Egg Shield - NO2 readings OPEN CIRCUIT

[VinceC]

Hi all,

Just got my shield today. I always seem to get "Open Circuit" readings on my NO2 sensor?

The sensor seems properly seated in the socket, as I can measure 1.9V across pins 1-3 and ~4k ohm across pins 2-4.

Any ideas?

Thanks,
Vincent

[Victor Aprea]

Hey Vincent,

Hrm... a report of open Circuit implies that the the ATtiny88 is reading 0V at the ADC input (which is pin 23 for NO2). Most of the time when I've seen this it's because the sensor is actually not fully seated, and it actually takes a fair amount of force to get them seated in the sockets, but it seems you've already checked that. I'm not sure how you are numbering the sensor pins, but the pin labelled "S-" with respect to GND is the voltage in question. The only other likely reason I can think of for getting an Open Circuit reading a hard short between that pin and GND. You can check for that with the continuity setting of your DMM with the circuit powered off. 

I guess another possibility (less likely IMHO) is that your sensor is defective and actually is presenting itself as an open circuit. You can check for that by substituting a fixed value resistor (or a jumper wire even) in place of the sensor (across the S+ / S- socket pins) and seeing if the output still reports Open Circuit.

 

If that's the case, you've got a manufacturing defect, I'm afraid, and you can send it back to us for a repair/replace at no charge. 

On a side note (and not to hijack our thread), I wonder if the group is the best place for this type of correspondence. I would offer that it would be better to use our support forum at forum.wickeddevice.com (redirects to osqa.wickeddevice.com). It's based on the same engine as stackoverflow.com and just seems like a better way to handle support-related questions in a sustainable and organized way. 

Kind Regards,

Vic

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Victor Aprea // Wicked Device

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