Wireless Egg Drop

The wireless egg drop kit allows you to view and record data from a wireless accelerometer. The data flows through the system along this path:

  1. accelerometer
  2. small microcontroller
  3. radio transmitter
  4. radio receiver
  5. Arduino microcontroller
  6. USB cable
  7. computer (web browser)

Materials

  • laser-cut base plate for Arduino
  • mounting screws and rubber feet for base plate
  • radio receiver (315 MHz)
  • egg drop unit:
    • small microcontroller (digispark)
    • 3-axis digital accelerometer
    • small radio transmitter (315 MHz)
    • 9 volt battery and battery holder
    • power switch
    • laser-cut plate
    • padded plastic enclosure

Assembly

  1. Attach your Arduino and the radio receiver to the base plate.
  2. Place the rubber feet on the bottom of the base plate:
  3. Place the Grove shield onto the Arduino. Be careful with lining up the pins.
  4. Connect the receiver to pin D2 (digital pin 2) on you Arduino:
  5. Place the 9V battery in the egg drop batter holder.

Software Preparation

  1. Plug your Arduino into your computer with a USB cable.
  2. Send the Egg Drop Receiver sketch to your Arduino using the Arduino Programmer.
  3. Open the Egg Drop lesson
  4. Set the egg drop module on a flat surface.
  5. Turn on the wireless egg drop module. After about 5 seconds you should see an LED flash on the black circuit board. If the LED does not flash, your battery may be too low.
  6. The first 100 readings from the egg drop module are used to calibrate the module. Any time you'd like to recalibrate the module, make sure the section in the Egg Drop Lesson is running by clicking Start on the control block. Then, press the Calibrate button (while the egg drop module is sitting still on a flat surface).
  7. Move the egg drop module; you should see acceleration values in the data lab and in the individual blocks for each axis above the data lab.

Recording Data

By default, the egg drop lesson will continuously record and keep the last 30 seconds of data in the data lab. To change this, click More Actions and then Recording Options. The Recording Options dialog can configure the length of time to record, how many samples per second to record, and whether to stop recording after the specified time or record continuously. There are steps below for each method of recording.

Recording For a Specified Length of Time

  1. Click More Actions followed by Recording Options.
  2. Set History Length to the length of time you'd like to record for.
  3. Set Recording Mode to stop after history length.
  4. Set Sample Interval to the sample interval you'd like.
  5. Click Ok. The data lab will start recording automatically and stop after the history length that you specified.
  6. Drop the module. All three axes will be recorded simultaneously.
  7. You can now explore the data that was recorded during the fall. Select different axes to view their plots.

If you'd like to start recording again without saving your data, click Start or Reset on the controls. The data lab will begin recording for the specified interval again. To save your data and start a new run, follow the steps in "Saving Your Data" below.

Recording Continuously

  1. Click More Actions followed by Recording Options.
  2. Set History Length to the length of time you'd like to record for. The data lab will keep historical data for this length of time. After this length of time the oldest data will be erased as new data is added.
  3. Set Recording Mode to continuous.
  4. Set Sample Interval to the sample interval you'd like.
  5. Click Ok. The data lab will start recording automatically.
  6. Drop the module. All three axes will be recorded simultaneously.
  7. When the module has reached the ground, click Stop on the controls. You can now explore the data that was recorded during the fall. Select different axes to view their plots.

If you'd like to start recording again without saving your data, click Reset on the controls. To save your data and start a new run, follow the steps in "Saving Your Data" below.

Saving Your Data

  1. If you'd like to keep the run of data you've collected, click the Save/Share option in the More Actions menu to save the data. Fill in a name and, optionally, a description for your data set. If you'd like others to be able to view your data, select Add Everyone.
  2. Click Save when you're done. Selecting the Save/Share option subsequent times will append any new data to the saved data set.
  3. Click the New Data Set option in the More Actions menu to create a new data set. This will preserve the settings you configured in Recording Options, so you do not need to set them again if you'd like to keep the same settings.
  4. Click Start to begin recording data for the next run.

Viewing Your Data

You data will be saved in the Data Hub. From here you can view your data, download a comma-separated version of it, edit it or delete it.

If you have any trouble, email support@manylabs.org.

Technical Details

If you're making your own board, connect the RF data line (yellow wire) to pin P5 on the digispark. Connect the accelerometer SCL (yellow wire) to pin P2 and SDA (white wire) to pin P0. Both the transmitter and accelerometer need to be connected to ground and 5V. Be sure to connect the battery to VIN, not 5V.

Using Two Arduinos

You can use two Arduinos instead of another small microcontroller. The receiving Arduino will be configured the same as above. The transmitting Arduino will need a power source and a different sketch.

Power

The transmitting Arduino will need to be battery powered. You can use a single 9 volt battery or several smaller cells. We don't recommend using Lithium Polymer batteries - these can be quite dangerous when damaged. Your battery holder will need a barrel connector for the Arduino. We sell a battery holder for 6 AA cells that will power the Arduino Uno here.

Sketch

Attach the transmitter to digital pin 5 on the transmitting Arduino. Then, send the Egg Drop Transmitter sketch to your Arduino using the Arduino Programmer. If you need to, you can change the pin the transmitter is attached to in the Code tab of the Arduino Programmer.

Safe Packaging

While the Arduino can take quite a beating, you shouldn't drop it off a rooftop unprotected. We attached our components to a small laser-cut plate so they wouldn't bump into each other, and then wrapped the whole package in foam to absorb shock. Instead, you could use double-sided foam tape to attach the Arduino, batteries, and sensors to the inside of a small disposable plastic container, and wrap the outside with bubble wrap.

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