The Olympus Project: Part 35 “Using the Olympus Electronic Payload”

When you are ready to use your altimeter in an Olympus flight, the following steps are recommended. You can use this as a baseline for developing your own checklists for all four stages of the flight.

Preflight

• Determine which microSD card will be used for flight. It is recommended that a blank card be used and that you format the card prior to use. Place it into a computer to check for errors.
• You may wish to rename the card to something that make sense for the mission. This may include a flight date, project name, session number, etc.
• Charge the battery. This will help ensure that you have plenty of battery power should you find your rocket and payload sitting on the pad for an extended period of time.
• Do a preflight test on the payload. Insert a microSD card and turn on the system. Move the payload bay around and then turn the system off. Remove the card and insert it into a computer and read the data. This will help ensure everything is working properly before heading to the pad.
• Place clear payload bay over the electronic payload. Secure to payload base using tape. Do not cover vent holes located near bottom of the payload bay.

At the Launch Pad

• Insert the flight ready microSD card into the payload bay.
• Connect the two battery clips to power on the system. The status lamp should turn green to indicate the system is functioning as expected. If you get a color other than green, it indicates an error in the system. Error messages include:
  • Flashing Red – microSD Card Module error.
    Check that a card has been inserted into the holder. If a card is present remove and reinsert. If you still get a flashing red lamp, try a different card. If still getting a flashing red lamp, check for loose connections
  • Flashing Yellow – MPU6050 error.
    Check for loose connections
  • Flashing Blue – BMP180 error.
    Check for loose connections
  • Steady Blue – File Write error
    This indicates that there was an issue while attempting to write data to the microSD card. This error will attempt to self-correct by resetting the microSD card module. If it does not reset check the microSD card and replace.
• If payload appears to be working properly, attach nose cone to payload bay and secure with tape.

During Flight

• Observe the flight of the rocket so that it can be recovered successfully
  • You may want to use multiple observers. If the payload bay were to separate from the rocket one observer can track the payload bay while the second observer tracks the rocket.
• Track payload bay to landing site. Upon arriving on the landing site, remove the tape from the nose cone and remove the nose cone from the payload bay.
• Disconnect the battery from the payload to turn off the payload
• Observe the overall condition of the payload. It anything appears missing, you may want to search the local area.

Post Flight

Upon returning to the flight preparation area

• Remove the payload bay tubing from the payload
• Remove the microSD card from the payload.
• Insert the microSD card into a computer. Confirm that there are data files on the card. Copy data files from microSD card onto the local computer
  • During the appropriate time, perform analysis on the data collected
• Check the rocket and payload. Make note of any damage or missing components. Depending on any damage that has occurred, make a determination
  • on whether it is safe to continue flying in the current condition
  • to repair the rocket on site and attempt to fly again
  • if the rocket will need extensive repairs offsite in order to fly again
  • if the rocket has sustained major damage and is no longer in a repairable condition
• Make any notes and observations that may be appropriate for the mission/project.

The Olympus Project: Part 34 “Final Assembly”

With everything soldered in place, it is time to start the final assembly of the avionics bay.

The Battery

The first component to be installed is the battery. The battery has two sets of wires coming from it. The charging cable has a 3-pin connector and is attached to the shorter wire set, while the power cable has a 2-pin connector but contains the longer set of wires.

When inserting the battery, both connectors will not fit through the opening at the same time. Begin by inserting the charging cable and make sure it is completely through the opening.

Next insert the power cable through the opening. Once both cables and connectors are through the opening, push the battery forward into the avionics bay.

Nano & microSD Card Module Placement

The final assembly process begins by connecting the microSD card module to the Nano. With the two connected, begin to insert the entire assembly into the A-PAM housing. In the picture below you can see where the microSD module has been slid forward, with the Nano about halfway into the A-PAM housing. The sensor housing is to the rear as the cable lengths allow it to move out of the way while working on the A-PAM components. You can also see the battery cables are extended fully through the front of the housing.

Continue to move the Nano and the microSD card module forward until the USB connection of the Nano is completely within the opening. The front of the microSD board should be flush against the inside of the forward bulkhead. The LED status lamp should slid into position along with the Nano. When moving this assembly take your time, making sure the LED lamp and the Nano both move forward at the same time.

Attaching the Sensor Housing

With all of the components secured in the A-PAM housing, it is time to attach the sensor package. The picture below shows the two components being lined up. You will need to work the wires into the sensor housing as you bring the two housing together. Once lined up insert two screws to secure the two housing together.

Attach the Payload Adapter

The final part that needs to be attached is the Payload Adapter. There are two screws that attach it to sensor housing. Make sure that these screws are secure, as this is what attaches the entire payload assembly to the recovery system. The picture to the right shows the completed assembly.

This completes the assembly of the avionics package for the Olympus Project.

