Pmod PIR

[sinmo]

Hello

I recently got a Pmod PIR board. The specifications indicate the capability to adjust sensitivity for both small and large objects. However, by turning the potentiometer on the board, I noticed that it only affects the duration of the output signal, determining how long it remains active. Could you please clarify the connection between this adjustment and the sensor's sensitivity? or am I missing something? Thanks in advance. 

 

[artvvb]

Hey sinmo, welcome to the forums.

I'm sorry for the delay, but I've reached out internally to the engineers who worked on this product to see if I can get some more information.

Thanks,

Arthur

[sinmo]

Thank you. Looking forward to hearing from you. 

[artvvb]

Got some more information:

The primary intent of the multivibrator circuit is to be able to control the length of output pulses. It was explained to me that this would be useful in scenarios where the output pin was connected to a microcontroller interrupt pin (or a GPIO connected to an interrupt pin), as the longer pulse would prevent multiple events from firing repeated interrupts, thus eating up CPU time. It could also be useful when using an FPGA development board, as it could impose less strict requirements on a project - it could effectively debounce the signal for you.

As for the lines about sensitivity in the feature list, they seem to be unrelated to the multivibrator functionality. It's possible that they were included as, during the design of the product, Digilent was considering several options for the mounted sensor and whether multiple variants of the Pmod would be produced with different sensor variants. If this is the case, it would be an error in the datasheet - I'm still looking into it and we may cut these lines.

You can find more information on the sensor used and its sensitivity in these documents:

https://mediap.industry.panasonic.eu/assets/custom-upload/Components/Sensors/Industrial Sensors/Passive Infrared Motion Sensors/PaPIRs_Nutshell_Flyer_23.pdf

https://mediap.industry.panasonic.eu/assets/custom-upload/Components/Sensors/Industrial Sensors/Passive Infrared Motion Sensors/ds_ekmc160111_v63_en.pdf

Thanks,

Arthur

[sinmo]

Thanks for the clarification. Fyi, here are the features listed for this product:

- High sensitivity center for small movements of small objects

- Normal sensitivity center for larger movements of large objects

 

So based on what you found this product doesn't have such capability? 

[artvvb]

That's correct. Sensitivity is fixed based on the sensor type. It may be possible to depopulate the sensor and replace it with another compatible sensor from the same line, however this would likely void the warranty. I sincerely apologize for the incorrect documentation and am working to make sure that we correct it. In the meantime, I will be reaching out shortly via direct message to provide contact information for our customer service team, in case you're interested in pursuing a return.