RavenPlus All-in-one Altimeter

[troj]

The mini-maTch connectors are a new variety that is compact and has some good features for vibration resistance, but the rated current per contact is pretty low. I'm not sure how available the board-to-board variety is.

That's one of the things I was wondering -- how much power can they handle?

Could a multi-contact approach be used where each output uses multiple contacts on the board-to-board connector?

-Kevin

 

[Adrian A]

That's one of the things I was wondering -- how much power can they handle?

Could a multi-contact approach be used where each output uses multiple contacts on the board-to-board connector?

-Kevin

Yes, that's possible. It could be a lot of contacts, though. I expect that the connector would work for 1 second with current much higher than the 1A spec value. But how many contacts I would need for 20-30 Amps for 1 second is tough to guess. 2-3? 8? More than 2-3 per output would be tough to accommodate.

 

[troj]

Yes, that's possible. It could be a lot of contacts, though. I expect that the connector would work for 1 second with current much higher than the 1A spec value. But how many contacts I would need for 20-30 Amps for 1 second is tough to guess. 2-3? 8? More than 2-3 per output would be tough to accommodate.

There's where I have zero clue - I know enough about electronics to be dangerous. And that's on a good day, after I stay in a Holiday Inn Express!

-Kevin

 

[H_Rocket]

But how many contacts I would need for 20-30 Amps for 1 second is tough to guess. 2-3? 8? More than 2-3 per output would be tough to accommodate.

Why would it be difficult, just buss them all together with a big solid pad on the board?

Couple of families I would consider are:

Metrimate by AMP

Mini-Mate-n-Lok by AMP

One option would be a board to board connection using mixed contacts D-subminiature. Though that one would likely be cost prohibitive.

I can't find any reference to the mini match connectors. Could you provide a pointer?

 

[Adrian A]

Micro-match spec:

https://www.te.com/commerce/Documen...9052FpdfEnglishENG_SS_108-19052_F.pdfN-A

Digikey search will work.

To keep cost and size down, I would want to limit the connector to one 0.8" long connector at each end, and ideally around 0.3" stack height to restrain the battery under the board.

 

[Adrian A]

I have the new rev of the PCBs back from the board house for all the Featherweight magnet-sensing products. I'll be assembling and testing them this weekend. I think I fixed the problems in all the designs from last time, so unless I screwed up, all of the designs are production-ready. The RavenPlus design I'll be testing has an 8-position screw terminal at one end for the 4 outputs, and it uses 3 of the 4 mounting screw holes to sandwich and connect a battery adapter board under the main board. The only wiring the user would do to make an av-bay is just connecting the ematch wires to the terminals.

I've gotten the message that a tool-less altimeter swap from rocket to rocket would add a lot of value for people, so I'm still looking into that. Along those lines, here are a couple of products that could be used with a modification of the current RavenPlus design:

https://www.mcmaster.com/#knurled-nuts/=ewhf1w
https://search.digikey.com/us/en/pr...-ND/950836?wt.z_cat_cid=Dxn_US_US2011_Catlink

The latter is a screw terminal block that clamps onto the wires like usual, but it can plug and unplug from the board. It has even more current capability than the 0.1" pitch screw terminals I'm currently using. The pitch of this one is 3.5mm, so I would need to rework the board layout to put a 4-terminal version at each end. The screw/plug terminals are fairly inexpensive, so they could be left on the ends of the wire on multiple rockets.

I haven't found any high-current, compact and inexpensive board-to-board connectors yet, but I'm not done looking. Those would be used for a different concept in which a base board would be permanently attached in a rocket, and the altimeter would plug onto it.

 

[rcktnut]

I think its is a great idea to have plug in altimeter for use in multiple rockets.
What has been talked about so far though is one altimeter in a rocket right?? This also limits a person to what altimeter he has to buy, and no use of altimeters already owned, for this system anyway.

For true redundancy two altimeters should be used, right? So having the spoken about system so far, allows for only one altimeter to be pluged in.

So far in the three DD rockets I have I've been using 6 pin locking connectors with the AV bays set up to recieve the same sled.(Pic.) It is plug and go. This of course is not redundant, but will be working on that this winter, new sled and a set of altimeters. I haven't had a deployment problem yet, trusting all the links in the chain of deployment. I would feel better though having redundancy in any DD rocket that it is possible to fit in.

