Power:
An external battery and a switch are required. The Raven can be powered by any DC
power source between 3.8 and 16 V. 9V batteries and single LiPoly cells of 165 mAhrs
or less are the most common choices. An aerogel ultracapacitor will keep the altimeter
operational when the power is disconnected for 7-10 seconds, so a separate deployment
battery is not required. If one is desired, one up to 20V can be connected through the
deployment charges while a lower-voltage battery is used for the electronics via the +In
and Gnd pins. Please carefully note the battery polarity before connecting it. Although
the Raven4 has reverse battery protection, connecting a large battery in reverse could
permanantely damage the altimeter.
The field-effect transistor (FET) used to switch the Apogee and Main deployment outputs
is rated for 22 Amps for pulses <= 1 second, and has a resistance of about 11 mOhms. .
The largest lithium polymer battery that should be used with the Raven is 1S, 300 mAhrs,
because larger lipo batteries can produce currents well in excess of the 22 Amp rating of
the deployment channels in the event of an output short circuit, which can permanently
damage the altimeter. Motor airstarts typically result in short circuits as soon as the
motor ignites, so be sure to use batteries for airstarts that cannot exceed the FET rated
current when shorted.
Any external switch can be used as long as it can handle the deployment charge current.
Our customers love the Featherweight screw switch because of its reliability, tiny size,
and convenient mounting terminals. The screw head wipes and preloads the contacts
with every operation. The Featherweight magnetic switch is also a great option as no
holes or alignment are required to use it, and its solid-state construction makes it very
reliable.
High G flights:
For extra durability, a dab of epoxy or silicone can be used under the Raven’s hold-up
capacitor to secure it to the board. The hold-up capacitor is the component wrapped in
shiny black plastic next to the USB connector.
Operation in the Field
Although the Raven is designed as an advanced recording altimeter, it can be installed
and used indefinitely without ever being connected to a computer, using the default
settings for the outputs. The following describes how the Raven is operated at the launch
range.
Pre-flight operation
Turn on the Raven using an external arm switch. The first set of beeps after power-up is
the battery voltage, rounded down to the nearest volt. (9.7 Volts = 9 beeps). After
power-on, the Raven goes into pre-launch mode. The Raven will beep a low, single beep
every 2 seconds if no charges are detected or if the accelerometer does not read a near-
vertical orientation. In the case of the Raven3, the single beep will also happen if the
battery voltage is below 3.85V. The Raven will emit a high beep for each channel that is
connected and has a voltage applied. The Raven beeps once for each channel, and
indicates the continuity for each channel by giving a high beep for channels with high
continuity voltage, and a single beep for channels without a charge connected. The blue
