[AR] Re: magnetic apogee sensor
- From: "David W. Schultz" <david.schultz@xxxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Sat, 18 Jul 2015 13:09:55 -0500
On 07/18/2015 12:11 PM, John Dom wrote:
As far as I am slowly finding out, barometric, accelerometric or even
such 3D sensors record or transmit trajectory data like apogee which
are only useful for post-flight analysis. Giving nice graphs to point
out when apogee occurred in time, later on. But AFAIK, they are not
actuators which can fire the squib near apogee time. Most rocketeers
I know, familiar with nineties prints and code like RDAS report nice
altimeter graphs. But their parachute squib is fired by... a timer!
Apogee time preset by trajectory simulation software. Reliable?
The RDAS, AltAcc, (I bought my first AltAcc in 1999.) and many other
altimeters use the sensor data to determine the time to activate the
outputs. In the case of the two mentioned, acceleration is integrated to
find apogee while a pressure sensor is used to deploy a main parachute
at lower altitudes.
Magnetic sensors will never be apogee sensors. They are instead attitude
sensors and in the case of the original, not very good at that.
The original magnetic apogee detector compared the output voltage from
an analog magnetic sensor to a reference voltage to trigger the output.
It required that you adjust that reference voltage prior to flight by
rotating the rocket to the desired angle and turning a variable resistor.
This is complicated by the fact that the magnetic field is not aligned
perfectly horizontal so the actual attitude at deployment depended on
the direction of flight.
To use one of the more modern magnetic sensors with integrated ADC you
will have to add a micro-controller, output switch, and code.
--
David W. Schultz
http://home.earthlink.net/~david.schultz
Returned for Regrooving
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