First AV Bay Design

the rocketry show
eggtimer rocketry
The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
W

wsume99

Well-Known Member
TRF Supporter
Joined
Feb 28, 2014
Messages
510
Reaction score
265
Location
Ohio
In the planning phase of my first electronic deployment rocket. I'm building a 3" Punisher with HED. Been doing a lot of research on altimeters, switches, batteries, and bay design/layout. I've been posting and commenting but decided to create a separate thread to consolidate all my thoughts. I'm guessing that if I am going thru this now that someone else probably is too or will be in the future plus I'll be able to refer back to this thread when I forget something. [emoji1787][emoji1787] So this thread is likely to be all over the map with random questions and observations as I go. I appreciate feedback and I know there are many knowledgeable fliers out there I can learn from.

I want the highest chance possible (within reason) of recovering my rocket. So to me that means I need two altimeters and GPS tracking in my AV bay. Right now I am thinking of the following hardware:
1) Eggtimer Quantum
2) Eggtimer Classic (I already have one)
3) Eggtimer Wifi switch (to control the Classic)
4) Eggtimer TX mini

Question - I see a lot of people use different types of altimeters when employing redundancy. I assume this is to avoid some freak event where both fail/malfunction for the same reason. So what about different models from the same vendor, like I have chosen? What's the view there? What if I were to use two Eggtimer Quantums? Would having two of the same altimeters be less risky than two different altimeters plus a wifi switch? So I'm adding a third component to introduce variety but an additional component adds risk of failure. (I'm pretty much set on using the wifi switches.)
 
A few of points to consider.

If you're planning to have a redundant altimeter setup (Quantum and Classic, or 2 x Classic), you will also require 2 x Wifi switches. For proper redundancy you will require two independent power sources: 2 x batteries and 2 x Wifi switches. Why not choose the Proton kit instead, as it already has WiFi switching. The cost will be similar with that combo. Given that you already have a Classic, rather than buy another Classic or Quantum and another wifi switch, just get a Proton with its own battery.

I assume you were going to use the WiFi switch to power the two altimeters and the Eggfinder Tx Mini? Not a good plan in my opinion! Power the Tx separately if you want true redundancy.

There are many flyers that will use different altimeter models from one manufacturer, or from different manufacturers, to reduce the risk of potential inherent issues with two of the same. Personally, I have never had issues with using the same model as a redundancy choice. Commercially manufactured altimeters are generally very reliable. However, if you're building your own from kits, there might be issues with consistency - this will depend on your fabrication skills.

There is another thread here that discusses the potential issues with co-locating a tracker and antenna in the avbay with the altimeters. If that's what you wish to do, then it's probably advisable to mount the antenna on the outside of one of the avbay bulkplates. This will reduce the possibility of interference with the altimeters and improved the radiation pattern of the antenna. Again, many people don't get too hung up on this, but I see no reason to tempt fate when you have all that investment in your rocket. I would also prefer to install the Tx in the nosecone.

Good luck with the build.
 
I can’t see an issue using two altimeters from same manufacturer. That said, I don’t trust my own soldering skills to use two Eggtimer kits exclusively in my rockets. The kits are awesome but I’ve paired them Missleworks altimeters for my own piece of mind.

I’m also assuming you’re newer to DD and tracking. I would suggest tackling a little at a time rather than putting it all in at once. Say prove out the GPS tracking and get down your technique before adding DD. I’m kind of a methodical guy and like to keep it simple. Easier troubleshooting when stuff goes wrong. I flew a single altimeter for several flights before I doubled up. And even that was a dead simple rrc2+.
 
The Quantum already has wifi switching, so it's good just on its own. I would be perfectly comfortable flying two Quantums plus a Mini Tx in a dual deploy rocket, though it would be nice to flight-test both Quantums before you put them in the big rocket. My understanding that the suggestion to use different brands is a relic of the days when altimeters were less reliable and different brands were more likely to have software issues. The plus side of using both altimeters from the same brand is that the apogee and main settings will cooperate with each other so you are less likely to have two charges go off at once.

