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Safety - Make Transformer Safe

Discussion in 'General Electronics Discussion' started by Paul Lockwood, Dec 5, 2014.

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  1. Paul Lockwood

    Paul Lockwood

    Dec 1, 2014
    While going through all my old kit hidden in the loft I came across a 220V to 12V 3.5 Amp AC transformer.
    I would like to have a go at converting the output AC to DC as per one of the YouTube videos I've recently seen.

    However I would ideally like to have the transformer in a safe location when doing this and only having access to the 12v wires. If I end up using this in a permanent project then it would also need to be secured.

    The transformer is one of those that are held inside a plastic mould that has two flaps either side with screw holes to fit it to something. The connections are fairly exposed with the two input and two output right next to each other.

    Is there a project box or something similar that would cater for this?

    A question that may cover all this is how do you secure your components / PCBs in a case so that they don't move around when picked up?

  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    A plastic case (aka project box) would be sensible. You'll have to look for a box that has sufficient space inside for the rest of your electronics.
    A fuse on the primary side to protect from overload or similar failure is mandatory. Make it changeable by using a fuse holder like e.g. this one.
    Sepoarate the secondary circuit (rectifier, capacitors etc. a good distance away from the primary circuit (mains), such that even in case a mains wire comes loose there is no chance of this wire touching anything on the secondary side.
    For additional protection you may want to conenct the secondary ground (-) to the protective earth conductor of the mains cable.

    Screw all components (transformer) and PCBs to the case for fixation. Use distance studs or bolts to hold the PCB at a distance from teh case so you have enough space for the wiring underneath.

    Note that you will deal with dangerous/lethal voltages on the primary side (mains). Take the requisite precautions to avoid any risk of electrical shock. Have someone experienced check your setup before you connect it to mains.
    KrisBlueNZ likes this.
  3. Bluejets


    Oct 5, 2014
    Avoid using metal screws ( or any metal components) that protude through to the outer case.

    Better to use a plastic case as above that has a seperate internal mounting plate.

    Earth all metal components internally and get a qualified electrician to check before you power it up.
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