Connecting External Sensors

Expand the range of what you can test by adding external sensors to Science Journal.

10–20 minutes to prepare the base

Tools and Materials


  • Battery and battery connector
  • Science Journal compatible microcontroller
  • Microcontroller base
  • Screwdriver set and screws
  • USB micro cable

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Science Journal helps you experiment on the world around you with the sensors in your phone. It can also use a wide variety of external wireless sensors to measure things like temperature, pH levels, and force so you can explore even more. Science Journal is compatible with sensors from many different companies.

You can also make your own sensor with a Science Journal compatible Bluetooth LE enabled microcontroller. Microcontrollers are small programmable computers that can connect to a range of inexpensive sensors. By loading different firmware onto the microcontroller you can use it and play with it in different ways. You’ll use the microcontroller to help interpret the information from the connected sensors in the form of graphs and illustrations in Science Journal.

If you bought a compatible sensor, connect it to your phone with the instructions that came with it and then go to step 5.

Prepare the Microcontroller for external sensors

Set up the components needed to record different kinds of data.

1. Load the Science Journal program on your microcontroller.

If you have a Science Journal kit, the microcontroller is preprogrammed with the right firmware so you can skip to the next step.

If you have one of these compatible microcontrollers, click here for step-by-step instructions for loading the Science Journal Sensor firmware onto it.

2. Setup the microcontroller base.

Now that your microcontroller is programmed, use the two screws provided to attach it to the base. This will make it easier to move it around as you do your experiment.

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3. Turn on the microcontroller.

Connect the phone charger to the micro USB port and plug it in. Or, for more flexibility, get power using the 9V battery and connector. You’ll know the microcontroller is on when you see the green light turn on. Unplug the microcontroller when it’s not in use. (RedBear Blend board users: please make sure to set the voltage switch, located right next to the micro USB port, to 3.3V. Changes to this setting will only take effect after a power reset.)

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4. Connect the sensor you wish to use for your experiment.

Depending on the activity you are trying, you may be building your own circuit or installing a prebuilt sensor. You can find information on the sensors used on individual Activity pages. If you are experimenting on your own, continue reading to connect to Science Journal.

5. Connect the sensor to the Science Journal app.

Now you’re ready to test your setup with Science Journal. Get out your phone and open the Science Journal app.

"To pair your microcontroller to Science Journal by pressing the Add Sensor icon in the top right:"

Bluetooth allows you to connect to an external sensor.

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The microcontroller has a unique identifying ID, SCIXXXX, that will show up under available devices; click on this ID to pair with the device.


The microcontroller can only be paired with one phone at a time.

If using multiple microcontrollers, it can be helpful to write the unique identifying ID, SCIXXXX, on a piece of masking tape or sticker and apply it to both the microcontroller base and the phone.

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This will help easily identify the microcontroller when pairing with the phone.

You have now paired your microcontroller to Science Journal and are ready to receive sensor data. Go back to Observe mode and select the new sensor icon in the Sensor menu.

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What’s Going On?

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Bluetooth is a wireless technology standard that uses radio waves to exchange data over short distances from fixed and mobile devices. The Bluetooth tool lets you explore and experiment with external sensors.

Check out the Activities section to explore different external sensors that can be used with the Science Journal app.