Sixteen-Way Data Receiver (A3042)

© 2022 Kevan Hashemi, Open Source Instruments Inc.

Contents

Description
Versions
Design
Set-Up
Operation
Power Consumption
Modifications
Development

Description

[08-MAR-22] The Sixteen-Way Data Receiver (SDR) is a combined motion sensor and telemetry receiver for our subcutaneous transmitters (SCTs). The SDR comes with sixteen Loop Antennas (A3015C) to connect to its sixteen independent antenna inputs. Each antenna input decode telemetry messages and measure their power. The power measurements allow the SDR to estimate the location of a transmitter, on the grounds that the antenna it is nearest two is most likely to be the antenna that receives the most power. These same power measurements allow us to measure the activity of animals, just as we do with our Animal Location Tracker (A3038). The SDR connects directly to Power over Ethernet (PoE), from which it obtains power and through which it performs all communication.

The SDR replaces the Octal Data Receiver (A3027, ODR). The SDR provides sixteen antenna inputs, the ODR provided eight. The SDR provides signal power measurements, the ODR did not. Unlike the ODR, the SDR does not require a LWDAQ Driver (A2071E), making it easier to set up. If we combine the SDR with synchronous video, such as recorded by our animal cage cameras (AACs), the SDR allows us to identify animals seen in the video by correlating their movements with the movements of their implanted transmitters.

We make the SDR by taking an Animal Location Tracker (A3038C), putting it in a box, connecting the detector modules to BNC sockets on the back wall of the box, connecting a Telemetry Display Board (A3042DB) to its flex socket, and fastening the display board behind a window on the front of the box. We connect the ALT's RJ-45 socket to an RJ-45 feedthrough on the back wall of the box. The SDR comes with sixteen A3015C antennas and an Ethernet jumper cable so we can connect it to a PoE switch.

Versions

The following versions of the Sixteen-Way Receiver (A3042) exist.

Version Dimensions Comment
A3042A 55 cm × 33 cm × 12 cm Prototype Sixteen-Way receiver
Table: Versions of the Sixteen-Way Receiver (A3042).

The following sub-assembly versions exist.

Version Comments
A3042DB-A Display board with 200 LEDs and several switches.
Table: Sub-Assembly Versions of the Sixteen-Way Receiver (A3042).

Design

Set-Up

Operation

Power Consumption

Modifications

Development

[07-MAR-22] Nathan reports as follows. "The system is a simple setup of two plastic cages taped together with an antenna on opposite sides. The antennas are spaced 70cm apart. I turn off all the detector modules except for the two that are taped to the sides of the cages. I turn on a transmitter inside the faraday canopy and move the transmitter around the center of each cage, changing position and orientation. I notice that when the transmitter is moving in the center of the cage (about 3 times closer to one antenna than the other) the tracker in the Neuroplayer displays the transmitter being on the correct antenna approximately 95% of the time. That is to say that in this two-antenna system, if an animal was moving in the center of a cage there is a 95% chance that our system would detect that mouse being in the correct cage."


Figure: Animal Location Tracking with Loop Antennas. We have two A3015C antennas on either side of two animal cages. Antennas are connect to detector modules on an A3038C ALT.

[21-MAR-22] We are comparing the Sixteen-Way Data Receiver to the Octal Data Receiver. Nathan writes, "I'm still working on what went wrong with the coaxial combiner, but I was able to get some reception readings that are consistent with past ones so I went ahead and compared the two receptions. I began by only connecting one antenna and comparing reception on different types of transmitters. My results are as follows: For the Faraday canopy test transmitter that is taped onto the end of a stick, I got 75% reception using the ODR as well as the SDR while moving the transmitter to various places in the canopy. Using the rat transmitter, I got 85% reception on both receivers. Similarly, I got 85% reception on both receivers using the pup transmitter with a worse antenna and 90% reception on both receivers using the pup transmitter with the better antenna. None of the transmitters gave different amounts of reception on one receiver than the other. To confirm this, I did another experiment where I moved around each of the transmitters individually while the coaxial combiner output was sent to a T-junction that split to both receivers. This way I could see how much reception I am getting from both receivers at the same time. I never encountered a situation in which I was getting reception on one receiver and not on the other."

Here we see that, by splitting the antenna signal and sharing between the two receivers, we can watch the reception lights provided by both receivers to see if they are synchronous. We find they are: reception by the ODR implies and is implied by reception by the SDR, even though the ODR and SDR do not use the same detection method. The ODR uses a hetrodyning receiver with active demodulator. The SDR uses a direct, narrow-band amplifier with split-capacitor crystal radio.