Using Multiple EmotiBits in the same space

Q: 

I'm interested in using EmotiBit to capture data from groups of people, say 10-30 per session. But I'm worried about wifi supporting that many devices in the same space and how many devices I'd need to run the oscilloscope software. Does the device need a constant wifi connection to collect data or can it record to the SD card without wifi?

A:

You can definitely run multiple EmotiBits on the same network. We have actually tried this before in a classroom setting at UNR.

You rightly pointed out that WiFi support becomes important at high device counts, so I would recommend setting up a local hotspot or just use an additional router to create the network (as we did). You can also manage the traffic by being clever with the EmotiBit unicast settings. Check this FAQ for more details.

We have also made some improvements to the EmotiBit architecture after our classroom experiment, for example, now, Each EmotiBit is displayed on the EmotiBit Oscilloscope with the device ID, so it is easy to identify which EmotiBit the Oscilloscope is connected to.

If you need to continuously stream data from every EmotiBit to an EmotiBit Oscilloscope, you will need 1 oscilloscope per EmotiBit. On Windows, you can just start multiple instances of the application and connect to a different EmotiBit on each instance. But if all you want to do is record data locally on the SD-Card, you can just use 1 Oscilloscope and sequentially connect to each EmotiBit and start the record session.

One thing to note is that EmotiBit uses periodic time syncs with the EmotiBit Oscilloscope to increase timestamp accuracy. So I would recommend making sure the EmotiBit is connected to the EmotiBit Oscilloscope at the beginning and end of the recording session.

The sequence would be something like:

1. Connect to an EmotiBit.
2. Start a recording session
3. Keep it connected to that EmotiBit for ~20 secs
4. Connect to the next EmotiBit
5. Repeat the steps.
6. ...
7. ...
8. ..
9. Towards the end, connect to EmotiBit.
10. Stay connected to 20 secs
11. End recording session.
12. Repeat for all EmotiBits

Hope this helps!