Mixing Altimeters

[Steve JensenParticipant]

I have a Raven and a PerfectFlite WD for deployment. I wanted to use two on the same sled within close proximity for redundancy.

Is there an interference issue? Seems like a cool set up — both velocity and barometric based.

Anyone else used this pairing?

[Warren B. MusselmanModerator]

I usually use different altimeters. Perfectflight MAWD or HiAlt45 plus a Missileworks RRC2X or mini-RRC – I’ve even flown Adrian’s 1st generation altimeter – the Parrot along with 2 others. Never a problem with that.

On the other hand, altimeters in close proximity to transmitters are definitely problematic. Typically I put flight avionics in the coupler and tracking beacons or GPS telemetry in the nose.

Warren

[AdrianParticipant]

I don’t think that electrical interference will be a problem. I haven’t found a case yet in which there is any discernible effect on the Raven from a transmitter or other electronics. Having a beeline transmitter in close proximity to to a Raven does not affect the baro data like it did for the Parrot altimeter.

Some people are concerned about making sure that 2 charges don’t go off at the same time in the same tube. If you want to avoid that, you can put a delay on the Raven’s deployment charge for apogee, and use a different altitude setting for the two altimeters for the main deployment.

[Steve JensenParticipant]

That has kept me from using two Perfectflites!

The Raven is more adjustable. I expect you could use two Ravens in tandem.

Being able to adjust the apogee charge is a really cool benefit to the Raven.

[AdrianParticipant]

Thanks. You can also use a single Raven, with its four default output settings, to do both primary deployments and both backups with one altimeter. The default apogee output is accelerometer-based, and the default 3rd output is set up to use a baro-based backup with a delay. The 4th output is set up to deploy at altitude, with a delay. This setup makes a setup single-fault-tolerant to most (but not all) faults. You would be covered for a bad ematch, dud charge, output wiring failure, or a sensor failure. You still need the battery that powers the logic, and the microcontroller, to work.

[John A. WilkeParticipant]

Some people are concerned about making sure that 2 charges don’t go off at the same time in the same tube.

I often use one charge if I’m using two altimeters. If your systems fail (batteries or altimeters or ematches or whatever), that is one thing. If you got your powder from the same source, it is either good or it is bad. If it is GOOD, the 2nd altimeter will light it. If it is bad, neither will light it.

If you did wire two separate charges from 2 different altimeters, the odds of them detected the agogee to the millisecond are pretty remote anyway. There have been a lot of articles written on that. You’d probably be fine…

[SCOTT EVANS]

I have used 2 RRC Minis. I set the back up with a delay of 2 or 3 seconds at apogee and the back up on main chute at 3 to 500 feet lower than the primary atimeter. 2 switches 2 Batteries 2 altimeters 2 pairs of charges. Total redundancy. I wondering about the room in the ebay in that Kestrel. 🙄

[John A. WilkeParticipant]

I have used 2 RRC Minis. I set the back up with a delay of 2 or 3 seconds at apogee and the back up on main chute at 3 to 500 feet lower than the primary atimeter. 2 switches 2 Batteries 2 altimeters 2 pairs of charges. Total redundancy. I wondering about the room in the ebay in that Kestrel. 🙄

Plenty of room!! gosh, I’m not used to having so much room. I feel like I could stuff a loaf of bread in there! I think you could probably squeeze between 75 and 100 Ravens in there 😀

If you need more room, I’ll get you a longer coupler and a longer fwd section. Try it out first, I think you will be fine.

The ebays for those 24mm, 29mm, and 38mm rockets can be tough. I felt like I was trying to jam a sparrow’s nest into the last 24mm that I did.

[SCOTT EVANS]

I have used 2 RRC Minis. I set the back up with a delay of 2 or 3 seconds at apogee and the back up on main chute at 3 to 500 feet lower than the primary atimeter. 2 switches 2 Batteries 2 altimeters 2 pairs of charges. Total redundancy. I wondering about the room in the ebay in that Kestrel. 🙄

Plenty of room!! gosh, I’m not used to having so much room. I feel like I could stuff a loaf of bread in there! I think you could probably squeeze between 75 and 100 Ravens in there 😀

If you need more room, I’ll get you a longer coupler and a longer fwd section. Try it out first, I think you will be fine.

The ebays for those 24mm, 29mm, and 38mm rockets can be tough. I felt like I was trying to jam a sparrow’s nest into the last 24mm that I did.

For 2 ??
What size powder charge you using. I will give you a dollar if you do the ground test. 😉 I thought I would use 3 pins.

[AdrianParticipant]

For 2 ??
What size powder charge you using. I will give you a dollar if you do the ground test. 😉 I thought I would use 3 pins.

When you use small altimeters and batteries, you might be surprised how much you can pack into a small space. This 38mm av-bay has 2 Parrot altimeters, 2 batteries, 4 screw switches, and a transmitter:

http://www.rocketryplanet.com/forums/showthread.php?t=2409

It’s about 3″ long.

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