battery away seems kind of wasteful .

Last month I was prepping for a launch and turned on my Stratologger Altimeter. The last series of beebs gives you the battery voltage. Typically, it beeps 9.2 or 9.3 times. In this case, it beeped 3.5 times. I tried again and got the same thing. When I replaced the battery, it jumped to 9.2. I found that strange considering I only used the battery on 2 launches.

Of course, you can trust the altimeter readings. However, considering that battery is powering your entire recovery system, $4 is cheap peice of mind.

[rocdoc]

As I said, redundant altimeters make sense, but I do not understand the replacement of the battery after each launch. I have heard this suggestion before, but throwing a four dollar battery away seems kind of wasteful .

A few thoughts:

First, I always buy the Duracell Procell batteries. They come bulk packed in 12-packs for only a buck or two each instead of $4 each. Here is a link to some I found with a quick Amazon search:

http://www.amazon.com/gp/product/B00...FYGGNR0MYPZ2PT

Second, I always use new batteries for each flight. As was stated by others, it is cheap insurance for a project that likely cost hundreds or thousands of dollars to launch anyway.

Third, I almost always use redundant electronics. Only reason not to is for super small rockets. You can throw a couple of Ravens in a really small space.

Fourth, if you are concerned about the waste of batteries, you have two options: You can usually power altimeters with rechargeable LiPo batteries which you can then reuse or you can do what I do and pop the "used" 9V batteries into your home smoke detectors to ensure that they always have a relatively fresh battery.

[SMR]

As I said, redundant altimeters make sense, but I do not understand the replacement of the battery after each launch. I have heard this suggestion before, but throwing a four dollar battery away seems kind of wasteful .

I recommend to use fresh batteries, but don't waste them. I rotate them, like rocdoc does... new ones go in rockets, and if they still still test good afterwards, they go into other things... smoke detectors, toys, radios, etc.

As for the redundancy question, if a hypothetical critical subsystem failed once in a hundred attempts (1%), that would still be a high failure rate. But doubling the subsystem doesn't just cut the total system failure rate in half (0.5%). Since the 1% failure would not likely be at the same time in both subsystems, the total system failure rate actually approaches 0.01% (one in ten thousand).

In 70 high power flights, I have had ONE ematch fail to fire. If it had been the only one, the rocket would not have had deployment. A redundant altimeter fired the backup charge, which paid for the extra altimeter four times over.

[delta22]

I check the voltage on my batteries before each launch and always use Duracells. My batteries stay over 9V for 6 to 8 flights, so replacing them sooner than that is a waste.

I always use one altimeter, but try to use motor ejection backup. Set motor delay to 2+ seconds after apogee just in case. This saved my Saturn V the one time I forgot to turn on the altimeter.

With well over 50 electronic deployments, never had an altimeter or ematch failure.

Will go with 2 altimeters for my L3 as it is required and motor ejection for backup is not available with 75mm motors.

[rocdoc]

I always use one altimeter, but try to use motor ejection backup. Set motor delay to 2+ seconds after apogee just in case.

That's funny. I absolutely HATE motor ejection. I flew redundant electronics on my L1 cert flight and nearly every flight since. Two of my kids got their NAR Junior L1 certs last year. They are not allowed to use electronics for ejection and are forced to use motor ejection. Since I had to build the motors, I had to trust RockSim to give me accurate delay times, then drill the delays to about that time. I have never been so nervous before a flight, including for my own L3 cert. Give me electronics any time.

[troj]

I recommend to use fresh batteries, but don't waste them. I rotate them, like rocdoc does... new ones go in rockets, and if they still still test good afterwards, they go into other things... smoke detectors, toys, radios, etc.

Ditto. I save them for smoke detectors, etc.

As far as the original question goes, if I can fit in two altimeters, I prefer to do so. That way if a wire pops loose, I screw something up on one, the match doesn't fire, the battery fails, whatever....I still have some insurance.

-Kevin

[chadrog]

I think it's funny that so many people rank their house burning down less important than successful deployment - me too.

[EddieJ710]

I've flown two perfectflites, each with it's own battery and switch, with two charges for the main and two for the drogue.... in a 54mm airframe. I like the insurance and until you get below 2" (54mm) airframes, size is no issue.

