Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Newbie looking for ideas and help with power supply project

Redsled

New Member
Hello everyone. I’m new to the forum and relatively inexperienced with small circuitry. I am a tinkerer and know some basics. I want to build a power supply for the following application:

My wife collects powered snow globes. They are all battery powered but have an alternate power option dc port. They range from a couple at 7v down to most which are around 4v. A couple of the snow globes have small motorized parts but mostly the power is for small lights and electronic music so they are all pretty low amperage (the highest is 2.2 amp).

I have a couple power adapters that came with a few of the snow globes but mostly, I spend time loading batteries every year. I’d like a centralized power station. My project is a 110v ac to dc converter, which is simple; however, I want to build a single device with multiple dc power ports. Maybe that isn’t terribly complicated, but I want a few ports to be a set voltage (say 5.4v) and a few other ports to have a different set voltage, and have yet some other ports with adjustable voltage so I can accommodate new snowglobes in the future. In total, I’m hoping to have somewhere around 25 ports but if that is too many, I’d limit it to the maximum safe number of ports and build additional units as needed.

I’ve watched YouTube videos for a single port power adapter and I could certainly handle that kind of build, but I‘ve never found any videos about building even dual ports, let alone the configuration I’m proposing. I’m curious if I’m going to be dealing with major overheating issues and since I’ve never seen such a contraption for sale, I’m wondering if there are other issues I’m not even thinking of that makes this project a non-starter. If anyone has an opinion they’d be willing to share, I’m all ears. If it’s a feasible project, I think it would be a great starter project for me with some guidance from you all.

Thanks in advance, Dave.
 

danadak

Active Member
You could take an adapter and "hang" off it several linear / adjustable regulators.

For the fixed voltages just calculate the two R's needed. Calculation in datasheet.

For adjustable replace one R with a pot -

lm317-voltage-regulator-circuit.jpg



I would fuse each supply, and pay attention, in datasheet, to bypassing requirements.

You also have to determine heat sink requirements -




Regards, Dana.
 
Last edited:

crutschow

Well-Known Member
Most Helpful Member
they are all pretty low amperage (the highest is 2.2 amp).
2.2A is not low amperage for battery powered devices.

As a start you need to measure all the voltages and currents needed.
Do you have a multimeter and know how to do that?

For the lower amperage devices, the LM317 regulator suggested by danadak is a good choice.
They are cheap and nearly bullet-proof.
 

sagor1

Active Member
See the price of LM338K ? Wow. Glad I saved a dozen "pulls" way back when...
I can't see s snow globe using 2.2A either, are you sure about that current? The LM317 is a good regulator, but should have at least a small heatsink on it. Heat from the LM317 will depend on the input/output voltage difference as well as the current draw, so keep that voltage difference small if possible (3 to 5 volts).
 

sagor1

Active Member
A cheaper option may be those buck/boost converters from places like Ebay or Amazon. They have much lower heat dissipation, and each can be adjusted to the voltage you want.
 

danadak

Active Member
If you look at the buck/boost parts make sure you check out their minimum
load requirements to stay in regulation. Some have that as a limitation.

Regards, Dana.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
If you look at the buck/boost parts make sure you check out their minimum
load requirements to stay in regulation. Some have that as a limitation.

All the ones I've used work fine with no load (or at least a 10Mohm multimeter load), you're also unlikely to get such details on cheap Chinese modules anyway.
 

danadak

Active Member
Look at device part number to effect switcher, and then its data sheet. The
architecture and other chip device implementation design decisions
determine if chip / design / magnetics / mode require minimum load.

Also look at datasheets, many spec ratings with min load constraints.

Just google DC to DC minimum load, national semiconductor or TI, lots of hits.

Converters operating in continuous mode need minimum loads to stay out of
discontinuous mode operation. LM2596 and the jillions of variants. many
used in low end modules.



Regards, Dana.
 
Last edited:

atferrari

Well-Known Member
Most Helpful Member
Hola danadak

circuitspedia.com could require some serious proof reading.

1641419223579.png
 

Latest threads

Top