Poke detection jitter?

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Poke detection jitter?
#1
Dear Josh,

first of all: thanks a lot for your help so far. We now have a complete visual stimulation / 3d tracking system with BPod at its core that I am rather happy with.

One thing, though:

It seems as if the poke detection is rather jittery sometimes (not always...). We have a .7 state machine with custom-printed ports. Everything (incl. electric parts) is by-the-book. The problem is that sometimes port in & out events are triggered in rapid succession when the mouse enters a port. Finger-poking the ports then leads to jittery detection as well. All of our 8 ports are similarly affected. I bound ttl events to the port state changes and the changes seem to jitter around 10-100ms. In our script this triggers early withdrawal events en masse which is problematic. This seems to come and go, though, which makes me believe that this is an electrical issue. Also: the problem does not seem to be consistent - with pokes being detected just fine on some occasions.

I know that this is tricky to troubleshoot - but are there obvious steps I could follow to see what the problem is?

Cheers,T
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#2
Hi T,

One thing you may want to look at is sources of infrared light in your assay (including sunlight). The phototransistors in the ports have a visible light filter, but they are transparent to infrared - so if a rodent or finger hovers near the port, reflected IR near the detection threshold may be the culprit. I'd try to keep the ports shielded from the IR lamp as much as possible, or play with the position and intensity of the IR source.

-Josh
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#3
This is an excellent point. We indeed flood our arena with IR for tracking. I will check if that's the culprit - but it seems likely. 

Thanks,T
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