Other combinations you might consider:
Classic + Quark (both on separate wifi or screw switches)
Quantum + Quark (Quark on a wifi or a screw switch)
Quantum + Missileworks RRC2+ (RRC2 on a wifi or screw switch)

Regardless of what you do, you should have three batteries for full redundancy.
 
Steveo said:
I’m also assuming you’re newer to DD and tracking. I would suggest tackling a little at a time rather than putting it all in at once. Say prove out the GPS tracking and get down your technique before adding DD.
Click to expand...

Oh, I definitely plan to do exactly as you are suggesting. I posted this in another thread but I'll add it here so it's all in one spot. Here is my plan to go from no electronics to dual redundancy with tracking.

Step 1 - single altimeter with motor backup
Step 2 - dual altimeters with plugged motor
Step 3 - dual altimeters plus GPS tracking

I would repeat several flights with each configuration until I feel comfortable with it before moving on to the next step.
 
Last edited:
Voyager1 said:
A few of points to consider.

If you're planning to have a redundant altimeter setup (Quantum and Classic, or 2 x Classic), you will also require 2 x Wifi switches. For proper redundancy you will require two independent power sources: 2 x batteries and 2 x Wifi switches. Why not choose the Proton kit instead, as it already has WiFi switching. The cost will be similar with that combo. Given that you already have a Classic, rather than buy another Classic or Quantum and another wifi switch, just get a Proton with its own battery.

I assume you were going to use the WiFi switch to power the two altimeters and the Eggfinder Tx Mini? Not a good plan in my opinion! Power the Tx separately if you want true redundancy.

There are many flyers that will use different altimeter models from one manufacturer, or from different manufacturers, to reduce the risk of potential inherent issues with two of the same. Personally, I have never had issues with using the same model as a redundancy choice. Commercially manufactured altimeters are generally very reliable. However, if you're building your own from kits, there might be issues with consistency - this will depend on your fabrication skills.

There is another thread here that discusses the potential issues with co-locating a tracker and antenna in the avbay with the altimeters. If that's what you wish to do, then it's probably advisable to mount the antenna on the outside of one of the avbay bulkplates. This will reduce the possibility of interference with the altimeters and improved the radiation pattern of the antenna. Again, many people don't get too hung up on this, but I see no reason to tempt fate when you have all that investment in your rocket. I would also prefer to install the Tx in the nosecone.

Good luck with the build.
Click to expand...
The Quantum has its own onboard switch. If I use the classic then I need a separate switch for redundancy so that is why I added the wifi switch. That would give me two altimeters each with their own switch.
 
I am working on the electronics for a Punisher 3 right now. I am only using 1, an Eggtimer Classic with a screw switch, but I could easily add a Quark for redundancy. I was just going to mount the Eggfinder Tx to the shock cord. Other builds will have it in the nosecone.

I'm planning the first flight to be single deployment with motor backup before flying it dual deploy and with plugged motors.
 
boatgeek said:
Regardless of what you do, you should have three batteries for full redundancy.
Click to expand...

After settling on the altimeters and switches batteries was going to be my next question. Assume I go with 2 quantums and a mini tracker. I assume you are referring to a separate battery for each altimeter along with the tracker?

For each altimeter, what about separating the board power from deployment power? I've seen many people powering both sides with a single lipo, even the designer of the boards recommends it. It sounds like with proper battery selection (according to the quantum user guide) that the risk of a brownout event during deployment firing is almost zero. If I were to separate the board power from deployment power that would mean 5 batteries. [emoji54][emoji54] That seems excessive and all the wiring and connections from the extra batteries would be a greater risk than a brownout assuming I use the right battery.
 
NateB said:
I am working on the electronics for a Punisher 3 right now. I am only using 1, an Eggtimer Classic with a screw switch, but I could easily add a Quark for redundancy. I was just going to mount the Eggfinder Tx to the shock cord. Other builds will have it in the nosecone.

I'm planning the first flight to be single deployment with motor backup before flying it dual deploy and with plugged motors.
Click to expand...
Ideally I would like to place the tracker inside the coupler and have the antenna mounted to the aft bulkhead. I plan to place it near the outer diameter so it will fit between the motor case and body tube. Not sure if that is possible but I'll make a model of everything before I start building the AV bay.
 
