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Bluetooth MARSA
#11
(01-19-2012, 02:47 PM)jderimig link Wrote:I agree electronic arming would be cool.  However I have not figured out a way to do that economically that doesn't violate the NAR disarming rule.  I am not sure of the TRA requirement.

NAR says there must be a means of physically disconnecting the output devices from the power source.  In my opinion software disconnect (Telementrum) or semiconductor disconnect (Featherweight mag switch) doesn't meet the bar of this requirement because power is always connected.

Only if it is the sole means of isolation.  I used a combination of physical and software switches on the TeleMetrum.  Physically disarmed until on the rail, armed via software when the rail was vertical.  In case that STILL was not enough to satisfy the requirement - I added switches to the charge circuits as well.  What about using a relay to arm?  WOuld that meet the requirement?  More costly to be sure, but would it meet the physical disconnection requirement?

Nat - I didn't have a smartphone either.  I did order one today though after reading this thread.  ;D

Dale
Dale Stoyer - L3
NAR #91256
TRA #13499
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#12
Android OS I hope....
John Derimiggio
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#13
2. Option 2.  - I'm into the MARSA4 for the features and not so much for the interface as I set it up the night before and check it the night after the launch. 

What about bluetooth communication to actuate charges from a remotely located altimeter.  Put the charges wherever you want and not worry about wires.  (your idea - I think)

Will it work with a blackberry?
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#14
(01-19-2012, 04:57 PM)jderimig link Wrote:Android OS I hope....

Of course.  Now when can I get one of these beauties! ;D

(01-19-2012, 02:47 PM)jderimig link Wrote:NAR says there must be a means of physically disconnecting the output devices from the power source.  In my opinion software disconnect (Telementrum) or semiconductor disconnect (Featherweight mag switch) doesn't meet the bar of this requirement because power is always connected.

To revisit this for a moment:  This, like most NAR requirements, is about safety.  I think a well implemented remote arming method is actually SAFER then standing on a ladder and flipping a switch to arm the charges.  I would much rather be 10ft or 10 yards away when it arms instead of 10 inches.  I believe a case can (and should) be made to ammend the NAR requirements to allow (and even encourage) remote arming of charges.  Perhaps a demonstration of such technology at NSL to Trip Barber would be in order?  Only problem is there is nothing I have seen that would qualify.  Unless you get busy, John...

Just sayin'

Dale
Dale Stoyer - L3
NAR #91256
TRA #13499
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#15
(01-19-2012, 11:49 PM)Jeff Taylor link Wrote:What about bluetooth communication to actuate charges from a remotely located altimeter.  Put the charges wherever you want and not worry about wires.  (your idea - I think)

Possible but probably not right off the bat as the market for that is smaller.  Might be easier to do that with current MARSA's with a remote/slave plugin on the expansion connector.

Quote:Will it work with a blackberry?

Not likely.  Market is smaller and RIM is circling the drain.
John Derimiggio
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#16
(01-20-2012, 09:29 AM)Dale Stoyer link Wrote:I think a well implemented remote arming method is actually SAFER then standing on a ladder and flipping a switch to arm the charges.  Dale

Dale, I agree with you, probably more injuries are ladder related than arming related.

Its hard to beat the theory of a mechanical power interruption with a case for fail safe electronic arming.

A servo actuated power switch would work but that would be relatively expensive (parts cost of $50).

I think turning on the altimeter when the rocket is horizontal and starting launch detect mode remotely fits the NAR rule (although I would make it not legal for airstart configured electronics).  I think a mechanical power kill switch is here to stay and probably rightly so.
John Derimiggio
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#17
Yes, remember that mechanical relays can lock on (burnt contacts) or bounce if jostled enough. Ask us how we know  Wink
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#18
Seems to me that there is value in the first option because you could have real-time telemetry, which is a lot more expensive right now than $250.

However the second option of a smaller separate unit also has value because it is more universal, especially if it can be equipped with a USB port to connect to another altimeter. I think it would conceivably have more mass appeal, because it could connect to a lot of different altimeters.

Plus, the MARSA altimeter as it is now, is at best a very tight fit in a 2.26" dia. tube. Great for larger rockets but not so great for minimum diameter ones. If you made a smaller unit that connected to a smaller altimeter, you could reduce wind resistance by eliminating the need for an external switch or allow the builder to place the physical switch inside the airframe instead of outside. Someone building a Wildman Blackhawk 38 would love this combination.

I would also be interested in a GPS unit that could enable me to track my rocket with a smartphone via Google Earth.
Evan Brown
NAR# 92851
Level 2
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