■ The schematic of the NearSpace UltraLight.
opening the airframe. There are two additional LEDs on
the airframe. These indicate when the GPS has a lock and
when the flight computer is transmitting a position report.
It’s more convenient if the flight computer’s I/O
provides not only access to the PICAXE, but also provides
power to all experiments plugged into them. The
UltraLight uses the three-pin servo standard for all its I/O
■ The back of this DB- 9 has solder cups that allow wires
to be soldered directly to the connector.
68 January 2011
channels. Therefore, each channel in the I/O has a
connection directly to the PICAXE, + 5 volts, and ground.
The I/O channels on the UltraLight are grouped into
four ports based on their function. First, there’s the Analog
Port of four channels. The Analog Port digitizes sensor
voltages with a precision of either eight or 10 bits. The
second port is the Digital Port with its three channels.
This is where sensors that produce ON/OFF signals connect
to the flight computer. A good example is the Geiger counter;
it produces a pulse (0 to 5 volts) upon the detection of a
cosmic ray. The third port is the Servo Port. It controls the
positions of two servos. Servos are useful in near space to
position experiments, like cameras, and to release dropsondes.
The final port (and different from the others) is the
Camera Port which operates the shutters of two cameras.
The Camera Port can control two different styles of
cameras. First are the traditional cameras with modified
shutters. These are cameras in which a cable has bypassed
the camera’s shutter button. Once bypassed, the cameras
depend on the flight computer’s relays to trigger their
shutters. Alternatively, if a camera’s power switch has also
been bypassed, the two channels of the Camera Port can
power on and off a camera and trigger its shutter.
The second type of camera that the UltraLight can
operate is a Canon camera running the USB remote.