With larger planned projects coming up, I definately want redundancy, but will stick to 2 altimeters, differant brands, make the sled standard for all, and plug in locking connectors.


Making connector whips available would not be a bad idea, should you not find
high current board to board connectors. Also even for those not wanting to standardize the sleds to fit all, moving the altimeter from sled to sled with tool less hardware isn't so bad, a short whip/connector right out of the altimeter terminal blocks dosn't have to be fastened to the sled.

I like connectors, it at least eliminates the need for rewiring altimeter to rocket outputs, and prevents drouge/ main screw ups.

 

[rdbones]

When I am using DD system, I do not use two altimeters from the same manufacturer. If there is a fluke or flaw in one, there is a high probability that it is also in the other.

I have also built one sled that I have designed to fit in 2 different 6" diameter rockets and was easily modified to fit in a 20" diameter project.

 

[Reinhard]

I've gotten the message that a tool-less altimeter swap from rocket to rocket would add a lot of value for people, so I'm still looking into that. Along those lines, here are a couple of products that could be used with a modification of the current RavenPlus design:

https://www.mcmaster.com/#knurled-nuts/=ewhf1w
https://search.digikey.com/us/en/pr...-ND/950836?wt.z_cat_cid=Dxn_US_US2011_Catlink

The latter is a screw terminal block that clamps onto the wires like usual, but it can plug and unplug from the board. It has even more current capability than the 0.1" pitch screw terminals I'm currently using. The pitch of this one is 3.5mm, so I would need to rework the board layout to put a 4-terminal version at each end. The screw/plug terminals are fairly inexpensive, so they could be left on the ends of the wire on multiple rockets.

I own a, now OOP, altimeter that uses this kind of pluggable terminal blocks. I wrapped a cable tie around the altimeter to be sure it couldn't come loose, but I believe this was overkill. I've never heard of problems regarding the connectors.
Another solution that was used on the first generation of the Altimax is concentrating all the connections on a single SUB-D connector. This was accompanied with a mating breakout board, which was cheap enough to stay permanently mounted into the rocket.
https://www.rocketryplanet.com/content/view/2651/143/


Instead of thumb nuts, captive screw fasteners might be an option. They can't be lost in the field, but they do look expensive though.
https://www.pemnet.com/fastening_products/captive_hardware.html
https://www.pemnet.com/fastening_products/circuit_board.html

Another neat type of fastener that I've encountered were similar or identical (?) to these:
https://www.richco-inc.com/products...html?PartNum=&country=RICHCOUSA&grpcode=D1060
They work similar to removable plastic rivets with the difference that they stay permanently affixed to on part (the green "removable panel" in the linked page).

It seems to me, that there are lots of interesting parts available, labeled as some kind of "panel fastener", that make it quite easy to connect sheet like components to each other. What may be problematic, is that they often require the two parts surfaces to be in direct flush contact with each other. This can be tricky when using PCBs with components on the bottom side or when using through the hole components.

Reinhard

 

[Adrian A]

I found out tonight that the baro sensor used for the Raven (and RavenPlus) is back-ordered for 4 months. Fortunately, I have a production batch of Ravens that's almost done, so Ravens will continue to be available in the meantime. But the RavenPlus won't be available until the spring.

 

[Sampo]

Hi Adrian,

As our team is doing rather complex on-board electronics (real-time radio telemetry etc), one thing I would love to have in the new Raven is an output for real-time serial telemetry data.

The Raven already has an FTDI chip to convert serial data to USB. All that would be required is some kind of contact point to the TTL-level serial data and updating the software to send the data to the serial output during the flight. The connection might be a two-pin jumper block or even just two pads/holes on the edge of the board where you can solder wires yourself. (Once your interested in real-time flight data, you probably know how to solder.)

The MAWD currently has the option to output the flight altitude (10 or 20 times per second, IIRC) during the flight. It would be fantastic to be able to replace that with the considerably more extensive data that the Raven gathers. With some simple ASCII format it should be possible to output all of the data at least 10 times per second, probably much faster.

For our team this would be a sufficient upgrade to warrant buying the new version.

Cheers,
Sampo N.

 

[Adrian A]

Hi Adrian,

As our team is doing rather complex on-board electronics (real-time radio telemetry etc), one thing I would love to have in the new Raven is an output for real-time serial telemetry data.

