Setting up 3-channel recordings

[gabbieportlock]

I am currently attempting to set up a 3-channel photometry system so that we can record from a red, green and isosbestic channel in a single brain region. I have attached a photograph of the current set up (washers to keep the pyPhoto board in place incoming!). Please could you advise on: 1) whether my current minicube will support the 3-channel setup and 2) how I can adapt the setup to incorporate the 3rd LED (405nm) which is currently not plugged in. I believe that I need to get an external LED driver (could you recommend a cost-effective product?) and then plug that into the 405nm CLED I have, then into the digital 1 port of the PyPhotometry board. If you could let me know whether I’m on the right lines that would be very helpful 😊

[ThomasAkam]

Hi @gabbieportlock,

This minicube looks suitable for doing 3 color red/green/isosbestic recordings using the pyPhotometry 3EX_2EM_pulsed mode. For this configuration you would make the following connections to the minicube:

• Blue (~470mn) LED, controlled by acqusition board LED_1 output, connected to minicube E1 port
• Green (~560nm) LED, controlled by acqusition board LED_2 output, connected to minicube E2 port
• UV (~405nm) LED, controlled by external LED driver triggered from acquisition board Digital 2, connected to minicube IE port.
• Minicube photoreciever output F1, connected to acqusition board Analog 1.
• Minicube photoreciever output F2, connected to acqusition board Analog 2.

Regarding external LED drivers, I think a suitable option would be the Thorlabs LEDD1B. It has a BNC input which can be configured as a trigger, and you can control the LED on current over a wide range using manual controls on the unit.

[julesbartlett]

We have a further question about connections to and from the minicube as we are currently using all available ports. There aren't actually any ports at the F1 and F2 locations (see pics attached). Is there a way to get around this issue and still use the suggested modification of adding the LED driver?

[ThomasAkam]

Hi @gabbieportlock,

Apologies for the delay getting back to you. My understanding from the pictures you sent is that the photoreciever outputs F1 and F2 on the minicube are the BNC connectors which you have connected to the pyPhotometry board analog inputs, which is correct for the 3EX_2EM mode. You also have 3 fiber optic input ports on the minicube for LEDs, which are labeled E1, E2 and IE, which are resepctively for the 470nm, 560nm and 405nm LEDs. So in total you have 2 photoreciever outputs and 3 LED inputs which is exactly what you need for the 3EX_2EM acquisition mode.

[julesbartlett]

Hi Tom,

Thanks for all your help so far. We have connected up the additional led and driver as shown in the picture below.
I have also included screenshots from the GUI during a recording. We just wanted to check that the signal we are getting looks correct. The control channel especially appears to be clipping on on the 0 line and we weren't sure if this is expected or a power issue.

Any advice or reassurance would be much appreciated.

https://photos.google.com/photo/AF1QipNvhWXlgYEclt9LVfTZBi5bOkg96sN_c6FZZSCh

[ThomasAkam]

Hi @gabbieportlock, this does not look correct to me. You ideally want to get all signals to around 2.5V at baseline to ensure you have good signal to noise levels. Are you confident that the LED being used for the 3rd channel is outputing light?