[rocdoc]

I've flown two perfectflites, each with it's own battery and switch, with two charges for the main and two for the drogue.... in a 54mm airframe. I like the insurance and until you get below 2" (54mm) airframes, size is no issue.

Ahh. . .

Isn't this the point where we debate whether it is better to use two identical altimeters or two from different manufacturers to decrease the risk of the same error occuring in two identical units?

[EddieJ710]

I see the value in dissimilar redundancy, however, if both units are well tested on the ground before hand and are shown to be in perfect working order, I can live with two of the same brand. Like I said though, dissimilar redundancy is never a bad idea.

[ClayD]

For the battery issue... a lot of people dont realize a 9volt battery is normaly 8.6 8-8 volts, and only around 100mah....
45min of a drain, you could be flirting with only having 7 volts available, and a brown out at some point in the flight.

So saying 6-8 flights on a 9 volt battery is fine, any less is a waste, is a dangerous thing to say...

I have 2 nine volt batteries powering my arts2, one of the batteries gets zapped really hard every flight... 8.8 volts going in... 7.2 volts after 1 flight. *with a small load applied* thats the pyro battery... the computer battery is safe for a few more flights...

i use rechargeable 9volt batteries... if i use (4) nine volt batteries per flight, I run out of uses really fast...

i am planning on moving to 11.1v lipo this year.. (since i have a few small ones.)

http://www.powerstream.com/9-v-batteries.htm

but as you can see on the discharge curve, i pack rayovac over duracell any day...

[barstoolmike]

I had a battery lead brake on my primary altimeter at lift off a couple years ago. If it wasn't for the back up altimeter the rocket would not have survived. Both charges for the primary altimeter where still in tack, so $79 for a back altimeter saved about $400 of rocket.

At the price of an Adept 22, $39 is cheap insurance these days.

Just my 2 cents.
Mike

[UPscaler]

we have a few dual deploy rockets...

standard 2 inch Darkstar: 1 Altimeter (Missileworks RRC2 mini)

4DD Little John: 1 altimeter (Perfectflite MAWD)

Extreme Darkstar: 2 altimeters (the previous mentioned two)

ultimate Darkstar (build in progress): 2 altimeters (above mentioned two, or possibly one of the two and a raven)

1/3rd scale Nike Smoke: 2 Altimeres (previously mentioned two)

Redundancy just eases our minds with these bigger rockets...




Braden

[Wiley]

How many of you have used the ADEPT22 and its companion backup unit, the DDC22, to take care of recovery on your birds?

[blackjack2564]

How many of you have used the ADEPT22 and its companion backup unit, the DDC22, to take care of recovery on your birds?

I have 6 A-22 and 2-DDC's. They are wonderful, don't let the price fool you.

An Adept-22 was alongside my Raven in 24,000ft drag race and the the altitudes were only 62 ft apart.

As to how many to use in each rocket? That's one you will have to figure out on your own. There are too many variables for me to go into here.

Sometimes even in a 6 in rocket I will only use 1. Then sometimes in a 2.1 I'll use 2. Depends on the size motor [s] and how extreme the flight or how high it's going. I don't follow the use 2 in everything if it will fit school of thought.

[UPscaler]

I have 6 A-22 and 2-DDC's. They are wonderful, don't let the price fool you.

An Adept-22 was alongside my Raven in 24,000ft drag race and the the altitudes were only 62 ft apart.

Man, we need to get a couple of those....




Braden

[Wiley]

Thanks Jim, I'll definately be using those two devices in the near future!

[nealkas]

I think it's funny that so many people rank their house burning down less important than successful deployment - me too.

Seriously! Please use them for anything but smoke detectors.
If you don't trust them for a rocket, don't trust them for your family.

[gldknght]

I was debating this issue with myself when setting up my e-bay in my DarkStar. I decided I will start to use redundant deployment when the cost of the rocket exceeds the cost of using two altimeters, four ejection charges, four ematches, at least two batteries, etc. Or, when I go for level 3 and redudancy is required by regulation.

I did set up my e-bay so at some point I can easily install a second altimeter if I ever decide to.

