This may be more suited towards the Elec engineering SE, but thought I'd ask here as I'm working with the Pi.

I recently picked up this relay board, and soldered it all together using their guide, however it seems not to be working, that is when I run i2cdetect y - 1 it doesn't show anything in the 0x20 cell, which I think means the relay isn't connecting to the pi?

How do I go about debugging what the problem could be? I presume I'll have to start testing individual components to see if any of them have blown? Can that be done on the board itself, or will I have to un-solder the components?

If it impacts at all, when I first connected the pi to the relay via the ribbon cable, I accidentally connected it upside down (the red-strip was not at the top of the pi, where the 5v pin is)

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    You give almost no details of what you have done, so it is hard to help. I gather it is using i2c Have you enabled this? i2c-bcm2708 is blacklisted in /etc/modprobe.d/raspi-blacklist.conf – Milliways May 20 '14 at 7:10
  • @Milliways apologies, I've updated the description with a link to the guide I followed, but yes, I did comment out the bcm module from the black list. – Psytronic May 20 '14 at 13:44
  • Looking at the schematic, putting the connector upside down should be no problem (besides not working of course). Does i2cdetect y - 1 show anything? Did you check the dip-swithes? Could you post a picture of the assembled board? Maybe some component is placed wrong. You can certainly test the board manually. I could give you some pointers if you need (do you have a multimeter?). – Gerben May 20 '14 at 20:03
  • The guide says i2cdetect -y 1, not i2cdetect y -1. Are you sure you typed that in correctly? – krs013 May 28 '14 at 4:17

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