Power supply

Hi I am building a prusa i3 and uncertain about power supplys, at the moment im waiting on motors and arduino to arrive but i want to be able to test the equipment once it arrives.
I salvaged this from a pc but uncertain it will work can anyone point me in the correct direction please thanks

sorry for the big picture

17 A on the 12 V line should be sufficient unless your heated bed takes a lot more than 10 A.

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havn't got the heat bed yet thats nxt months purchase

to be honest i am going to use this power supply just to check the equipment like the ramps and the motors, once the motors and the arduino arrive

Yea, 17A is plenty for the motors/etc.

But if you want a hotbed, I'd recommend finding a supply that's higher than 250W total. Maybe 350+

I would recommend a 12v 30a led power supply, at this point no one should be messing around with an atx psu, they provide unreliable current and voltage, and are a pain to set up. someone needs to change the instructions on the wiki page.

aduy Wrote:
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> I would recommend a 12v 30a led power supply, at
> this point no one should be messing around with an
> atx psu, they provide unreliable current and
> voltage, and are a pain to set up. someone needs
> to change the instructions on the wiki page.

How do you figure that? An ATX power supply will be much more conditioned than a cheap basic power supply.

Grab any 5 year or newer power supply and use the Graphics Connection.

It's a 4-pin connector with two +12VDC 15A a piece.

if its true to its label, then i guess it is usable even with the hotbed

The only problem I find with atx supplies, espeically cheaper ones is the voltage.

Im currently using a not so cheap 500w atx supply. It works great, but when the heated bed is on, the voltage drops to 10.8v - 11.0v. This limits the maximum temperature the heated bed can reach to about 90.

when i first built my printer, i also built one for a friend. we ordered two atx psu's. one cheap one and one corsair expensive one. i got the cheap one to "work" but even with the sense wire hooked up, a power resistor to load on the 5v and 3.3v lines, the voltage on the 12v line still dropped to around 10v with just the motors and hot end running. the second psu corsair psu would do the same thing, except when i turned on the heatbed it would just shut off. both of the psu's were rated for 500w and around 20 amps on the 12v rails. so for a while i delt with the crap atx psu with its fluctuating voltage, i hooked up an led light to it so i could watch the print and you could see when the motors started moving, and the heatbed turn on and off, the light would dim, it was ridiculous. oh did i forget to mention the heatbed would only get up to 93c with insulation and everything. so i finally looked on amazon and found a nice 12v regulated 30amp power supply and hooked it up. never had a problem since, and if i need a little boost it is adjustable up to 15v. also its very simple to hook up, no modification needed and most of the time fan does not even turn on, in fact if you dont have a heatbed the fan will probably never even turn on. and yes i checked the voltage when everything is running, its still 12. if you want i can run a print with my multimeter attached and record the voltage throughout the whole process.

and yes it regulates the power very well, when you need to run leds, even the slightest drop in voltage is easily detectable, espescially with rgb type leds as the blue and green need a higher voltage to operate.


[www.amazon.com]

Edited 1 time(s). Last edit at 05/02/2013 11:47AM by aduy.

Hi aduy, I have the same kind and must say I'm happy with it.

It's this one:
[www.ebay.co.uk]

i probably hack a 360 psu later on, but just to check the electronics ill use the psu for now

remember that a 250amp supply is only around 80% efficent. so take that 17amps available, and figure 3.4amps will be lost to heat!

I've just gone through the same thing upgrading my Prusa with a RAMPs controller and heated bed.

A 250W PC power supply such as the one shown in the pic should do fine.
That will provide up to a peak of 17A on the 12V rails which is enough for the motors, hot end and and a heated bed.

The trick these days is finding a PC power supply as SMALL as 250W!
I went to my local PC supplier and asked for the smallest cheapest PSU that had. It cost me $35, and it was a 550W supply. That was the smallest!

Sorry, need to revise my last post....

WATCH OUT FOR CHEAP ATX POWER SUPPLIES!

I've got load resistors on the 5v lines and the brown power ok line is hardwired to 3.3v by default.

Motors and extruder consume 2.18A.
Heated bed consumes 6.3A.

My new so-called 550W ATX PSU is supposedly rated to max 17A on the 12v lines and IT CAN'T HANDLE EVEN THE HEATED BED ON ITS OWN!

The 12V 120W (10A) step motor driver power supply I use on my CNC router handles the whole printer without cutting out at all.

I have an old 230 watt psu laying around here, and a new one with around 350 watt.

