Hi,
I am using the S and GND terminals on the interface board to detect licks (along the line described in https://hhmi.flintbox.com/technologies/e6b6e309-fb3d-47bf-8dff-cd7a5d9fc205). In detail, we connect a S terminal with a water lickport, and GND terminal with a plastic tube covered with a copper sheet where a mouse would enter and sit inside during an experiment (the latter connection is through a banana cable; a male banana cable is connected to the GND terminal, and a female banana cable jack is connected to the copper sheet). So, the idea is that when a mouse licks the lickport while sitting inside the tube, the lickport will be short-circuited, and there will be a current from S to GND leading to a lick detection. I confirmed that the lick detection works very well when I directly touch the lickport with the male banana cable connected to the GND terminal, or with the copper sheet covering the tube (of course now the male banana cable is connected to the tube). But, it doesn't work when the mouse licks the lickport, or when I touch the lickport with one hand and the copper sheet with the other hand. Based on these observations, I believe the issue may have to do with the threshold for lick detection, i.e. the threshold current required for the lick detection is too high, so the lick detection doesn't work when the resistance between S and GND is high enough. Is there a way to solve this problem?
Many thanks,
Byungwoo
p.s. A couple days ago, we tried to connect an additional circuit to the interface board to resolve the issue, but this still had problems b/c of the weakly pulled up 5V at S terminal. We removed a resistor on the interface board that we believe is responsible for the weak pull up, but the weak pull up persisted. We believe that the weak pull up is maintained internally by an arduino inside the state machine. Is there a way to remove this weak pull up without messing up other things? We are thinking of changing the firmware to remove it, and it would be great if you could comment whether it's safe to do so, or what's the best way to do it.