The Olympus Project: Part 33 “More Electronics Installation”

Installing the LED Status Lamp

The last component to install is the LED status lamp. Fortunately, all of the pins used for the lamp are on the same side of the Nano board and pretty close together. Unfortunately the lamp is located on the side between the two plastic mounting rails for the Nano and the microSD card. This does not leave much working room.

I knew early on that we wouldn’t be using any extra wire for these connections. Except for the wire that connects to the common ground, this is true. The first thing we did was solder the 220Ω resistors to each of the red, blue and green pins on the LED. I cut the pins on the LED short, as I knew there was a limited amount of space to work with. I also want the wires from the resistors to fold back to reach the connections on the Nano. The picture on the right shows this part of the assembly. The resistors are soldered in place and the wires are bent into the approximate position on the Nano. The ground wire has not been soldered into place at this point.

When the Nano board is inserted into the avionics bay, the board comes all the way to the forward bulkhead. I knew that the lip around the LED lamp would end at the bulkhead as well. Line up the LED lip with the end of the Nano board and then routed the resistor wires to the appropriate connections on the Nano. However, at this stage I was not ready to solder these wires in place. I needed to make sure the assembly would fit inside the avionics bay.

Carefully insert the Nano and LED assembly into the avionics bay. With both pieces in their proper position, the resistor wires were bent over to hold them in place. Both pieces were carefully removed and the wires soldered in place.

In the picture on the right you can see the other connections are already in place. With the clamps holding everything in place we can solder the status lamp to the Nano and then trim off the excess wire.

Before you move on to the final assembly, check your system to make sure everything is working as expected. It is important to test your components and assemblies as you go along. It makes it much easier to detect and troubleshoot issues when they occur.

The Olympus Project: Part 31 “Beginning the Electronics Installation Process”

With the avionics and sensor housings printed, it is time to wire the components together. This takes some planning and patience as you are working in tight quarters. However, it is possible to get everything installed with room to spare.

The graphic on the right shows the connections needed for the avionics package. The LED lamp requires four connections, while the microSD card module requires six (including a common ground with the LED and card module). The two sensors both require I2C connections and the BMP180 needs a 3.3 volt power supply. To complete the wiring is the VIN and ground connection coming from the battery to the Nano.

I was able to determine pretty quickly that soldering the wires to the top of the Nano was going to cause issues. Instead, the wires come up from the bottom and are soldered into place.

The next item that became readily apparent is that the components would need to be soldered in place first and then installed in the avionics bay. Trying to solder next to the plastic avionics bay was not going to end well.

Wiring the Components

There is no single method to installing the connections on the avionics package. You can do it in any order you think will work best for you. The order that I present here is just one method, but not the only method.

Installing the MicroSD Card Module

I gave considerable thought on how to attach the microSD card module to the Nano. The connections on the Nano are along the sides of the board, while the card module has pin connections that are at the rear of the board. While I did give some thought to removing the pins and soldering the wires directly to the board, in the end I decided to make use of the pins. The use of the pins actually seems to make the assembly easier.

In the picture on the right you can see five of the six microSD card module wires routed to the rear of the Nano (the others wires seen include the I2C connections, power and ground wires and the 3.3 volt connection for the BMP180).

Note: To help identify the 3.3 volt power line, it was marked with black stripes using a permanent marker.

The microSD card connection wires use a single six slot DuPont connector at the end. The wires are long enough to curl around and reach the pins of the card module.

The picture on the left shows the card module wires inserted into a six slot DuPont connector. The other end of the wires are soldered to the underside of the Nano and exit to the rear.

Before you install the Nano board into the avionics housing, you need to complete all of the soldering connections.

The Olympus Project: Part 30 “3D Printing the Housings”

The stl files were exported individually from Tinkercad and then imported in Cura 5.2.1. When printing these parts I used a 0.2mm layer height and 2-wall construction. Supports were necessary for the sensor housing and the A-PAM housing. Supports are optional on the base. Infill was set to 12% for all three parts.

Printing the Housings

Both housings and the payload base was printed on an End 3 V2 printer. I have been using Hatchbox 1.75mm filament and it has worked well for me. The A-PAM and Sensor housings were printed in a bright orange color for high visibility in case it separates from the rocket. The payload base was printed in silver to match the rocket’s color scheme

I did add four custom support cylinders to help bridge the gap in the A-PAM and Sensor housings. Each support tube was just 2mm in diameter. For me, this arrangement seemed to work slightly better than using just two 4mm supports on each side. We also used the support tubes on the payload base were the screw holes are located. As with most projects like this, you may wish to try both. Results can vary from printer to printer so use the settings that work best for you.

Note: Since this project was completed, Cura has released an updated version that now includes tree supports. In some of our initial prints using the tree supports on the overhang sections of the prints seem to be much better in quality. This can be seen in the picture of a test print using the new tree supports option.

With the 3D prints now completed, it was time to assemble the electronics into our avionics bay. We will start that process in our next Olympus post.