The Raven already has an FTDI chip to convert serial data to USB. All that would be required is some kind of contact point to the TTL-level serial data and updating the software to send the data to the serial output during the flight. The connection might be a two-pin jumper block or even just two pads/holes on the edge of the board where you can solder wires yourself. (Once your interested in real-time flight data, you probably know how to solder.)

The MAWD currently has the option to output the flight altitude (10 or 20 times per second, IIRC) during the flight. It would be fantastic to be able to replace that with the considerably more extensive data that the Raven gathers. With some simple ASCII format it should be possible to output all of the data at least 10 times per second, probably much faster.

For our team this would be a sufficient upgrade to warrant buying the new version.

Cheers,
Sampo N.

The Raven already has the altitude available on a 3.6V pin during the flight, at 115 kbps. Processor speed limitations prevent outputting more data than that. I'm keeping the microcontroller and firmware the same for the RavenPlus.

 

[Sampo]

Hi,

The Raven already has the altitude available on a 3.6V pin during the flight, at 115 kbps. Processor speed limitations prevent outputting more data than that. I'm keeping the microcontroller and firmware the same for the RavenPlus.

What pin has the altitude info? I was unable to find this in the user's guide. This is great news and could ease our current configuration considerably.

(Currently our telemetry system is in the nose cone and we have to pull a serial line from the middle of the rocket where the MAWD is located. If we could just move the Raven to the nose cone and get the data from there it would simplify things a lot.)

Cheers,
Sampo N.

 

[Adrian A]

It's the little through-hole marked "Tx" between the micro controller and the FTDI chip. The format is what you see when you run the simulated flight.

 

[Sampo]

It's the little through-hole marked "Tx" between the micro controller and the FTDI chip. The format is what you see when you run the simulated flight.

Great, we'll have to try that out!

I'd suggest adding this info to the user's guide. I understand if you don't want to advertise soldering stuff to the board, but for advanced groups this can be a good selling point. Maybe even consider adding a female jumper connector for it to the RavenPlus?

Cheers,
Sampo N.

 

[Adrian A]

Great, we'll have to try that out!

I'd suggest adding this info to the user's guide. I understand if you don't want to advertise soldering stuff to the board, but for advanced groups this can be a good selling point. Maybe even consider adding a female jumper connector for it to the RavenPlus?

Cheers,
Sampo N.

Thanks. Let me know if you run into any snags. I'm not sure anyone has actually done that yet.

 

[Adrian A]

Considering the delay of the RavenPlus, I'm thinking about making a different product before then that would provide some of the same features but would work with existing Ravens.

How about an integrated battery mount, battery, magnetic switch, and extra deployment terminals? One question I have is whether I should have the Raven plug into it for all the terminals, or if I would leave the Raven's own deployment terminals open so that one of the two ematch wires for each output would screw down to the Raven directly as they do now. I'm leaning that way to save cost, size, and reduce electrical losses. If I go that way, I think I could keep it under $30. It would add about 1/2" to the footprint of the Raven in length and width, including the battery. I could add a USB battery charger to it for another $10 or so.

With this Raven extender, you would have 2 screw terminals for each of the 4 outputs, and the battery, battery wiring, switch and switch wiring would be taken care of. Just mount this and a raven to a sled and you're ready to connect your deployment charges and fly.

You'd save on 9V batteries and battery holders, too.

 

[troj]

At that price, I think it'd be pretty slick!

Merging this with another discussion, the battery could power the Raven for at least two hours, correct?

 

[Adrian A]

At that price, I think it'd be pretty slick!

Merging this with another discussion, the battery could power the Raven for at least two hours, correct?

I think it's around 2 hours while beeping. I should do a test on that, though, because I don't remember the results from the last time I tried it.

How much would it be worth to include a USB charger on each one? You would plug in a USB-mini cable into it to charge the battery, similar to the 38mm av-bay. A stand-alone Featherweight battery charger is available for $17, and other inexpensive alternatives are out there via the RC hobby.

Another nice thing about this is that if you have another product that runs off of a single Lipo cell, like a Tele-mini or Beeline, you could use this for that as well.

 

[troj]

I think it's around 2 hours while beeping. I should do a test on that, though, because I don't remember the results from the last time I tried it.

I'd be curious how much runtime a new battery will get, as well as one that's a bit aged.

