The Insight Extender is a comprehensive accessory which adds several functions to the Emotiv Insight. While maintaining a small package size the system packs a higher capacity battery (1900mAh), a 2500V isolated power supply and 2500V isolated USB connection, a local microprocessor, and Contact Quality display system.
The Insight Extender has to deal with a lot of different use cases.
1. Offline charging mode: Insight Extender is simply plugged into a USB power source and its internal battery is charged. In this mode the local microprocessor has to negotiate with the USB host to provide as much current as possible, then limit its charging current to the agreed amount so as not to damage the host. This requires significant battery management options including programmable charge current limiting.
2. Offline Dual charge mode: Insight Extender is plugged into a USB power source and also into a dormant Emotiv Insight. Extender negotiates with the USB host for maximum current and also manages the charging process for both Insight and the Extender batteries.
3. Online pass-through mode: Insight Extender is plugged into a PC USB port and also into the working Emotiv Insight. In this mode, the Bluetooth connection is disabled and data is sent to the PC directly over the USB link. Direct connection between a device with electrical skin contact and a (possibly) mains powered external device can only be safely accomplished if there is at least 2500V isolation between all pins on the mains powered device and the head-mounted unit. This includes the 5V USB power supply and all of the data pins. The Insight Extender uses a switched-mode power supply through a 2500V-isolating transformer to regenerate a safe 5V power source for the Insight headset, and also a 2500V isolating transformer on each USB pin. In addition to this function, the Insight Extender needs to negotiate the maximum available current from the host in order to charge both the Extender and Insight batteries while in use.
4. Online powered mode: The Insight Extender is plugged into a power pack and the headset is able to operate continuously using the normal Bluetooth 4.0 LE connection to your mobile device or PC. In this mode the system can safely be worn while in use.
5. Mobile mode: Insight Extender is not plugged into any external power source, but the Extender battery powers the Emotiv Insight headset. This mode simply extends the usable life between recharges, Insight operates normally through the Bluetooth 4.0 LE connection to your mobile device or PC.