[rocdoc]

I was debating this issue with myself when setting up my e-bay in my DarkStar. I decided I will start to use redundant deployment when the cost of the rocket exceeds the cost of using two altimeters, four ejection charges, four ematches, at least two batteries, etc. Or, when I go for level 3 and redudancy is required by regulation.

I did set up my e-bay so at some point I can easily install a second altimeter if I ever decide to.

I didn't want my L3 project to be the first time I used redundant altimeters. There was enough stress already. I didn't want to add to it.

To add to your list of expenses above, if you're going to go with the expense of all that, you might as well use redundant e-matches as well. That way you have two e-matches (wired in parallel) for each charge to ensure that if one of your e-matches is a dud, the other will light your charge. That way you have double redundancy. You have redundant e-matches to increase the likelihood that each charge will fire and redundant charges to increase the likelihood that at least one of them will get the laundry out. Or at least make a nice "Bang" after the laundry is out and your secondary charge fires.

Bryan

[gldknght]

I didn't want my L3 project to be the first time I used redundant altimeters. There was enough stress already. I didn't want to add to it.

To add to your list of expenses above, if you're going to go with the expense of all that, you might as well use redundant e-matches as well. That way you have two e-matches (wired in parallel) for each charge to ensure that if one of your e-matches is a dud, the other will light your charge. That way you have double redundancy. You have redundant e-matches to increase the likelihood that each charge will fire and redundant charges to increase the likelihood that at least one of them will get the laundry out. Or at least make a nice "Bang" after the laundry is out and your secondary charge fires.

Bryan

LOL, I'm just going to rig up a co2 pressurized air bag to deploy right before the rocket hits the ground. No more parachutes, shock cords, chute protectors, and a (maybe) lighter rocket.

[tbonerocketeer]

For the battery issue... a lot of people dont realize a 9volt battery is normaly 8.6 8-8 volts, and only around 100mah....
45min of a drain, you could be flirting with only having 7 volts available, and a brown out at some point in the flight.

So saying 6-8 flights on a 9 volt battery is fine, any less is a waste, is a dangerous thing to say...

I have 2 nine volt batteries powering my arts2, one of the batteries gets zapped really hard every flight... 8.8 volts going in... 7.2 volts after 1 flight. *with a small load applied* thats the pyro battery... the computer battery is safe for a few more flights...

i use rechargeable 9volt batteries... if i use (4) nine volt batteries per flight, I run out of uses really fast...

i am planning on moving to 11.1v lipo this year.. (since i have a few small ones.)

http://www.powerstream.com/9-v-batteries.htm

but as you can see on the discharge curve, i pack rayovac over duracell any day...

That's odd. Every 9V i pull from the pack measure 9.4-9.8 Volts. I also use the 2 on the arts, and see some pull on the computer battery but nothing on the pyro battery.

[ClayD]

That's odd. Every 9V i pull from the pack measure 9.4-9.8 Volts. I also use the 2 on the arts, and see some pull on the computer battery but nothing on the pyro battery.

Realy? if you look and any otc "over the counter" 9v alkaline spec on energizer, duracell, (the one with the black cat), even Rayovac. they all say fall short of 9 volts. (the spec at 9.6 ---- without load)

Probably what your doing is checking the battery with no load. this is not a good thing. as you can see on the attachment, duracell battery, is never above 9volts, except 1 tests it "starts" just above 9 volts.

my arts 2 tests out to pull .05amp at a 9.1 volts applied, fluxuates to 9.0v at the beep with a .06amp draw. (on the computer side) i have not tested the draw on the pyro battery yet... i want to set it up outside and fire some ematches to see what the latch current is, i assure you it pulls way more than the computer side.)
after the flights, with load my pyro battery looses almost 1 volt. my computer battery looses about .4 volts.

usually 3/4 to 1 hour on. from arming to turning off.

are you testing with a mulitmeter with a "battery tester", your load thingybobber may be broken? take a worn battry test with no load you will get a higher voltage, than if you put a small load on it.

My smd station measures well above 9volts, but doesnt apply load. This is not a safe measurement for testing batteries.

[ClayD]

http://support.radioshack.com/suppor.../batgd-B08.htm