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The ultimate DCC Power Supply

"nec
plus ultra"


by Doug Teggin - January 2006

I
have a normal 16 volt AC transformer for my DCC layout. It does the job
well, but I needed more power. I want to add further boosters, ensure a
clean source of power for my point decoders and install 12V lighting
circuits around the track. Looking around at prices of about £36 for a
42VA (3amp) transformer and about £47.50 for a 70VA (4.6amp) transformer,
I realised that I needed 3 or 4 of these things, the bigger the better.

So I thought: Why not make one? So I did.

I found a plan on Huib Maaskant's site
for a 6 x 16V AC power supply fed by a toroidal transformer with 2 x 16V /
10amp circuits (300VA).

Toroidal transformer

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I modified his plan slightly. Original
plan here: Pwrsply.pdf
(78 kb)
. On my plan (below), I increased the main power fuse to 2.5amps and I
added 1N4001 diodes in series to all of the circuit indicator LEDs to
protect them better from the AC current.

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I
bought the components from Conrad, having to order a few times as you
never get everything in one go. Hopefully this shopping list at the bottom
of this page will prevent you from having to do that if you decide to
build one of these yourself.

So here are the bits and pieces laid out.

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I
first marked and drilled all the holes in the case. This was a bit of a
mission as the box is steel and very hard. I suggest drilling a small
pilot hole of about half the width of the final hole to prevent any issues
with miss-aligned holes. If you need to drill a 12mm hole, get yourself a
12mm bit - don't do what I did and use a 10mm bit and an hour with a
file...

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Here,
the power connectors, power switch, the fuse holders and LEDs are fitted.

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View
from the other side.

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Behind
the power switch, LEDs and fuse holders.

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Everything
wired up. Relatively straight forward. The wire I used was ridged
household wire that gave some structural strength to the diodes and
resistors. Note the toroidal transformer is bolted to the chassis. The box
is earthed to the earth connector on the power plug.

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There
is order to the madness... :)

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So
does it work?

Yes, I am pleased to say that it does. 16
volts across all the outputs. All working fine.

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The
multimeter checks the voltage. All is fine. The 1amp fuse on the mains
power side of the transformer in the original plan by Huib Maaskant did
blow as I expected it would. The 2.5amp fuse that I have added in the plan
above works fine.

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When
a device is plugged in to one of the circuits and the fuse is removed (or
blows), the red LED for the circuit illuminates. It does not illuminate if
there is no device using the circuit and that circuit's fuse is blown.

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I'm
very happy with this project. I was slightly worried that I wouldn't get
it together as I have not built any circuits for a while, but it was quite
easy. It is very solid and safe.

Shopping
list
Cost
I
bought the toroidal transformer on eBay from Antek (Antek's
eBay shop
)
£20.00
The
rest of the components come from Conrad (Conrad
France site
). I have noted that some of the reference codes do not
work on the British Conrad site (www.conrad-direct.co.uk) so you should
perhaps look at the item and find a corresponding one from Conrad UK,
Radio Spares or Maplin Electronics. The Conrad (France) code is highlighted.
1
418250-62 RESISTOR 1% 0.6W 1 KOHM
£00.21
1
418439-62 RESISTOR 1% 0.6W 33 KOHMS (added to the one above to
make 34KOHM
£00.21
12
418277-62 RESISTOR 1% 0.6W 1.5 KOHM
£02.15
1
162248-62 DIODE 1N 4004
£00.07
12
162213-62 DIODE 1N 4001
£00.74
7
550825-62 FUSE HOLDER 6.4X31.8 MM. 6 X
£19.22
1
068959-62 10 FUSE 6,3X32MM 2,5 AMP SLOW
£01.51
1
068961-62 10 FUSE 6,3X32MM 4 AMP SLOW
£01.51
1
521442-62 METAL BOX 300X102X195MM
£15.76
4
523151-62 FEET ABS 21 MM FOR BOX
£01.38
6
064580-62 INSULATED PLUG 4 MM RED
£05.78
6
064581-62 INSULATED PLUG 4 MM BLACK
£05.78
1
064464-62 DOUBLE THROW SWITCH ON/OFF 10A
£02.68
6
730661-62 BANANA PLUG 4MM RED SCREW
£04.33
6
730670-62 BANANA PLUG 4MM BLACK SCREW
£04.33
6
184586-62 LED 5 MM RED CQY40
£01.24
6
184730-62 LED 5 MM GREEN CQY72
£01.44
1
184934-62 LED 5 MM YELLOW CQY74
£00.24
13
178942-62 LED SUPPORTS 5MM PLASTIC
£02.68
1
612600-62 POWER SOCKET 10A/250V
£00.83


Total

£92.09


So I figure that if I bought 4 70VA
(4.6amp) transformers at £47.50 each it would cost £190.00

This 300VA (20amp) power supply cost just
less than half
that. So it's a good deal overall.

 
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