This guide will take you through the assembly of the entire miniscope system.
Head Mounted Scope Assembly
A brief outline of steps to assemble the scope can get found here: File:AssemblingScope.pdf.
Filter Set Installation
Excitation LED PCB Installation
CMOS Imaging Sensor PCB Installation
Data Acquisition System Assembly
We generally have all surface mount (SMD) components assembled on the DAQ PCB by a third party PCB assembly house leaving only the through-hole components to be assembled in lab. It is possible to have the assembly house place both SMD and through-hole components but it is more expensive and through-hole components are relatively easy to solder. A good through-hole soldering tutorial can be found here.
Through-hole component assembly
If you decide to have the through-hole components assembled by an assembly house you can skip this section. Below is a picture highlighting the necessary through-hole components that need to be soldered in order for the DAQ PCB to function properly.
- Description of components
- SW4: Reset button the resets can reset the USB Host Controller
- U5: EEPROM (memory that holds the DAQ firmware) socket. You can also solder the EEPROM IC directly to the board but I prefer using an IC socket so I can swap out the EEPROM if necessary
- K1,2,3: Each are 2pin 0.1" headers
- J9: A 3pin header used with a 2pin jumper to select power source for the microscope
- J3,4,5: SMA connectors used for GPIO pins
- J6: We currently solder a short coax cable with SMA connector to these pads. This will be updated soon to a replace this with a proper PCB footprint
Once all SMD and through-hole components are in place the switches and jumpers need to be properly set for uploading firmware and powering the microscope.
Below shows the default configuration of the 3 SMD switches on the DAQ PCB.
Below shows the possible K1, K2, and K3 jumper configurations.
The scope power jumper, J9, sets the power source powering the head mounted scope. In most cases the USB power configuration should be used and no DC power supply needs to be hooked up the the DC jack on the PCB.
The cabling between the head mounted scope and DAQ hardware is only a single coaxial cable. A coaxial, or coax, cable consists of an inner conducting wire surrounded by an insulating dielectric and then outer, generally grounded, shield. In our system the inner conductor carries power along with a data link and bidirectional control channel and the outer shield needs to be grounded. Our hardware dynamically adjusts for signal attenuation and small voltage drops across the cable but carry should still be taken to minimize these loses.
Properties to look for in a coax cable are
- 50ohm impedance. This is absolutely necessary.
- Light weight and highly flexible. We like to use coax cables with an outer diameter of 1.5mm or less. It is important to note that as the diameter of the cable decreases, so does the length it can support.
- Handles bandwidths up to 1GHz. For short distances this requirement can be reduced.