Optical Lickometer questions

kleaman

Hello!

My lab is thinking of using the optical lickometer created by Sanworks, but we hope to interface with our NIDAQ board. What is the output of the lickometer assembly? Does it use TTL pulses / analog signals, or something else? And how would we go about interfacing with our NI board, rather than a Bpod?

Josh

Hello Kleaman,

The lickometer has an infrared emitter positioned opposite to a phototransistor. The infrared emitter needs power. You'd need to supply a 5V DC source in series with a 500 ohm resistor. The phototransistor is normally high resistance, but becomes very low resistance when exposed to infrared light. You'd need to pull an NI digital input channel weakly high by attaching a 15k resistor between the input channel and the 5V supply, and connect the phototransistor between the same input channel and digital ground.

Here's the operating principle: when nothing is in the beam path, the infrared light hits the phototransistor which becomes a low resistance path to ground, pulling the NI input line low (0V). When a tongue breaks the beam, the phototransistor goes back to high resistance, and the 15k pull-up resistor pulls the line high (5V).

I hope this helps,

-Josh

kleaman

Hello,

Your previous response was helpful, but we are still having a bit of trouble with the circuit. Do you have a circuit diagram available?

Thank you,
Kyoko

Josh

Hello Kyoko,

I don't have a circuit diagram for the NI interface, but I can list the connections, referencing the photo on the product page:

All purple wires --> NIDAQ GND
Left-most red wire (as viewed in photo) --> NIDAQ P0.0
Central red wire --> 50 ohm resistor --> NI P0.1
Right-most red wire --> 500 ohm resistor --> NIDAQ 5V

Setup:
-Configure P0.0 as a digital input to read licks
-Configure P0.1 as a digital output to drive the white LED (if it can supply enough current)
-Add a 15k pull-up resistor between 5V and P0.0

I hope this helps,
Josh