electronic apogee detector circuit

[THEONE]

Does anybody know any electronic apogee detector circuit ?

[dan999ification]

Does anybody know any electronic apogee detector circuit ?

 

you can buy them, do you want to make it?

 

dan.

[THEONE]

Yes i want to build it

[madmandotcom]

the easiest way to do that is by wiring a mercury switch to a capacitor, when your rocket reaches apogee and starts to drop, the centrifugal forces will cause the mercury to shift competing the circuit to the ignitor for your parachutes deployment charge

[THEONE]

The drag outside of the rocket body is better than the outside rocket body when the rocket cuts out, this will maybe enable the switch is that right ?

[dagabu]

the easiest way to do that is by wiring a mercury switch to a capacitor, when your rocket reaches apogee and starts to drop, the centrifugal forces will cause the mercury to shift competing the circuit to the ignitor for your parachutes deployment charge

 

HOLY S**T!!!! I cannot believe my ears! MMDC said something that is both correct and probably will not blow you up.... Well, except for the mercury switch and capacitor thing, the rest is OK I guess.

 

-dag

[madmandotcom]

whats wrong with the mercury switch and capacitor? it is the same thing as some of the basic estes parachute deployment devices, also, you have already agreed that the straws on rockets work

[dagabu]

Have you tried a mercury switch and capacitor to ignite a deployment device? If so then you have had the rocket zipper as the fuel is spent and the drag of the body slows the forward momentum down and the drop of mercury floats up off the bottom and blows the chute in coast phase causing the chute cord to tear down the side of the rocket destroying the body tube.

 

Try it and take video for us, you will see quickly what i mean.

 

-dag

[THEONE]

Have you tried a mercury switch and capacitor to ignite a deployment device? If so then you have had the rocket zipper as the fuel is spent and the drag of the body slows the forward momentum down and the drop of mercury floats up off the bottom and blows the chute in coast phase causing the chute cord to tear down the side of the rocket destroying the body tube.

 

Try it and take video for us, you will see quickly what i mean.

 

-dag

 

I can not understand what are you mean

[dagabu]

The drag outside of the rocket body is better than the outside rocket body when the rocket cuts out, this will maybe enable the switch is that right ?

 

YES!!! Thats what I was trying to say, thanks One.

 

This is a zipper:

 

http://www.navro.nl/img/nws/nld/nld27/nld27_46.jpg

 

-dag

Edited January 14, 2012 by dagabu

[Arthur]

IF this is for a rocket the the mercury (or equivalent!) switch is part of the answer but you need a delay to account for the coast phase before the ejection charge finally fires. This could be one second or so done in electronics or Chinese time fuse.

[THEONE]

What about Dan Pollino΄s

?

[dagabu]

IF this is for a rocket the the mercury (or equivalent!) switch is part of the answer but you need a delay to account for the coast phase before the ejection charge finally fires. This could be one second or so done in electronics or Chinese time fuse.

 

Good point, know anyone that has some time fuse?

 

Seriously, that is a a good point you but a static firing of the motor is essential to successful apogee opening.

 

-dag

[dagabu]

Brilliant! What a novel idea! That totally solves the problem.

 

-dag

[Verge]

I,m pretty sure you can use accelerometers too.Though i have little idea how to it might actually be pretty simple. Edited January 15, 2012 by Verge

[nater]

Did you check here: http://aeroconsystems.com/cart/flight-avionics/magnetic-apogee-detector/ ?

[killforfood]

The hard part is determining a coast phase profile so that the ejection charge is fired with a correct amount of delay.

An air speed trigger device can be used instead of a timing circuit but it's not 100% reliable either.

A rocket could weathercock into the wind without ever slowing down enough to fire the ejection charge.

 

http://www.nakka-roc...net/rtimer.html

 

http://www.nakka-roc...net/as-sys.html

[THEONE]

The hard part is determining a coast phase profile so that the ejection charge is fired with a correct amount of delay.

An air speed trigger device can be used instead of a timing circuit but it's not 100% reliable either.

A rocket could weathercock into the wind without ever slowing down enough to fire the ejection charge.

 

http://www.nakka-roc...net/rtimer.html

 

http://www.nakka-roc...net/as-sys.html

 

Very good idea, but were you have to put the swich ? were the air flow is better on the rocket body ?

