What do I need for a good power electronics circuit and PCB design?

Discussion in 'Power Electronics' started by Morad Tamer, Jun 5, 2018.

  1. Morad Tamer

    Thread Starter Member

    Oct 21, 2016
    34
    0
    Hello everyone
    I want to design a High Power Relay Board which I intend to use to turn on and off air conditioners, heaters and other devices that can draw more than 2500 Watts
    I want to be able to control up to 7500 Watts, 30 Amps at 250 Volts AC (Yeah that's really a lot but I like to have extra headroom)
    I know of Optical Isolation and Spark Gaps so I have a bit of background on the topic but really not a lot about when to use them and where to put the components
    I have never made a PCB before
    The thing that made me come here (I hope this is the correct Sub-Forum to post in) is that Dave's videos from EEVBlog are sooooooo long and boring

    Thanks in advance
     
  2. Pedant Engineer

    Member

    May 27, 2018
    129
    39
    Is this for equipment permanently installed then? I ask because you won't get 30A out of a single phase GPO and if you are using 3 phase you have a bigger job than you may have thought.

    Optical isolation and spark gaps; how would they be relevant?

    If the control side is a low voltage environment and not generally electrically isolated from the user or conductors that the user may be able to touch then the area you need to know about is safety isolation barriers, not spark gaps. But first, please indicate; single or multiphase power and nature of control side, ie low voltage? user accessible? connected to other circuits that are user accessible? I need to know the answers before I can go much further with speculating your application.
     
    Morad Tamer likes this.
  3. Hymie

    Member

    Mar 30, 2018
    462
    95
    Someone has already designed and manufactured it for you:-

    https://www.ebay.co.uk/itm/4-Channe...137541?hash=item239e446405:g:YtMAAOSwskJalRW~
     
    Morad Tamer likes this.
  4. Morad Tamer

    Thread Starter Member

    Oct 21, 2016
    34
    0
    Well my idea is that this board will be put at the junction box and have the wiring done through it along with an Arduino for the control signals to a MOSFET which will control the voltage level of the Relay (haven't decided yet on 12 vs. 24 Volt Relays)
    I am not working with 3 Phase power here and there should be no physical user interactions after the initial setup
     
  5. Morad Tamer

    Thread Starter Member

    Oct 21, 2016
    34
    0
  6. Pedant Engineer

    Member

    May 27, 2018
    129
    39
    Morad Tamer likes this.
  7. Pedant Engineer

    Member

    May 27, 2018
    129
    39
    If the entire thing is insulated such that there are no user accessible conductive parts then the low voltage circuits do not need isolation from the mains at all. But beware, you still have to develop this thing and so on, so isolation might be a good idea anyway.
    Just to be clear, if you have, for example, a temperature probe and the circuit it connects to is not isolated properly from the mains (and that typically means a clear barrier of 6.4mm or more) then the entire low voltage circuit must be assumed to be at mains potential and will still require a 6.4mm clear barrier between it and anything the user could possibly touch. so the lead to your probe would need to be double insulated as would the probe itself etc etc. My advice, for what it is worth, use relays with the barrier inherent (easiest way to get the isolation) and maintain the physical separation between mains parts and conductors (relatively easy to do) and you are safe and can sleep easy at night. Sorry if this is teaching grandma to suck eggs.
     
    Morad Tamer likes this.
Loading...