[02-APR-20] The Implantable Intertial Sensor (A3035) is a wireless accelerometer and gyroscope that may be implanted beneath the skin of a small mammal or attached to the exterior of a fish. As we describe in our IIS Technical Proposal, the design of the IIS is motivated by an experiment to measure the movement of freely-swimming fish in a water tank. The IIS is equipped with a 13-mm helical antenna and two 5-mm helical leads we use to recharge the battery. Antenna and leads are insulated with silicone. The circuit itself is encapsulated in epoxy and silicone. To attach the device to a fish, we wrap it in a custom-made rubber sleave, which we can super-glue to the fish's scales or skin. We recharge the A3035's battery with a Batter Charger (A3033E).
The table below lists the existing versions of the Implantable Inertial Sensor (IIS).
|A3035A||ML920 11 mA-hr||0.9||1.0||8||Acceleration xyz 16-bit 128 SPS
Gyroscope xyz 16-bit 128 SPS
The A3035B provides 128 sixteen-bit samples of each of x, y, and z components of acceleration, and x, y, and z components of rotation. The total number of samples per second is 6 × 128 = 768 SPS. Total quiescent current we expect to be around 1.2 mA, so we anticipate operating life of 8 hours for one charge of the 11 mA-hr battery.
The IIS is managed by a field-programmable gate array (FPGA) in a 2.5-mm square package, LCMX02-1200ZE. This device provides both volatile and non-volatile memory as well as thousands of programmable logic gates. It is capable of implementing arbitrarily-complex stimuli in response to a single command.S3035A_1: IIS Version A Schematic.
[04-JUN-20] The A3035A is powered by an ML920 manganese-lithium rechargeable battery. This battery may be recharged through the A3035A's two recharge leads, which protrude a short distance from the device, within the loop of the antenna.
We recharge the ML920 through two internal silicon diodes using an A3033B battery charger. Charging to 80% capacity will be complete in twelve hours, but 100% capacity requires a forty-eight hour charge.
The A3035AV1 appears to need no modifications, but does require a booster power supply to start up.
[03-APR-20] We receive 25,000 custom-made rubber bands that fit around our smaller-sized implantable devices, as shown below.
This rubber adheres well to super-glue. We can glue two bands together instantly with super-glue gel. With the rubber sleave around the device, we can glue it to the exterior of a fish, and pull it off later. We throw away the rubber sleave, recharge the battery, and use another sleave for the next experiment.
[20-AUG-20] We have 100 of A303501A in 10 panels of 10.
[13-OCT-20] We have 3 of A3035AV1 first article. Inactive current consumption 1.1 μA. Turn on and we are able to scan the logic chip.
[14-OCT-20] We prepare A3035A No1 with our initital P3035A01 firmware, which does not communicate with the accelerometer or gyroscope, but instead transmits zeros at 512 SPS. We get good reception, current consumption 173 μA. We load ML920 battery, but the battery cannot supply the start-up current reequired by the LCMXO2-1200 logic chip. We try ML1220, but it can't do it either, nor a BR1225, alghouth a BR2477 is able to get the board started, as well as a 10-mAhr LiPo battery. We can jump-start the board by attaching an external 2.6-V power supply at power up, and after that the board runs fine off its ML920.
We are able to read the BMA423 accelerometer chip identifier register (0x00) and the BMG250 gyroscope sensor time register. We see the values we read from the sensors in the SCT signal plotted in the Recorder Instrument. We conclude that all connections in the circuit work, and approve second article. We leave the A3035A with 11-mAhr battery transmitting.
[15-OCT-20-] After fourteen hours, the A3035A is still running.