Increasing power supply's Amperage

[amando96]

Hi, i'm using this printer power supply, as my breadboard supply, it has a 5v rail, that i can only draw 0.3 amps from, and a 24v rail that i can draw 1 amp from it, what should i substitute so i can pull more amps?
I don't have a schematic, i can get a photo though.

 

[MikeMl]

Look for a surplus (or left over) Wall Wart that puts out 5V at 1 to 3A. I have a closet full of those things. I buy them at garage sales for $0.50 (US)

 

[Sceadwian]

You should substitute a new power supply...
You can't just alter the circuit to get more current out of it, not practically at least, it's rated at it's given current for a reason.
ATX supplies are a good choice for bench supplies, they can supply hordes of current at 3.3 5V and 12V as well as small amounts of -5 and -12V but not 24V. If you need the 24V supply with higher amperage try looking for more printer supplies, you're not going to find too many that are more than 1-2 amps at 24 volts though. You can find 24V supplies that will supply much more current online though. How much at which voltages do you actually need?

 

[mvs sarma]

perhaps not the 12V section, unless you load the 5V, as the control loop is on 5V. With no load on 5V, 12 V can barely give .25amps, perhaps.

Amando96 could tell the make and model number of the printer power supply

may be by re-design of control loop by shifting to 5V line, he could achieve the needed 1 amp load from a printer supply.

 

[Sceadwian]

Loading the 5V section is trivial, and generates negligible extra heat. I can pull 35 amps off the 5V line of the supply I have and 16amps off the 12 volt line. It cost me nothing because it was from an old PC.

 

[mvs sarma]

Loading the 5V section is trivial, and generates negligible extra heat. I can pull 35 amps off the 5V line of the supply I have and 16amps off the 12 volt line. It cost me nothing because it was from an old PC.

of course, after loading 5V section, you can always take load from 12V also.
but the op, as I understand wants only 5V load, from a printer power supply , supposed to have 24V and 5V both, if i am correct!!!

 

[Sceadwian]

It's a moot point till amando specifies exactly what currents he needs at the two voltages he's listed. He can always use the printer supply he's currently using for the 24V 1Amp, and use a separate 5V supply for the 5V side. No amperage requirements were ever listed.

 

[mvs sarma]

OK I get you. Thanks, Sceadwian !!

 

[amando96]

I'd be safe with 5v at 1.5-2 amps, the 24v rail is going to have an LM317 so i can have adjustable voltage, so max of 1.5 amps with 24v(max of the 317 i can get)

I really only need more than 300mA at 5v... the 24v rail is fine.

I have a few old computers, some i use, but the power supply seems like a good idea.

 

[mvs sarma]

better to have switch mode DC to DC converter than LM317.
Even at 0.5amps, linear model gets too hot and heavy heat sink would be needed

 

[jbelectric777]

I use a 120V line multi tap secondary 45VA transformer. It gives me 3.0 to 30.0VAC fed through a full wave rectifier and then fused to protect what Im working on,any electric supplier has the transformer and the rest are just diodes sized for the maximum load. RS for fuses or even an auto parts store. Jim

 

[zaidi_ayan@yahoo.com]

hi im using a home made power supply of 5v,3.3v, and 12v suply with the current of 1 amp...but now i want increase current...from 2amp some one tell mewht should i do??????

 

[MikeMl]

A bigger transformer, heavier rectifiers, bigger filter capacitors, bigger pass transistors for the regulators, larger heat-sinks, larger box to put it all in. In short; it sounds like a new power supply to me...

 

[mneary]

hi im using a home made power supply of 5v,3.3v, and 12v suply with the current of 1 amp...but now i want increase current...from 2amp some one tell mewht should i do??????

If you can remove it from the old supply without damaging it, in some cases you can re-use the main power cord. But that's about it.

In most cases it's worth while to leave the old unit as it is in a working state.

 

[Sceadwian]

5V 3.3 and 12? That's tailor made for an ATX supply =) They're easy to work with and will supply well more than 2 amps for current, as those are the voltages that PCs need the most of, although I think the most modern PCs lean towards using the 12 volt rail and regulating it at the source nowdays rather than relying on a lot of 5 and 3.3V current.

 

[UnloadedQ]

Check out National Semiconductors line of "Simple Switchers". These even come as kits with all values set up for you. A DC-DC switcher will let you trade off current for voltage so your 24W DC output (12V at 2A or 24V at 1A) turns into 5V at 4.9A. The LM2600 / LM2700 series has chips that range up to 6A and require little heatsinking. Linear Technology has similar chips, like the LT1270, that go to 10A. All are simple, all have app notes, all can be had from Digikey or Mouser at fairly low cost. But, none of these will compete with a proper supply with the needed outputs you can also get from both DigiKey Corp. | Electronic Components Distributor | United States Home Page and Mouser Electronics - Electronic Component Distributor