20-40V 2-10A DC Power Supply

[Krumlink]

I thought it was just a toroid, without a Transformer.

 

[Nigel Goodwin]

I thought it was just a toroid, without a Transformer.

Would you be happier if we used it's full name? "toroidal transformer", commonly called just a "toroid".

 

[Krumlink]

Well I thought you could make a power supply with JUST A TOROID, as in the little squiggly thing in the pic. I know how to make the PS shown, but how with JUST the "squiggly thing".

 

[Krumlink]

I looked at jameco and I found a 28V 2A Transformer, and I will use that with a bridge rectifier on the output. I will also put some smoothing capacitors on it. Is there anything else I should put on it?

 

[dknguyen]

I looked at jameco and I found a 28V 2A Transformer, and I will use that with a bridge rectifier on the output. I will also put some smoothing capacitors on it. Is there anything else I should put on it?

Wires to connect the things

EDIT: And a fuse on the transformer input.

 

[Hero999]

A transofmer with two 15V secondaries it probably your best option. A switch can be used to connect them in series and parrallel: for the higher voltage setting connect them in series to get a peak voltage of 42V and connect them in parallel for a peak voltage of 21V. For better voltage controll, just add a variac to the primary side.

 

[Krumlink]

Good news is, is that I built a PS with a 12V Transformer (had a actual output of 16V) and put a rectifier on it to make it 14VDC. Then with a bulk capacitor in parallel it lifted that up to 20.1 VDC I am guessing that because of the 60hZ 14VDC the capacitor would store the charge up then release it at a low state, increasing the Voltage? (the movie verifies the 20VDC)

 

[Leftyretro]

Good news is, is that I built a PS with a 12V Transformer (had a actual output of 16V) and put a rectifier on it to make it 14VDC. Then with a bulk capacitor in parallel it lifted that up to 20.1 VDC I am guessing that because of the 60hZ 14VDC the capacitor would store the charge up then release it at a low state, increasing the Voltage? (the movie verifies the 20VDC)

Well what is really going on there is that the filter caps will charge up to the PEAK AC voltage, which is RMS voltage X 1.4, minus diode voltage drops.

The load can cause this peak cap charge voltage to drop depending on the amount of current draw and the size of the caps, generating a AC ripple voltage riding on the DC level, that can be seen with a scope on the main caps.

Also the rectifier can only replenish the caps at 100/120hz rate. The caps are supplying load current 100% of the time while the transformer/rectifier can only supply current when it's instaneous voltage rises above the existing filter cap voltage. Think of the caps as being replenished in brief 'sips of the straw' at 100/120 Hz from the transformer/rectifer.

Lefty

 

[Hero999]

[latex]16 \times sqrt{2} - 1.4= 21.22[/latex]

 

[Krumlink]

Hero, your maths is almost right

I am measuring 20.1VDC

 

[Hero999]

On load?

That wouldn't surprise me.

 

[Krumlink]

Yup, across a 100ohm 50W resistor I am getting 20.1VDC.

 

[Hero999]

Exactly, the voltage will drop when you put a load across it, my calculations were for when there's no load.

 

[Krumlink]

Oh I see