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Best Way To Mount High Voltage Circuit

Discussion in 'General Electronics Discussion' started by Skyman, Jul 10, 2015.

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  1. Skyman

    Skyman

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    Feb 17, 2015
    Here's my situation. I'm working with a circuit that involves mosfets that will be used as switches to control a 48V supply. I need a way to mount the circuit (solder it onto a board or something similar) but I've heard that veroboard will not hold up against the high voltage/current. My question: What is the best way to "mount" a circuit with a large voltage like 48V and a current of around 2A?
     
  2. Gryd3

    Gryd3

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    Jun 25, 2014
    For high voltage, you need isolation... Tracks, traces, and wires physically further apart, or separated with insulation between.
    For high current, you need better/larger conductors... Resistance in small/poor conductors causes a voltage drop which leads to heat build-up and potentially the wire or trace burning up.

    Try looking at this page for some ideas... I can't vouch for it being 100%, but you can see how the different numbers will alter your design.
     
  3. BobK

    BobK

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    1,688
    Jan 5, 2010
    48V and 2A are not high voltage or current. Normal construction techniques are fine.

    Bob
     
    Harald Kapp and davenn like this.
  4. davenn

    davenn Moderator

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    Sep 5, 2009
    I agree with Bob on that one
     
  5. Gryd3

    Gryd3

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    Jun 25, 2014
    Sorry.. forgot the link I wanted him to look at.
    http://www.desmith.net/NMdS/Electronics/TraceWidth.html
    The outcome should be well within the specifications of the board he wished to use.
     
    Harald Kapp likes this.
  6. Skyman

    Skyman

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    Feb 17, 2015
  7. Gryd3

    Gryd3

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    Jun 25, 2014
    Your call... You will have to use jumper wire on the underside of the board to connect everything... or you can look into 'wire wrapping', which I think is actually a very cool skill to have...

    Anyway, I should mention that something like this : http://www.digikey.com/product-detail/en/8015/V2009-ND/415998
    May be suitable depending on the layout of your board.
    The hole spacing is roughly 2.5mm, with 0.5mm clear between each pad. Now, this is below the calculated value you noted, but there are a couple tricks you can use.
    First, the calculator you used will give you excessive values to be on the safe side, so you have a little wiggle room.
    Secondly... if the gap between the pads is 0.5mm, and you need more, simply leave a row or two of unused pads between the +48V wires/traces and the Ground wires/traces.
    Remember that as soon as you lower the voltage, you no longer need the spacing.

    Additionally, if you are concerned with the thickness of the copper pads, you can simply double the width to compensate. So instead of using one row for the 'high' amperage current path, use two. They can be two separate paths, but it would be best to put the paths side by side and actually tie them together.

    Now... The voltage you are using and the current you are using isn't technically called 'high', you will find that you will need to carefully plan your circuit. Linear regulators will get very very hot, and the higher current path(s) can always be reinforced by laying a small piece of wire along the path and soldering to that instead of relying on just the solder to join the little pads together.

    So.. while I gave you a calculator to see what happens with the numbers, I would also discourage the need to go to a bunch of special steps to order special board requiring unique construction methods.

    Let us know what you think, and if you are willing to share the schematic, we can help out more.
     
  8. Skyman

    Skyman

    22
    1
    Feb 17, 2015
    I can't figure out how you came up with 0.5mm clearance, could you show me where or explain how you derived this? Anyway, judging by all of your responses it seems safe to use a normal soldering prototyping board.

    I should also clarify about my circuit. I will be making a pinball machine that has two separate voltages, 5V for LEDs/Logic Voltage and 48V for solenoid coils like the flippers. Any component running on 48V will only be powered in very short intervals (250 milliseconds the longest). If two or more coils (flippers/bumpers) fire at the same time, that is when the current would reach 2A or so. This shouldn't happen very often and even when this does occur it will only be for a very short time (like 250 milliseconds). Sorry for not sharing this earlier.

    Basically, the controller (Arduino) will send a 5V signal to the gate of a n-channel mosfet when a certain button/target is hit (let's say that the player presses the flipper button on the side of the cabinet). The drain of the mosfet is connected to the 48V power supply and the flipper coil. The source is connected to ground. When the mosfet turns on, 48V is supplied to the flipper coil, thus hitting the flipper bat up. Once the flipper bat is in the upright position, it switches to a much lower power winding coil (the current drops to something like 100mA).

    Other circuits, like the one for the scoring display, will be on a separate prototyping board.

    Hope this helps. If you have any more questions feel free to ask.
     
  9. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    The layout provided on the page you linked me will give you dimensions for the holes, pads, and spacing.
    0.100" Spacing from hole to hole, and the outer Diameter of the pads are 0.080" leaving a gap of 0.02" between. Convert this to metric and you get a clearance of roughly 0.51mm between the outer edge of the pads.
    I think this will work just fine for your application... BUT, you should include bypass diodes on the solenoids to divert any back EMF that may arise... as they are heavy inductive loads. Put them as close to the solenoid as you can.
     
    Last edited: Jul 14, 2015
  10. Skyman

    Skyman

    22
    1
    Feb 17, 2015
    Okay sounds good. All of the solenoids already have fly back diodes soldered to there terminals, so I have that covered.
     
    Gryd3 likes this.
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