Playing with Surface Mount Shift Registers

I’ve been playing for a while with making my own circuit boards with OSH Park. Usually these are reasonably large two sided boards and they typically cost me $8-$25 each. But OSH Park doesn’t have a setup fee or minimum board size. So I decided to see how small of a circuit board I could make.

A bunch of surface mount LEDs sitting on a tiny PCB.

The result is a really simple board that’s pretty fun to solder. The boards came out to something like $2 each, and the parts, not including connectors, were about as cheap (connectors are pricey! This was a surprise for me).

If you couldn’t guess, each PCB is just a breakout board for a 595 surface mount shift register mounted on the backside of the board. Each output pin of the shift register is tied to an LED with an inline resistor.

Here’s a video of these boards being driven by an arduino:

All in all, a really cheap and easy project.

 

BMP085 Pressure Sensor at High Altitude

Tim, Alex, and I launched a balloon in September of last year. On it, we flew an IR camera, pressure sensor, and a GPS on an Arduino and an APRS tracker.

An IR photograph taken from about 85,000 feet.

The sensors and Arduino getting ready for flight

With this sensor configuration, we were able to get GPS data from above 60,000 feet (at which GPS usually shuts off), and compare this with the pressure sensor we were flying, a BMP085 we bought from sparkfun. The datasheet for this sensor states that it’s rated for pressures as low as 30000 Pascals, or about 30,000 feet above sea level.

Pressure vs. Altitude

However, it seems that it worked for higher altitudes, too. At the highest altitude we reached, 26898 meters, the BMP085 recorded a pressure of 1781 Pa, or about 27350 meters above sea level.  So it seems that the BMP085 works at altitudes above 30,000 feet, just not as accurately.