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dhhagan / py-opc

Python wrapper for the Alphasense OPC-N2 built around py-spidev
MIT License
30 stars 26 forks source link

why i can`t supply the OPC-N2 with the raspberry ? #83

Closed metallicano closed 5 years ago

dhhagan commented 5 years ago

Hi @metallicano Can you be more specific so I can help? Thanks!

metallicano commented 5 years ago

in the documentation of the py-opc`s is it : The OPC requires at least 250 mA, so powering directly through the RPi is not an option....why?

dhhagan commented 5 years ago

Ahh okay. The new RPi's can only output 100 mA from all GPIO pins combined, whereas the older models can only output 50 mA total (16mA per pin max).

You can try it from the 5V pin, but according to the specs, it shouldn't work..

patricktokeeffe commented 5 years ago

@dhhagan I think you may have misread the specs page. I/O pins are limited to 50mA but the 5V pin is tied directly to the power rail. It can source whatever the power supply can provide, certainly over 1A. See also:

Standard procedure in our university research lab is to power the OPC from 5V & G pins to avoid potential grounding offset issues that cause SPI comms to choke. I've had units running for multiple years in this configuration.

dhhagan commented 5 years ago

@patricktokeeffe ahh okay - good to know! I'll change the docs then when I have time unless someone wants to send a PR with the changes..

patricktokeeffe commented 5 years ago

@dhhagan I'd be happy to submit a PR later tonight

metallicano commented 5 years ago

THANKS :)

metallicano commented 5 years ago

SO, i can connect the opc to 5V raspberry pin and it will work ok ?

patricktokeeffe commented 5 years ago

Hi @metallicano you tried it out? if so how is it working?

metallicano commented 5 years ago

Yes, it works

metallicano commented 5 years ago

yes it is working by the moment "good", i will to compare it whith other sensor, the DUSTTRAK 8533 and then i'll tell you the results.

El lun., 13 may. 2019 a las 9:25, David H Hagan (notifications@github.com) escribió:

Closed #83 https://github.com/dhhagan/py-opc/issues/83.

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