 

Now you give me an idea, what about to use Dan Pollino΄s system but use this air switch in case of the steel balls and snap switch

When the rocket starts, the air switch will be open, cause of the high air flow , this will arm the relay... after that when the rocket΄s speed is low, the air switch will close (like Dan Pollino΄s system) and the ejection will fire...

Edited January 15, 2012 by THEONE

[THEONE]

But there is the possibility that the switch will never close, if the wind in that altitude is strong enough correct ?and maybe you will damage the air switch when the rocket falls.

 

I think Dan Pollino΄s apogee detector will by the solution...

Edited January 15, 2012 by THEONE

[Arthur]

If all you want is to bring the casing down fit to reuse then it isn't necessary to detect the apogee accurately! I fact if the 'chute deploys too high then the float will be great and the search field will be large. Fire a fuse at the end of thrust with a five second delay to 'chute deployment so that the rocket rises, coasts, and is part way down before the 'chute deploys.

 

As an alternative scheme what about a solid state barometer/ altimeter? Activated on ignition with a short (1 sec?) delay. The rate of change of altitude with time should start at a large figure and reduce as the thrust fades, reduce further as the rocket coasts and should be zero at the apogee (by definition!) However there may well be forward speed in air so there is still the risk of unzipping the body unless there is also a air speed detector (pitot tube)

 

You would need to detect dAlt/dt and look for a maximum then detect dV/dt and look for a minimum before firing.

 

However, if you reached an altitude of 10,000feet then deployed the 'chute the rocket could be 10,000 metres downwind which is a long way to walk looking for a hole in the sand (or someone's roof )

 

In the UK I have seen data logging systems for rockets -does nothing like exist in the USA? Accelerometers measure acceleration and time so the full flight can be profiled -can you determine the 'chute deployment by this means?

 

Pricewise I'd go for the time fuse option, technogeeking I'd go for the sensors and differentiators (can one hack a home weather station for the pressure sensor??)

[dagabu]

If all you want is to bring the casing down fit to reuse then it isn't necessary to detect the apogee accurately! I fact if the 'chute deploys too high then the float will be great and the search field will be large. Fire a fuse at the end of thrust with a five second delay to 'chute deployment so that the rocket rises, coasts, and is part way down before the 'chute deploys.

 

As an alternative scheme what about a solid state barometer/ altimeter? Activated on ignition with a short (1 sec?) delay. The rate of change of altitude with time should start at a large figure and reduce as the thrust fades, reduce further as the rocket coasts and should be zero at the apogee (by definition!) However there may well be forward speed in air so there is still the risk of unzipping the body unless there is also a air speed detector (pitot tube)

 

You would need to detect dAlt/dt and look for a maximum then detect dV/dt and look for a minimum before firing.

 

However, if you reached an altitude of 10,000feet then deployed the 'chute the rocket could be 10,000 metres downwind which is a long way to walk looking for a hole in the sand (or someone's roof )

 

In the UK I have seen data logging systems for rockets -does nothing like exist in the USA? Accelerometers measure acceleration and time so the full flight can be profiled -can you determine the 'chute deployment by this means?

 

Pricewise I'd go for the time fuse option, technogeeking I'd go for the sensors and differentiators (can one hack a home weather station for the pressure sensor??)

 

Sure, we have data loggers, accelerometers, altimeters and barometers galore but the actual dollar cost is pretty high unless you build it your self and then it becomes heavy and they still break all the time. Small rockets use delay in the motor, a fuse for timed delay, spring wound timers and such can be used for medium sized rockets but to launch a large rocket you do have to use robust and proven equipment that is approved for use ahead of time.

 

This exercise is really about how to make a good system for ejection on the cheap as far as I have read it.

 

-dag

[anapogeetoofar]

Honestly, I think apogee detectors are more trouble than they're worth, Just use a timer or pyrotechnic based ejection system. I do like Richards air speed switch though. I have also seen some neat LED based detectors that seem fairly reliable.

[dagabu]

Honestly, I think apogee detectors are more trouble than they're worth, Just use a timer or pyrotechnic based ejection system. I do like Richards air speed switch though. I have also seen some neat LED based detectors that seem fairly reliable.

 

And the air speed switch is easy-peasy to make.

 

-dag