I am keeping it simple on my Punisher. I only have the one tracker, so I wanted to be as easy as possible to move around. In my mind, a TRS with a Quark or RRCT2+ for backup would be ideal and I might use that on future builds.
 
wsume99 said:
After settling on the altimeters and switches batteries was going to be my next question. Assume I go with 2 quantums and a mini tracker. I assume you are referring to a separate battery for each altimeter along with the tracker?

For each altimeter, what about separating the board power from deployment power? I've seen many people powering both sides with a single lipo, even the designer of the boards recommends it. It sounds like with proper battery selection (according to the quantum user guide) that the risk of a brownout event during deployment firing is almost zero. If I were to separate the board power from deployment power that would mean 5 batteries. [emoji54][emoji54] That seems excessive and all the wiring and connections from the extra batteries would be a greater risk than a brownout assuming I use the right battery.
Click to expand...

Me, I'm good with one battery powering the altimeter and charges. Reasonable people disagree though. If you do have them all powered together, you definitely want a good LiPo battery for each altimeter and to charge it fully before launch.
 
NateB said:
I am keeping it simple on my Punisher. I only have the one tracker, so I wanted to be as easy as possible to move around. In my mind, a TRS with a Quark or RRCT2+ for backup would be ideal and I might use that on future builds.
Click to expand...
Agree with you on the TRS plus quark being about perfect. At least it seems so on paper. I already have two Eggtimer classics so I was trying to use them and I may still do that. Maybe I'll use them and switch to the TRS when I want tracking. Building them will give me more experience so why not. Plus I'm sure having more altimeters will come in handy as my HPR fleet expands.
 
wsume99 said:
Agree with you on the TRS plus quark being about perfect. At least it seems so on paper. I already have two Eggtimer classics so I was trying to use them and I may still do that. Maybe I'll use them and switch to the TRS when I want tracking. Building them will give me more experience so why not. Plus I'm sure having more altimeters will come in handy as my HPR fleet expands.
Click to expand...

If you already have two Classics, then I'd recommend a Quark. They're easy, cheap, and small. The only real drawback is that they don't do data, but you're flying a Classic anyway so you can get your data there.
 
boatgeek said:
If you already have two Classics, then I'd recommend a Quark. They're easy, cheap, and small. The only real drawback is that they don't do data, but you're flying a Classic anyway so you can get your data there.
Click to expand...
Good point. If the classic crapped out I would be happy to get my rocket back and not care about the loss of the detailed flight data. Although a quark + wifi switch = $40 which is the same cost as the quantum. Seems like the cheapest route for me would be to just get 2 wifi switches. Actually getting a TRS would be the cheapest option for my end state. I would need to add a wifi switch and an eggfinder mini to one of my classics which would be $95 and the TRS is $90.

Looks like I'm back to a TRS with a classic plus wifi switch as my setup. I'll fly the rocket first with just the classic and wifi switch with motor backup. Then after I have a few flights under my belt make the final decision on what I want to do and buy the additional hardware.
 
This thread cracks me up. The OP is building his first av-bay and you guys have him thinking 5 batteries are needed?!?!?

You want "the highest chance possible (within reason) of recovering my rocket." Then move GPS tracking to the top of your list, not the bottom.

Properly secure your battery and thoroughly ground test your deployment charges, and you will only need one altimeter with one battery. Ever. The commercial altimeters are far more reliable than the human trying wire all that redundant crap together. All this redundancy seems like a crutch for shoddy design, clumsy execution, and poor understanding. Yeah, yeah, all you NASA guys will tell me how important redundancy is for flight missions, but this is a hobby model rocket.

If you like complexity, then knock yourself out. Personally, I would rather be flying, than prepping 3 electronics, 3 switches, 5 batteries, and God knows how many ematch charges.