How much would it be worth to include a USB charger on each one? You would plug in a USB-mini cable into it to charge the battery, similar to the 38mm av-bay. A stand-alone Featherweight battery charger is available for $17, and other inexpensive alternatives are out there via the RC hobby.

To me, not much, especially if it adds more than about $0.50 to the cost of the unit.

Another nice thing about this is that if you have another product that runs off of a single Lipo cell, like a Tele-mini or Beeline, you could use this for that as well.

Interesting idea!

BTW, in terms of how I would like to see it work is a header similar to what's on the av bays -- all the Raven connectors go to the board, then all the matches come off the board. I see it as simplifying wiring.

-Kevin

 

[Adrian A]

Here are the two concepts I had in mind. After a little more research, I think the one on the left won't be that much more expensive, and I think it will be more obvious how to set it up.

 

[troj]

Here are the two concepts I had in mind. After a little more research, I think the one on the left won't be that much more expensive, and I think it will be more obvious how to set it up.

Definitely, for the one on the left!

One question that comes to mind is how to retain the battery on the board, so that it does't pop loose?

The friction of the plug isn't enough for comfort, for me.

-Kevin

 

[Adrian A]

Definitely, for the one on the left!

One question that comes to mind is how to retain the battery on the board, so that it does't pop loose?

The friction of the plug isn't enough for comfort, for me.

-Kevin

Maybe an L shaped piece of wood glued onto the sled to keep the battery from moving in the high-G orientations, and tape over the top?

 

[troj]

Maybe an L shaped piece of wood glued onto the sled to keep the battery from moving in the high-G orientations, and tape over the top?

Oooh, simple!

Or, use the L-shaped piece of wood, but then have a small strap mounted with a single screw to the side. Loosen a wingnut, pivot the strap out of the way and the battery comes free. Install battery, pivot strap into place, tighten wingnut, and done!

-Kevin

 

[Adrian A]

Oooh, simple!

Or, use the L-shaped piece of wood, but then have a small strap mounted with a single screw to the side. Loosen a wingnut, pivot the strap out of the way and the battery comes free. Install battery, pivot strap into place, tighten wingnut, and done!

-Kevin

Yeah, I had something like that in mind too, but I didn't have the energy to try to explain it.

 

[GRIFFIN]

Here are the two concepts I had in mind. After a little more research, I think the one on the left won't be that much more expensive, and I think it will be more obvious how to set it up.

I like this idea as well. Like Kevin, I would like to see the one on the left. I would still be using a 9V battery (small lipo's and Cold Illinois winters do NOT get allong) So a option for a second block for a +/- connection.

 

[Adrian A]

I like this idea as well. Like Kevin, I would like to see the one on the left. I would still be using a 9V battery (small lipo's and Cold Illinois winters do NOT get allong) So a option for a second block for a +/- connection.

The magnetic sensor only is rated up to 6V, and I would rather not add more parts, size, and cost for a voltage regulator so the input could be higher, when most people will use the included battery. The Featherweight magnetic switch does have the extra parts so that it can handle up to 16V, so that's still an option.

For cold weather, I'd suggest adding another lipo and a couple of 1/2 watt resistors (about 30 Ohms) from Radio Shack, one for the heater battery and one for the altimeter battery. That plus some insulation should keep the electronics happy. I've toyed with the idea of being able to program one of the Raven's outputs to be thermostatic heater control, but I don't really have room to do that.

The Raven extender prototype works, other than the fact that I forgot to order the pin header to connect the Raven to it. Once that comes in and I check it out, I'll put up some pictures. It looks a lot like the option on the left, though.

 

[troj]

If heat is an issue, can one of those air-activated hand warmers be used? I'd imagine that they would generate enough heat to keep things warm enough inside a sealed bay.

They're cheap and easy to use, too.

-Kevin

 

[billspad]

If heat is an issue, can one of those air-activated hand warmers be used? I'd imagine that they would generate enough heat to keep things warm enough inside a sealed bay.

They're cheap and easy to use, too.

-Kevin

Does the reaction stop when they run out of air and if so is the vent hole big enough to provide enough oxygen?

 

[troj]

Does the reaction stop when they run out of air and if so is the vent hole big enough to provide enough oxygen?

Since some of them are sold with adhesive backing to be stuck to the underside of your socks and inside shoes, I'd imagine they work relatively well in a confined space.

-Kevin