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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

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.

 

 

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.

 

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...

 

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

 

View from the other side.

 

Behind the power switch, LEDs and fuse holders.

 

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.

 

There is order to the madness... :-)

 

 

 

So does it work?

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

 

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.

 

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.

 

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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