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Simple accessories transformer in 3 easy steps
Warning! This design uses a mains power supply, thus treat the whole circuit as being at mains potential. Disconnect before making any adjustments etc. If you need to use an oscilloscope or other grounded instrument for debugging, the circuit MUST be operated through an isolating transformer. The finished design MUST be enclosed in a suitably insulated case, and if pushbuttons are used for switching on or off, they must have mains rated insulation.
This information is provided 'as is'. Readers should only attempt to build this design if they are competent at electronics assembly and understand the dangers of mains voltages. No responsibility is accepted for any damage, injury or death (however serious) or disruption of the space-time continuum caused by anything remotely connected to this website.
Things you'll need:
Plastic case
Transformer
Fuse holder
Screw terminal connectors
Wire
Fuse (Rated at 1 or 2 amps whatever the transformer can handle or the maximum you will draw)
Mains rated switch (if you want one)
3 or 4 amp bridge rectifier rated higher than the fuse if you want DC instead of AC power
The first thing in building an accessories transformer is to find the appropriate transformer you can buy one new or salvage one from a used electronic device. If you salvage one fist check to see if there's a short between the primary and secondary coils with an ohm meter you shouldn't get a reading. Then Connect the input to the supply and run the transformer for a while with no load to see if it gets warm makes any sound or smells but don't leave the transformer unattended and be careful of the primary winding.
It is recommended that you use a plastic case as then if something goes wrong (hopefully it shouldn't) the case won't go live. If using a metal case make sure it is properly earthed.
Step 1
First drill the holes to mount the transformer on the bottom of the case. Then drill holes to mount the to screw terminal connectors at each end and the hole for the input and the fuse holder.
Step 2
Mount the screw terminals on the ends one on the inside of the case and one on the outside under the one on the outside drill two small holes for some wire to go through. Bolt the transformer to the base of the container and Connect the transformer out to the outside screw terminal by running the wire through the holes you just drilled for them.
Step 3
Run your input line (the one with the plug on the other end) into the case on the other under a hole by the inside screw terminal. And screw to the bottom of the screw terminal. Then run one of the transformer inputs to one of the top terminal holes. Runs the other transformer out to the fuse and then connect the other side of the fuse to the other top terminal on the input side connect the earth to the case of the transformer.
The transformer is done now test the output with a multimeter an make sure the voltage is correct and then wire it up to your layout (in this case my Lionel gateman)
Warning if using a metal case make sure it is properly earthed.
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