For my new ramps I will try to use the 350 one, so I have one 230 watt psu left over.. I'll sell it for 20 euros, ex postage. I live in Holland. But I think 230W might be a bit on the low side.

its ok i have a psu i aint going down the road with the atx psu im going hack a 360 psu, im just going to use the atx power unit to check my motors with my ramps when they arrive.

That's not how efficiencies are rated.

Power supplies are designed to deliver their rated current. The efficiency comes into play when calculating their draw.

jamesdanielv Wrote:
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> remember that a 250amp supply is only around 80%
> efficent. so take that 17amps available, and
> figure 3.4amps will be lost to heat!

chris33 Wrote:
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> its ok i have a psu i aint going down the road
> with the atx psu im going hack a 360 psu, im just
> going to use the atx power unit to check my motors
> with my ramps when they arrive.

360 PSU's work quite well. I built three printers with heated beds with them and they work great. No voltage sag (just make sure you get the 203 Watt version).

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Like he said get the 203 watt version of the Xbox psu. It puts out about 17a on the 12 v line. I have used 3 of these Xbox psu on 3 different builds and they work great even when running a 8x8 heated bed. Great power protection. I have a write up on how to hack them on my WordPress blog. Definitely put a switch between the red 5v line and the blue power sense line. Your at power supply says its 250w but its more like 204w and that's not including the power loss due to cheep cooling internally. These cheep power supply companies always inflate there wattage ratings.

I have yet to find an application that the Xbox psu doesn't perform well on. Its also very cheep to buy and will last a long time. The size and shape is also an advantage . I have mine tucked away. Another thing I recently did was de-solder the female psu connector off of a cheep broken Xbox motherboard to make all my connections smooth, organized and looking good. I swear by the Xbox psu's and will do so until I find something better. Happy building and good luck.

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yeah id love too run it from something like this Magnet generator creating a eco generator be the next step I reckon probably start make prototypes once my printers built

You know these magnet generators are all fake, don't you?

By the way, they don't output much power. It is so little you need one the size of an office building to generate enough amps. These machines are built around a concept of having minimal friction, but when you try to use them as a generator, they need more torque.

Pure 'Natural' (Neodymium) magnet engines will never exist. Free energy doesn't exist. It's math, it's science, it's mostly scams and fakes. Some machines may be 'near perpetual' mobiles (perpetual also doesn't exist) but they can't afford to output energy as it will cause too much friction and they will halt quite soon.





chris33 Wrote:
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> yeah id love too run it from something like this
> Magnet generator creating a eco generator be the
> next step I reckon probably start make prototypes
> once my printers built

you could just hook up a stepper motor to a bike, then pedal it, and voila you get a decent amount of current.

well people say that its fake but why cannot the concept work a dynamo generates elecric by coils in magnets

Becaue you lose as much energy on your way out of a magnetic field as you gain going into it. You cannot move a coil past a magnet and come out with more energy than it went in with. In a generator, you trade kinetic energy for electrical energy, and make up the kinetic energy by driving the input shaft.

In these perpetual motion machines, they purposely generate as little electicity as possible in order to allow the machine to spin under its own inertia for as long as possible, creating the illusion that its just one step away from being an unlimited energy source. Sometimes this is a case of the inventor fooling himself, lacking knowledge of thermodynamics and working by intuition its very easy to convince yourself your machine will work if only you can fine tune it. Many people spend years in the attempt. Other times its an outright con, the machine has a hidden energy store or input - a battery hidden inside, a mains cable under the table - that allows it to keep spinning and generating 'free' energy until someone has invested money into it, at which point everyone involved suddenly dissappears.

Edited 1 time(s). Last edit at 05/05/2013 07:06PM by Andrew Smith.

I'm not here to judge what he is making, just help out a fellow reprap person. besides craziness gets in the news more often.

I personally believe you never want to run something at its absolute spec limit all the time. but if a supply works then use it!

Edited 1 time(s). Last edit at 05/05/2013 10:03PM by jamesdanielv.

I recently hooked up an Antec Basiq 350W (23A on 12v rails). Drops from 12.1V to 11.5V when turning on the ~12A heated bed (nothing else running), hopefully should be alright for gen 6.

yeah after deciding to go down the 360 model i did find out what you mean make sure i get the right one, i only knew what you meant when i was trying to find a solution to hack the psu easier, so i decided to purchase the female connector on ebay and wire it from there so all i need to do is plug the power supply

Does anyone happen to know how to connect an ATX PSU to a Sanguino that only has a + and - and not an ATX connector? Or is it better to solder an ATX connector on the Sanguino? Does an ATX socket have any advantages over a normal + and - connection?

[web2.murraystate.edu] should help.

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