Actions
Forum Thread Details
  • State Suggested Answer
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 311 subscribers
  • Views 416 views
  • Users 0 members are here
Related
See a helpful answer?

Be sure to click 'more' and select 'suggest as answer'!

If you're the thread creator, be sure to click 'more' then 'Verify as Answer'!

Where to begin?

Former Member

I am a hobbyist working on a home automation design.  I am using this project to learn more about electronics and electricity.  Most importantly, I like my house and I'm not keen on burning it down any time soon.

 

The project I'm designing is a small PCB that I'd like to be able to place at every power socket that has an ethernet jack providing data/power to a uC that can control two 120VAC 15A relays.  I'm hoping to expand it with sensors to track power consumption, provide a 5 and/or 10v USB charger port, etc.. etc..

 

My question is, where is a good place (book preferrably) to learn about the correct way to design higher voltage traces and other PCB best practices.

 

Things I'm curious about are:

 

1) The correct/safe way to mix electronic circuitry and high voltage on the same PCB (minimum distances, trace size, layer guidelines, etc..)

2) Code requirements for a device that is to be placed in a wall

3) Learn more about relays, hall effect (for monitoring circuit?)

 

Thanks!

Parents
  • 0

    Hello Ben,

     

    This may sound  a bit patronising but at your state of electronic development the correct way to mix mains and signal voltages on the same pcb is NOT to do it at all.

     

    Use two pcbs - if you google for tear downs on usb battery chargers you'll see that many of the reputable ones made by big name manufacturers still stick with this principle.

     

    There are rules for mains separation but working on your own is not the best place to be when you start out.

     

    I always try to avoid having mains on a board with low level signals because it makes them difficult to debug safely.

     

    The easiest and safest (but not cheapest) way to measure mains current is to use a current sensor (search Farnell for them)  of the type where the mains carrying wire thread through. Current transfomers (search F again) are much cheaper, 2291968 is cheap and safe, the Wurth ones are not so good as you need to break into the mains wire.

     

    If you put the little Murata transfomer on your low level board you can measure mains current safely.

    You could trust your relays to give you isolation but I would prefer to use ones in sockets with screw terminals arranged with the coil on one side and the contacts on the other.

     

    To learn more just Google for things like "pcb design for mains voltages"

     

    Here's a link to get you started http://www.smps.us/pcbtracespacing.html

     

    but please find more sources and follow up the references.

     

    MK

  • 0 in reply to michaelkellett

    Thank you for the suggestions.  Don't worry about sounding patronising... I'm posting here for a reason and I have no illusions as to my current ability!

     

    Fortunately this is just an educational exercise.  I like to learn topics by picking a problem that I can directly identify with and go from there.

     

    My thought was to design a solution where I could control a socket using a relay and monitor the activity at the socket level.  The relay I was looking at is the Sharp S216S02 which appeared to offer pretty effective isolation.  I have also been reviewing the ACS712 series current sensors but I like the complete isolation (in exchange for bulkiness) that the Murata provides.

     

    The ability to debug a board safely (or just handle it in general) is a critical point in favor of multiple PCBs.

     

    Thanks for the quick response!

Reply
  • 0 in reply to michaelkellett

    Thank you for the suggestions.  Don't worry about sounding patronising... I'm posting here for a reason and I have no illusions as to my current ability!

     

    Fortunately this is just an educational exercise.  I like to learn topics by picking a problem that I can directly identify with and go from there.

     

    My thought was to design a solution where I could control a socket using a relay and monitor the activity at the socket level.  The relay I was looking at is the Sharp S216S02 which appeared to offer pretty effective isolation.  I have also been reviewing the ACS712 series current sensors but I like the complete isolation (in exchange for bulkiness) that the Murata provides.

     

    The ability to debug a board safely (or just handle it in general) is a critical point in favor of multiple PCBs.

     

    Thanks for the quick response!

Children
No Data