<helmet and kevlar suit ready>
 
My take on this is that about 99% of the deployment failures that I've seen are mechanical... including batteries moving around and the connectors coming undone. Secure everything so that nothing can move and your deployment controllers will be fine, and yes, put the GPS in the nose with its own battery.
 
wsume99 said:
Good point. If the classic crapped out I would be happy to get my rocket back and not care about the loss of the detailed flight data. Although a quark + wifi switch = $40 which is the same cost as the quantum. Seems like the cheapest route for me would be to just get 2 wifi switches. Actually getting a TRS would be the cheapest option for my end state. I would need to add a wifi switch and an eggfinder mini to one of my classics which would be $95 and the TRS is $90.

Looks like I'm back to a TRS with a classic plus wifi switch as my setup. I'll fly the rocket first with just the classic and wifi switch with motor backup. Then after I have a few flights under my belt make the final decision on what I want to do and buy the additional hardware.
Click to expand...

The cost of the wifi switch is why I suggested a screw switch. They're a couple of bucks from Missileworks (and probably other sources) and extremely reliable. You just need a large enough hole in the airframe to slip a small screwdriver into at the pad. If the TRS does everything you need for less, that might be easier.
 
Agree with focusing on GPS or some other tracker first. I’ve seen more rockets lost because they can’t find them than failed deployment.

And if you want super portable solution for your Eggfinder TX check out the Labrat sleds. I attach them to the shock cord and it’s easy to swap rockets. Also does a fantastic job protecting the tracker.
 
cerving said:
My take on this is that about 99% of the deployment failures that I've seen are mechanical... including batteries moving around and the connectors coming undone. Secure everything so that nothing can move and your deployment controllers will be fine, and yes, put the GPS in the nose with its own battery.
Click to expand...
This is what my gut tells me too. Obviously I have no experience with electronic deployment in rocketry but that just makes sense. Fewer components means less things to fail.
 
RE: beginning with a GPS tracker first...

I completely understand where you guys are coming from and I agree. Just from my own anecdotal observations more rockets seem to be lost than damaged from improper deployment.

However, I think there is another way to manage the risk of losing the rocket, keep the altitude low. That is exactly what I plan to do with mine as I progress thru the three steps I outlined above. This is about learning and gaining experience, not setting altitude records. I'll keep it under 1500-2000', even for the first GPS flight just to be sure everything works. Once I've got this all under my belt then I'll push the envelope on motor size. I have considered doing my L2 cert on a L1090. Also, GPS tracking requires more electronics because I need a ground station. So it's easier to build just a single altimeter and work on electronic deployment than to step into GPS. At least that's how it seems to me.
 
Last edited:
Alright, prepping to build the Eggtimer Classic. I bought a Hakko FX-888D soldering station and a Hakko 1.2mm beveled tip. I couldn't find a 0.8mm conical tip that didn't have 2 weeks shipping and many people commented this tip worked well for both thru hole and SMD components. I'll give it a try on the practice boards I ordered and if I have difficulty then consider trying the 0.8 mm conical tip before assembling the Eggtimer.
 
Ok, I've settled on the electronics hardware. I am going with an Eggtimer Classic plus wifi switch and the Eggtimer TRS. Order has been placed for the things I didn't already have so now it's on to batteries...

I'm trying to keep it simple. If I've read all the instructions correctly then all I need are two batteries - one connected to the wifi switch which will output power to the classic and another connected to the TRS powering the computer, tracker and deployment. For batteries I'm looking at two Turnigy 500 mAh 2S 20C Lipos, one for each device. That should give me ample deployment current and enough power to run the electronics for at least 4 hours. Any reason these batteries will not work?
 
Last edited:

Similar threads

C
Permanently Installed AV Bay?
Replies
12
Views
557
conneryc
conneryc
gldknght
Avionics Bay and Pull-pin switch Question
Replies
25
Views
2K
DaHabes
DaHabes
DaHabes
Sold AV-Bay Kits and Altimeters for Sale
Replies
2
Views
307
cbrarick
cbrarick
cerving
IMPORTANT Firmware Update for the Eggtimer Quantum, Proton, and Quasar
Replies
23
Views
1K
NTP2
NTP2
W
Happy New Member of the "Eggtimer Club"
Replies
1
Views
703
waltr
W

Latest posts

Back
Top