Today, Chris Mancuso, and myself (Rizwan Merchant) accompanied Mr. Darby from the Electrical Engineering Department of ULL to give a presentation to The Louisiana School for Math, Science & the Arts, located in Natchitoches, Louisiana. The topic of the presentation was CAPE and the other student projects in the Electrical Engineering Department.  Below are a few photos we took of the presentation.

Well yesterday, January 16th, 2009, we tested the parachute for Balloon 2. Our first test used a can of dried up cement. Photos Below:

On top of the building before throwing out the parachute.

The Parachute has been deployed…

and lands safely!

After the initial test,  our general consensus was the parachute did not have a heavy enough package, and didn’t deploy quick enough. So to remedy this,  we took a coke can, and filled it with gravel and repeated the test again.

Photos Below:

Chris gets ready for the second trial.

and down it comes, more efficently, and deploys quicker.

Balloon 2 is on a tight schedule. We’re launching the 31st of January, and not everything is put together yet. Because of this, vital systems are being pushed for completion first. Still, others are hard at work with sensors and data collection tools, trying to get them ready in time as well.

As for Sensors – Joseph has been working on trying to get the temperature and pressure sensors up. The on board temperature sensor is working great now, and he’s been busy getting the external temperature sensor and a pressure sensor on-line.

Here’s a shot of the external temperature sensor board. It’s an i2c based Maxim 6633 – the same chip as the internal sensor. The header is carrying i2c clock and data signals, as well as power and ground.

This is our pressure sensor. It’s an analog device, so it’s plugged into a header that interfaces with the PIC’s ADC (Analog to Digital Converter).

Jeremy and Nick have also been working a good bit on getting the cameras up and taking pictures/video with remote commands. It’s starting to look good, and they have a board wired up and are currently testing. They are using a 2222n transistor and raising TTL logic line high on the PIC that is connected to the Base pin of the transistor. This allows current to flow from the Collector to the Emitter, simulating a button push to either turn on the camera, or start recording video. Here’s a shot of the test setup.

It’s coming along great, and everything is on track for a January 31st launch. Here’s one last picture – the board powered up and transmitting a basic location beacon:

Nick designed into Balloon 2′s board a handy feature – a jumper that disconnects power from the batteries to the board when open. This would allow us to package the balloon and only plug in a jumper when ready to launch. While nice, we were a bit concerned about still messing around with the internals of the balloon minutes before launch. To make launching easier and less of a hassle, a small SPST (Single Pole Single Throw) Switch was purchased from radio shack, and wired up to a small pcb, along with a power LED.

This allows us to completley seal the box, and simply throw a switch before launch.

It’s a simple circuit. The switch connects the two pins of the jumper when thrown and leaves them open when switched off. The led draws power from the jumper’s circuit when powered on. There was no ground locally available though, so an extra header pin was required to bring in a common ground from the board. A 160 ohm resistor was used to protect the LED from the high current coming straight from the board.

To calculate resistor values for an LED in a circuit, we can use Ohm’s Law.

It states that:

V = I * R

Where V = voltage, I = current, and R = resistance.

Since we’re solving to find a resistor value, a little algebra manipulates the equation into R = V / I. Now we can just plug in the values and solve for R! If the LED specification is unknown, generally safe values to use are 2V at .02A. Since we want 2V, and our circuit is providing 5, we subtract 2 from 5 to get 3 – the voltage drop we want to accomplish with our resistor. Now our equation is:

R = (5 – 2) / .02

Where R = 150. Since all we had in the lab were 160 ohm, I used one of those. It doesn’t hurt to use a higher resistance, it will just shine a little less bright. Wire it in series with the power, or ground of your LED. Either one is fine, and everything should work!

We are now in the final stages of development for CAPE’s second balloon project. The PCB and circuitry have already been developed. It’s now down to final software testing/integration and structure build.

Today was the second work day, and we accomplished alot yesterday and today. We were able to get the temperature sensors up and running, finalize the On Board Computer (OBC) code, and we saw GPS data transmitted from the board to the ground station over the air. We started building the outer housing, and cut some styrofoam to fit. We even took a few test pictures, and the cameras are working perfect.

For the outer structure itself, a sturdy cardboard box has been chosen. We’re using 1in. thick Powerfoam Insulation cut to size to insulate the interior of the box.

There was styrofoam everywhere..

A few measurements were taken, and the backing of the foam was cut using a utility blade.

Here’s a completed picture of the bottom insulation cut to size, with a hole for the earth-facing camera.