No More Wall Warts: The DC-DC Buck Step-Down Converter

A few months ago I saw this little gem on eBay and snagged it for something like $3.50. After a month (gotta love Chinese envelopes) it showed up at my door.

dcdc2

My mom asked, appropriately, “What the hell is that?”

To her, probably nothing. To me, however, a very cool gadget.

If you’ve experimented with electronics, you’re probably aware of the really annoying fact that all these devices require different voltages and currents and practically no two are alike. If you’re exceedingly lucky, your device will take a standard 12V 1A center positive wall-wart, available in droves. Or maybe a 5V 1A supply (those are also common).

But a lot of the time, you end up with equipment that requires odd voltages. That’s where this device comes in handy. Plugged into the input, I have a 19V laptop transformer that I got for $6 on Amazon Prime for a friend (I thought I lost her adapter, I later found it, ended up with it). Clipping off the annoying connector revealed two beautiful red and white wires which I stripped and tinned. Many of these adapters have coaxial arrangements of the cables (this one has one of those little plastic cylindrical enclosures. Maybe that’s where it changes from coaxial to double strand?).

Basically this converter consists of a simple switching circuit with a built in inductor. Two filter capacitors on the input and output stabilize the voltage. By switching very quickly between charging and discharging the inductor it’s able to maintain a steady voltage across the outputs which is stepped down from it’s input. The max voltage it can produce is 2V less than the input or something like 26V, whichever comes first. It can supply something like 2.5A.

Basically, for $10 I have a 2.5A fully adjustable power supply. A tiny screw allows fluid adjustment along a very wide range. When combined with a 19V supply at 3A, it’s capable of supplying most every gadget I have in my collection with the necessary voltage. Is it stable as the dickens?

No.

It tends to jump a little high after I dramatically reduce the current draw (releasing the PTT of a radio). But all in all, not bad for $10. And you can always attach a gigantic capacitor across the outputs for stability (check out the MIT Flea Market if you’re interested in gigantic cheap capacitors for arc welding or other uses. be careful though they’ll burn you into a fried chicken if you’re not careful).

Here it’s powering my Turnigy Accucell 6 universal battery charger to give my radio batteries a boost. I have a 25 Amp supply but for charging at 1A current, that’s a little wasteful (not to mention huge).

Bottom line is that I would highly recommend perusing eBay for one of these things. The screw sets the output voltage which doesn’t change as input voltage varies, and these are supposedly 95%+ efficient.

The Andre seal of approval is bestowed upon this Chinese gizmo.

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