5v PSU

[zachtheterrible]

For my project I am going to need 5 5v, around 500ma-1A power supplies. they need to have little or no ripple, because they will be used with 433mhz tx's and rx's, and even a small ripple will mess things up in a large way.

I was looking at wallwart supplies but don't know if this is the best way to go. Does anybody know of a very simple and cheap circuit that will work well? Or a place to buy them cheap?

thanx :lol:

 

[zevon8]

You may find a cell phone charger or router or hub wallwart is just the thing. Very small, switching supplies. Often you can get these on Ebay, or at surplus places, or you may know someone who has a phone they don't use anymore. The one for my old phone was about the size of a "C" size battery and could do 5 volts at 1 amp, hardly got warm and had a very clean output.

 

[zachtheterrible]

Yeah, id love to get some switching power supplies, but im sure they're expensive. ill check on ebay though. in fact ive got a 5v 1A switching supply for my phone :lol:

EDIT: Actually they're quite inexpensive. I found a 5v 2A switching supply for $4 a piece, buy it now. Thanks for the advice :lol:

 

[audioguru]

I bought some name-brand one year old, new 5V/2A tiny switching power supplies at an electronic parts surplus store near me for a little more than $2.00CAN. That's less than $2.00US. They weigh and cost about the same as the power cord!
They work very well. :lol:

 

[zevon8]

If you go EBay'in look for a Nokia ACP-12U, it s the adapter for several phones, and it gives 5.7 VDC @ 800 mA.

They are listed from about $3 and up. It is about the size of 2 Bic lighters side by side.

 

[zachtheterrible]

even better, thanx :lol:

 

[Nigel Goodwin]

even better, thanx :lol:

You can also buy regulated wallwarts, these are far better quality, and any recent ones are usually switchmode anyway!.

 

[zachtheterrible]

ohhh, so thats why a couple PSUs I was looking at were "regulated"

 

[Optikon]

Yeah, id love to get some switching power supplies, but im sure they're expensive. ill check on ebay though. in fact ive got a 5v 1A switching supply for my phone :lol:

EDIT: Actually they're quite inexpensive. I found a 5v 2A switching supply for $4 a piece, buy it now. Thanks for the advice :lol:

Caution:

You said originally that even a small (you didnt quantify) amount of ripple will cause problems in your circuit. Well, if that's true, buying a nice small efficient switcher is the worst thing you can do. It will generate much higher frequency noise than linear types with ripple (unregulated). If you go with the switcher, expect to see that switching frequency throughout your circuit. Whether or not the amount will bother you, you'll just have to see.

 

[adamthole]

I would reccomend using like a 12V wall wart or somethind around their and then a 7805, although I'm not sure how much amperage the 7805 can do.

The wall warts, unless you are talking about a different kind I do not know about, are very noisy devices and will actually put out around 6 or 7V if they are rated at 5V, depending on the amperage used.

 

[zachtheterrible]

Yeah, I guess that I will just have to buy one and experiment with it. I really would like to use a switcher but im not sure now. Would the regulated like Nigel mentioned be any better suited?

Yeah, I definetly am not going to go w/ a regular wallwart.

 

[CoTang]

I would reccomend using like a 12V wall wart or somethind around their and then a 7805, although I'm not sure how much amperage the 7805 can do.

The wall warts, unless you are talking about a different kind I do not know about, are very noisy devices and will actually put out around 6 or 7V if they are rated at 5V, depending on the amperage used.

Do those wall warts output over 5 amps? And yes, some 7805 will output 500ma- 1A depending on what you get, and you have to be able to supply that amount from the wall wart too.

 

[Optikon]

I would reccomend using like a 12V wall wart or somethind around their and then a 7805, although I'm not sure how much amperage the 7805 can do.

The wall warts, unless you are talking about a different kind I do not know about, are very noisy devices and will actually put out around 6 or 7V if they are rated at 5V, depending on the amperage used.

7805 can do 1 amp with an appropriately sized heat sink. Get the TO-220 package and put it on a heat sink. Rough 7805 scenario. Lets say need 5 to deliver 5V at 1amp each. 12V input. Each one will burn 7W to deliver 5W (thats the main problem with linears) each one is 41% efficient. So, your 12V input must be capable of delivering 60W (5x 12W) That's a BIG wall wart! I doubt you can find one, and if you do, you'll spend a months worth of allowance to get it.

Now, a 60W swithmode can be had in a 2"x4" geometry and get better than 85% efficiency. But remember, if you need each supply to deliver 1A at V, you will be burning up 7W in the 7805 for each supply. This power dissipation is too much for those small TO-220 "U" shaped heat sinks. You need a larger one possibly costing around $3 - $5

If you can live with the switching noise, it would be much better to make all the supplies (main 12 and 5x 5V) switchmode.

There are ways to make "low noise" switchmode, but it involves more complicated techniques and certainly more money.

 

[zachtheterrible]

I'll buy one of those switchmodes and see how well it suits my needs.