From: dave@davehigton.me.uk   
      
   In message    
             Adrian  wrote:   
      
   > I'm looking for a USB controlled mains switch (230V AC) that I can  connect   
   > to a PI to turn a mains power supply on and off.   
   >   
   > I've done a bit of digging around on the net, and the options seem to  fall   
   > into two categories, either a relay device which means having to  rewire   
   > the device (which I'd rather avoid), priced around 30Euros or one  that   
   > sits in line (between the device and the supply).  The latter  appears to   
   > be in excess of 100Euros, which is considerably more than I  want to pay.   
   >   
   > Any suggestions on where to look ?  I'm not interested in a wireless   
   > solution, as it is likely to be used in places where signals are not   
   > reliable.   
      
   I did a bit of searching around.  AliExpress sell various models of   
   USB mains-rated relay boards.  Various models offer 5V, 12V or 24V   
   operation.  I see from a later posting that your RPi is in an IP55   
   plastic box, so I'm jumping to the conclusion that you're happy with   
   a bit of DIY to turn it from a board into a solution.   
      
   If I were doing it this way, I think I'd go for a 12V powered board   
   and have a separate PSU, rather than burden the RPi's supply further   
   as many people have problems that are traceable to inadequate power   
   supplies.   
      
   It sounds like you may have to build a USB library for the relay   
   boards - I don't know.   
      
   If I were doing the overall job that you're doing, I wouldn't use   
   USB, I'd use a GPIO pin to switch a different relay board on/off.   
   Much easier (and I've done lots of work on USB firmware and drivers).   
      
   David   
      
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