I'm working on a lamp project that I found online. It's a DIY lamp with a whiskey bottle for the base. The project itself just uses a standard 110V plug that goes right in to the wall, but I wanted to modify this just a little to include some LED's and maybe a timer chip or something, and I was wondering what's the correct way (or if it's even safe / possible) to run a smaller dc circuit somehow off of power taken from the 110 AC? How would you go about doing something like that? I imagine I'd need some kind of rectifier?

  • 4
    \$\begingroup\$ A wall wart? They are cheap and small. A surplus phone / laptop charger, an old monitor external power supply for example. Ditch your idea of directly rectifying 110V without the use of a transformer or switching power supply (very dangerous!) \$\endgroup\$ – jippie Mar 19 '15 at 7:03
  • \$\begingroup\$ +1 jippie. It's not a great idea to be one blown diode away from doing the 60 Hz cha-cha. \$\endgroup\$ – Sean Boddy Mar 19 '15 at 9:32
  • \$\begingroup\$ How much power do your LEDs require? How many LEDs? Big ones? Little ones? The answers to these questions will help us guide you in the right direction. \$\endgroup\$ – Dwayne Reid Mar 19 '15 at 11:48
  • \$\begingroup\$ Oh yeah, I guess I should have included that info huh? Apologies. Well I've got 6 regular green 5mm LEDs. \$\endgroup\$ – Digital Brent Mar 19 '15 at 18:23

There are two ways to handle this. The first is to directly transform your AC 110V waveform down to something much lower, say, 20V. Then, you use a full-wave rectifier to smooth out the 15-20 VAC waveform, and then regulate that down to your 5V to drive your LEDs.

The other way is to full-wave rectify the 110V AC into the ~160V DC. You can then use a switching regulator to bring that high voltage down to what you need it to be, in this case, 5V. Switching regulators should be fairly easy to find on sites like Digikey, and aren't too hard to use.

I think you can also buy an assembled SMPS and use that and directly get your 5V out from the mains supply.

Edit: This only applies if you know what you're doing! If you don't want to expose yourself to potentially lethal electricity, follow jippie's advice and get a wall wart. Unless you're interested in actually designing your own rectifier, most of this information isn't necessary since wall warts are super cheap.

  • \$\begingroup\$ If I use a wall wart though, can I still get enough power to run the lamp or will this thing have two power cords? \$\endgroup\$ – Digital Brent Mar 19 '15 at 18:29

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.