04. 1P2C DAQ Guide
If you have any questions please email hfawce@bu.edu
The DAQ Box has four major components to assemble:
- The Lighting Circuit
- The Digital to Analog Converters (DACs)
- The UCLA Data Acquisition Board
- And the USB Hub
This assembly guide will cover the wiring and assembly of each component before covering how the four fit together
The Lighting Circuit
The developed lighting circuit enables multiplexing of the LEDs to allow for simultaneous recording in two distinct spectral bands. By switching between blue and green excitation for each frame, the single interleaved video can be deinterleaved to produce two videos in different channels. It also allows the two LEDs on the miniscope to be controlled manually or through the computer by the accompanying program, Video Capture. Below is the diagram for the lighting circuit PCB which was designed in Eagle PCB. The CAM data is attached as a zip file here
The following images show the PCB design in Eagle PCB (left) and the general circuit (right)
The circuit diagram shown incorporates BuckPucks, LEDs, power adapter, transistors, switches, potentiometers, D Flip Flop, arduino mega, resistors, and capacitors
When the PCB linked above is printed, it should look ike the one shown below:
To assemble this board, the components are listed in the DAQ parts list. A bill of materials for this single board is below for clarity:
For ease of use, female header pins were added to the ports on the board with no listed component. After assembly, the board should look something like this:
Digital to Analog Converters (DACs)
In order to prevent the LEDs from overheating when the intensity is increased, each channel needs to be run through a digital to analog converter or DAC. One DAC is used per channel.
We used two I2C DAC breakouts from Sparkfun
We assembled these with one set of four male headers and two sets of two 90 degree male headers. First, the unbent end of a set of two 90 degree male headers was inserted into the ports OUT and GND facing up on one DAC (the top one) and down on the other (the bottom one). Next, the row of four headers was inserted into both boards (long end into the lower board) into the SCL, SDA, VCC, and GND vias of each board. The assembled set of two boards are shown from the side (left) and from above (right):
The top board corresponds to the green channel (channel 1) and the bottom board corresponds to the red channel (channel 2).
UCLA DAQ The next component is the UCLA Data Acquisition board (UCLA DAQ). This board comes fully assembled and ready for use. The USB connector should be plugged from the connector on this board to the USB Hub. If, after successful initial use, the board appears to be malfunctioning, try replacing the L13 100μH inductor marked with a red star on the diagram below.
USB Hub The final component added to the DAQ Box is a USB hub to condense the number of outputs of the system. We use an Anker 4-Port USB 3.0 hub. Connect the USB from the UCLA DAQ and the USB from the Arduino into two open ports, then plug it into a USB 3.0 Panel-Mount Type A Male to Type A Female Cable. This hub was purchased from Amazon
DAQ Box For ease of use post-assembly, the full data acquisition pipeline is contained in a single DAQ box. We 3D printed a custom box that fits all of the components. If you would like to use the same box, the .stl file for this part is attached here.
All of the required components are placed within the box and then wired up according to the diagram below.
Place the Arduino Mega on the pegs built into the box. Next, the UCLA DAQ should be placed such that the three connectors protrude from the holes highlighted in green in the figure below. Then, the lighting circuit should be placed in the box with the DB26 connector lined up to the corresponding cutout in the side of the box which is highlighted in blue in the picture below. The Panel-mounted extension cable should align with its cutout (highlighted in red) and screwed into place. At this point, the USB hub can be plugged into the female end of the panel-mounted cable and the USB cords from the arduino and the UCLA DAQ can be plugged into the hub.
Within the box, several connections still need to be made. First, the connected DACs are plugged into ports 18 through 21 such that the two pairs of exposed male headers sit in the gap between ports 21 and 22. Next, the output pin on the bottom DAC is connected with a male to female cable to the DAC2 port on the lighting circuit board. In the same way, the output pin from the top DAC is connected to the DAC 1 port on the lighting circuit, the GND on the bottom DAC is connected to DAC 2 GND, and the GND on the top DAC is connected to DAC 1 GND. This wiring is shown in the figure below.
At this point, the internal wiring in the DAQ Box is complete and the power, DB26, and coaxial connectors can be plugged into their respective ports on the side of the box. The full wiring diagram with all parts including the active commutator can be seen below. For more information on the construction of the active commutator, please see the commutator wiki page.