Ion Chamber

NearSys is experimenting with ion chambers as an affordable radiation detector for robots and near space. The designs under experiment can be found at Charles Wenzel's website, http://techlib.com/

The electronics are soldered to a perf board and shielded with a copper pipe cap. The electronics are bolted to the can of the chamber, making the ion chamber a very durable unit.

Currently, the ion chamber under study is being read by the READADC command. to my surprise, I have determined that 5.5 MeV alphas from Americiunm-241 can be detected by the chamber but not 4.5 MeV alphas from Uranium-238

LED-based Color Detector

NearSys is testing an application based on the work of Forest Mims. In thre early 1990's. Mr. Mims published on an interesting effect, LEDs produce current when exposed to light, mosrt especially when the light has the color that the LED produces. The reason this happens is because LEDs are like little solar cells.

So after experimenting with using LEDs as a near space photometer for several years, NearSys is now experimenting with using them in a robotics application. In this case, the unit contains two different color LEDs for detecting and two fo the same color LEDs for a light source.

A two LED color detector being tested on red-colored floor

A robot controller using this unit measures the voltage produced by both LEDs to determine the color being illiminated. The best comparison seems to be made by multiplying the two values. A red and green seems to be most effective at distinguishing between colors as the graph below illustrates.

It also appears that two infrared LEDs, one 870 nm and the other 940 nm are effective at distinguishing between gloss black and flat black surfaces.

Look for a short article about this new color detector and a YouTube video in the near future.

Here's a reference for Mr. Mims' original article

Mims III, Forrest M. "Sun Photometer with Light-emitting diodes as spectrally selective detectors" Applied Optics. Vol. 31, No. 33. November 20, 1992.

Animated LED Display

The new NearSys Animated LED Display showing the number 9

NearSys is developing a animated display of 64 (8 by 8) bicolor LEDs.

The LED array is a BL-M12A883XX from Adafruit. Each square contains two LEDs, colored red and green. both LEDs can be illuminated simulataneously, so each pixel can be off, red, green, or yellow.

A PICAXE 28X2 controls the display and receives a command for the specfic display form the robot controller it is connected to.

Setting the color of each cell in a column is easy, just set two 1-byte variables (one for red and one for green). For example,
Green = 255
Red = 255

Then increment the current column to display with thess commands
Counter = Counter + 1
Column = Counter *4

Finally, set the PICAXE-28X2 output pins to acitivate all the cells in the current row.
pinsA = Row
pinsB = Red
pinsC = Green

Current, I am testing a display for a count down timer. When completed, I'll post a YouTube video.

I will write a short article on it for Servo. look for the kit to become available at around that time (January 2014).

The newest near space flight computer from NearSys is the NearSpace Simple-18. It’s a PICAXE-18M2 based datalogger in parallel with a TinyTrak 3 APRS tracker. Input/output devices, like sensors, connect to the NearSpace Simple-18 through its four ports. 1. Analog Port: used to digitize the voltages of three sensors 2. Digital Port: used to interface three digital devices or sensors 3. GPS Port: shares GPS data with both the APRS tracker and the PICAXE-18M2 4. Camera Port: used to operate two cameras Analog sensors are supplied +5 volts and ground as soon as you connect them to the Analog Port. The PICAXE-18M2 can digitize sensor voltages with either eight or ten bits of resolution. The Digital Port is a two way port. You can connect input (like sensors) or output devices to this port. An example of a digital sensor is the Geiger counter. The cameras operated by this flight computer need by-passed shutter switches. Alternatively, a single camera with a by-passed shutter and power switch can be operated through the Camera Port. The flight computer also includes a Commit Pin. This is used to prevent the flight computer from recording data prior to launch. When launch is immanent, the pin is removed, signally the PICAXE to begin collecting data. Data from the four analog and digital sensors is stored in a 24LC256 I2C memory chip. This gives the flight computer enough memory to record 256 kb of data. The chip can be replaced with a larger version if additional data storage is required. The flight computer has four LED status indicators. These indicate when the flight computer has power, when the tracker side is transmitting a position report, the status of the GPS Receiver (when its connected and when it has a satellite lock), and the current status of the flight computer. The last indicator, the status indicator is a programmable bi-color LED. The PICAXE-18M2 is programmed to illuminate the LED as desired. The NearSpace Simple-18 flight computer kit also includes a two meter antenna kit. The antenna connects to the flight computer through an SMA connector. The NearSpace Simple-18 makes a great first flight computer. It’s simple plug and fly operation makes collecting data in near space quite simple.

The Assembled NearSys GPS Simulator

NearSys LLC now sells a GPS Simulator. It allows you to test a near space APRS tracker or flight computer for its behavior during a mission. It's a way to simulate a mission on your bench top, saving you money and difficulty should something go awry.

The GPS Simulator models all the events of a GPS that's making a trip to near space. These events include GPS lock and loss of lock, launch and ascent of the balloon, balloon float, balloon burst, descent, and landing. The GPS lock can be lost at any time during the mission and can be regained at will. The ascent rate, landing speed, float altitude, and burst altitude of the mission are easy to set and vary by adjusting four well-described variables at the top of the GPS Simulator program.

This level of functionality is useful if you programmed your flight computer to respond to conditions like too slow of an ascent rate, unexpected loss of GPS lock, unplanned for neutral bouyancy, passing specific altitudes, balloon burst, approaching landing, or touchdown.

The NearSys GPS Simulator lets you test and debug these programmable features of your near space mission.

You can view the kit and its instructions at the GPS Simulator page at NearSys.com

Vacuum Cannon

What can you accelerate using a vacuum? How about a ping pong ball to several hundred miles per hour? The vacuum cannon evaculates the air from a PVC tube. Both ends of the tube are sealed using sheets of aluminized mylar and inside is a ping pong ball. After the air is evacvuated, you puncture the mylar film closest to the ping pong ball. As the air rushes back in, it creates a force on the ping pong ball. Since the air pressure is 101.3 kP and the ping pong ball has a low mass of three grams, the ball's acceleration can exceed 1,000 g's. By the time the ping pong ball reaches the end of the tube, it bursts through the other mylar film cap with a loud bang.

The kinetic energy of the ping pong ball is equal to the energy required to evacuate the PVC, minus losses due to friction and drag. Still, a ping pong ball capable of flying through an aluminum can is mightly impressive.

You can see a video of my vacuum cannon on my YouTube channel

NearSys has updated its BalloonSat Mini flight computer to version 4.0. This version is more convenient to program and to interface sensors. Rather than programming the flight computer through a serial adapter cable, the flight computer now incorporates a DB-9 connector. Interfacing sensors is easier because sensor arrays are available with simple to solder connectors that plug right into the flight computer’s I/O port.

Like the older versions, the BalloonSat Mini v4.0 also operates a camera. The flight computer can operate any electronic camera with a by-passed shutter switch. Cameras modified to work with the BalloonSat Mini v4.0 are available from NearSys.

The BalloonSat Mini v4.0 has memory to record 256 sensor readings. Since it can collect data from two sensors, the BalloonSat Mini v4.0 can record one reading per sensor per minute for the entire ascent of a typical high altitude balloon. However, it will not begin recording data until after the BalloonSat crew removes the Commit Tag.

The BalloonSat Mini v4.0 kit is available from NearSys for $23.50. The kit contains all the necessary parts except for solder. Directions for the kit and sample code are available from the NearSys website at, http://nearsys/catalog/balloonsat/mini.htm.