Wiring 5v to a 12v powersupply

[LayZ]

I have something with these specs

Voltage:5V
current：0.8A

And I want to wire it into :
12v 5A PSU


Would it be fine to just put it directly into the positive and negative termials of the 12v psu without problems? Whats the restrictions here if any when wiring to psus?

I don't know much about wiring yet and am about to do quite a bit of research in the next month or so.

 

[Bluejets]

Use a 5v 1A plug pack or similar.

Connecting to the 12v unit will result in smoke and ash.

 

[LayZ]

Is there something that can be used to wire it to the psu? Some kind of resistor I guess?

I'm wanting it to be switched onto the psu not plugged into the wall or even switched into the wall which could be acceptable but not ideal.

 

[(*steve*)]

Can you explain what you're trying to achieve?

Connecting two different power supplies of different voltages together in parallel is... odd.

Or are you wanting to connect a 5V device to a 12V power supply? If that's the case, the "something that can be used to wire it to the psu" is called a 5V regulator. You can wire up a regulator, or take the easier route of using a 5V supply.

Changing 12V to 5V at 0.8A using a simple regulator will generate quite a bit of heat because you are wasting a lot of the energy. Depending on what you are doing, a simple switch mode regulator module (like this one available from ebay for a couple of dollars or less) can do this far more efficiently. There is also the advantage that you don't have to do much more than wire it up. Oh, you will have to adjust it for 5V BEFORE you connect up the load.

 

[LayZ]

The post wasnt clear, I'm wanting to take a usb powered device with
Voltage:5V
current：0.8A

and power it with
12v 5A PSU

and have it on an on/off switch powered by the psu.

After re-reading your post, I don't mind paying another 2 dollars or so to get some kind of resistance/conversion for the efficiency. Whats the suggestion in that case?

 

[Audioguru]

A resistor is not a voltage regulator.
You were told to use a 5V regulator that will probably cost more than a 5V 0.8A PSU.
The 5V from USB is regulated, but many PSU's are not regulated and might blow up your USB powered device.

 

[LayZ]

A resistor is not a voltage regulator.
You were told to use a 5V regulator that will probably cost more than a 5V 0.8A PSU.
The 5V from USB is regulated, but many PSU's are not regulated and might blow up your USB powered device.

Your post is just confusing.

The regulator provides something like a resistance/conversion thats all I was saying.

Now you make it seem like even using a regulator wouldnt be a good option and possibly be hazardous.

The regulators can be gotten for less than a dollar after searching, the wall plug would probably be near that or a little more like double, price in this amounts is not a problem the functionality I want is. you added extra confusion.

 

[(*steve*)]

Whats the suggestion in that case?

See the link I gave.

 

[LayZ]

Can 2x of the
Voltage:5V
current：0.8A

Be wired together onto the regulator without a problem or only one per regulator?

 

[dave9]

.. switch mode regulator module (like this one available from ebay

On that listing it states "Note: We do not offer this item to the state of Illinois, US. , we don't offer, don't sell and don't ship to the state of Illinois,US."

Never seen anything like this before and I'm not in IL but it makes me wonder, does IL have some kind of applicable restrictions or is this seller in trouble with IL somehow??

 

[(*steve*)]

Can 2x of the
Voltage:5V
current：0.8A

Be wired together onto the regulator without a problem or only one per regulator?

maybe, but for the cost, I'd get one for each.

 

[(*steve*)]

On that listing it states "Note: We do not offer this item to the state of Illinois, US. , we don't offer, don't sell and don't ship to the state of Illinois,US."

Never seen anything like this before and I'm not in IL but it makes me wonder, does IL have some kind of applicable restrictions or is this seller in trouble with IL somehow??

Maybe they don't like Mike Pence?

Oops, Illinois not Indiana.

 

[dave9]

Can 2x of the
Voltage:5V
current：0.8A

Be wired together onto the regulator without a problem or only one per regulator?

Yes you could put two in parallel, but as you increase current doing so, note the temperature rise of the regulator board. It is within the specs of the module but those specs may not be very conservative for the design as-implemented on that tiny circuit board with limited heatsinking.

In other words they're rating based on the max current an LM2596 can handle but that max depends on better heatsinking.

 

[LayZ]

Regulator would be fanned by 40x40mm fan where its being placed... Parallels not too important right now after thinking about it.

The chips were rated 3a and the devices .8a if that changes anything having the numbers.

I have heatsinks but didnt plan on using them here I could throw one on them if needed... should 0.8a x1 be fine on heat? I did read something earlier about heat and current I think it was in one of the listings.I dont mind buying two though if that were a better option for parallel.

Heres the chinese listing for cheapest price, these would almost for surely be cheaper than the wall plug version as well last wall plugs I bought for all kinds of dc motors (from china also) were all $1.50+. They will also almost for surely ship to you as well.

 

[davenn]

Heres the chinese listing for cheapest price, these would almost for surely be cheaper than the wall plug version as well last wall plugs

that covers the conversion problem which is the same type of unit Steve linked to earlier in the thread

so do you already have a 12VDC source ?

 

[LayZ]

Yea I have the psu I want to use a 12v 5a power supply.

I have bigger ones that are like 12v 30a but if this works fine I will be able to always use a 5a instead saving ten to twenty dollars per unit.

 

[KJ6EAD]

Is there any reason why you can't just use one of these car USB chargers or the circuit board within? Get one with two 1A outputs or better if you like.

 

[LayZ]

The circuit board on those can be wired to the 12v PSU? Sounds like a good solution for dualling.

If it has a 1a output (supplying more) is it like wiring and gauges? IE People often overwire as a common practice instead of using mininal 26 gauge they may use a 24 gauge in that application.

I have a couple laying around to test with.

 

[Audioguru]

Some cheap Chinese ebay circuits are not certified to be safe (banned in Illinois?). My Electrical Utility Company gave away free compact fluorescent light bulbs so that people could try them and use less electricity than old incandescent light bulbs. But the new bulbs dripped burning plastic!

They were recalled and replaced. The company explained that the Chinese manufacturer stole the certification certificate from an honest competitor so these bulbs were never tested and certified to be safe.

The LM2596 is a switching regulator that produces fairly high switching noise and at low currents it goes into a discontinuous mode where it switches on and off. Do you want the 5V to have ripple and switch on and off?
A linear regulator dont doo dat.

 

[LayZ]

Not sure what you mean by ripple, I want it hooked up to a 16mm switch that then when pressed latches and turns on the device that is wired into the 12v psu via lm2596.

I get quite a few pcbs from china. Actually I buy a ton of stuff from china. If they arent good I can test using the car adapters pcbs.. from china. I don't have a problem testing items if they come at the right price. China is very competitive and I rarely run into issues considering I buy a ton of items from there, atleast 60 items in the last month and it will only increase.