Hardware setup
Building the system
LASER SAFETY
Zapit is an optostimulation device that uses Class 3B laser. A Class 3B laser has sufficient power to instantly blind. The system should be assembled only by qualified individuals. You assume all the risk in setting up the System: the designers of the system are not liable for injury or damage.
In normal use, Zapit produces a 10 cm open beam as this is the working distance of the objective lens. This open beam is unavoidable. When set to a 2 mW time-averaged power stimulating 1 or 2 points per trial the system is delivering 4 mW of power, which is roughly at the threshold for what is safe should you be transiently hit in the eye. When set to >2 mW time averaged power or when using more than points per trial the system will yield unsafe power levels. To use Zapit safely, you should conduct alignment operations at 1 mW or less and use the system in a light-tight enclosure.
Building the system
We have a parts list and CAD files for a custom enclosure available on our Zapit CAD repository. Detailed construction instructions are pending. Zapit can also be constructed from the off-the-shelf ThorLabs parts, although we do not have an example design available at present. We are keen to help others build the system, so if you feel you lack information please make contact via GitHub and we will get you up and running.
Obis Setup
Starting the Obis for the first time
Connect up the Obis as described in its manual. Install the Coherent Connection Software. Connect the Obis to your PC via USB. Confirm that yuo can start the laser and change the output power using the slider in the "Operating Power" tab. You can confirm the reported output power in mW matches the actual power with a power meter.
Enabling analog mode
In the "Remote" tab set the input impedence to 2000 Ohms
Go to the "Advanced" tab. Stop the laser if it is running. Set operating mode to "Analog:Power" and start laser again.
Enable Auto-Start
Remove the sticker on the Coherent Obis box and enable auto-start. This way the laser will turn on when you switch it on. Otherwise you have to connect it to the PC via USB and turn it on that way each time.
The Obis laser responds linearly to the control signal but it does have a non-zero minimum laser power. You should check you setup so you know how it behaves. Likely will find that that the laser can not produce power values below about 0.25 to 0.5 mW. In practice this should make no difference: the only time you may notice it is when examining the rampdown following a low-power photostimulation. The last pair of pulses may not play out as they could be below threshold.
Masking light
It is probably a good idea to add an LED masking light, unless you can otherwise control for the presence of the photostimulation light. Analog output 4 on the DAQ will always produce a 0/5V (TTL) waveform that can be used to gate an LED driver.
Scanner Setup
If your scanners did not come with a PSU, you will need to set up two unipolar DC PSUs to form a bipolar PSU (see parts list). Supply A will provides +V and supply B provides -V. In addition, -V on supply A is connected to +V on supply B and this is ground for the scanner controller. If you have never set up something like this, either get advice from someone who has or do some reading first to make certain you wire up everything correctly.
If you are using ScannerMax galvos and want to swap the short control cable for a longer one, please see this video. You will need to contact the manufacturer to be given the magic command for accessing the advanced settings for the scanner control card.
Wiring the NI DAQ
The DAQ should be wired as follows:
AO0 to the X galvo controller analog input.
AO1 to the Y galvo controller analog input.
AO2 to the laser control analog input.
AO3 to the optional masking light TTL in. Building and setup of this light source is left to the user.
Connect PFI0 to your trigger source.
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