How are you powering your printer?

How are you powering your printer?

I’m in the market for a new power supply for my printer. The ATX supply I scrounged from a bin at my hacker space just isn’t up to the task. New ATX supplies seem so cheap, but it seems silly to pay for the 5v and 3.3v capacity I’ll never use.

Is there a cost effective way to get a 12v-only supply with the capacity I need?

Or should I just buy an ATX supply and get on with life? Any brand names I should look for or avoid?

I use ATX because I have a bunch sitting around.

Don’t believe the claimed ratings, even on the better ones.

I looked into that and could not find a cheaper alternative. Looking farther down the road if you later want to add Raspberry Pi and and Octoprint /webcam the power you need will be there ! The tech here is developing daily and denying that option for a few dollar saving [if possible] makes little sense.

I’ve got a surplus place around me + my hackerspace so lots to choose from. I’m running a 6A pour that’s smaller than the power brick for an xbox. By the way, xbox supplies make great psus as well.

I use a 12V 30A power supply that I got off ebay. It’s more than enough power and has been working great for almost a year now. Something like this:

same as Kevin 12 volt 30 amp from ebay. I’ve bought 3 of them. No problems.

This type of power supply is really nice:

If you look around (ebay has a good selection, mostly direct from China), you can find a fanless (silent) 250W version that should be more than sufficient.

I like the idea of something I can get from Amazon, since I have some gift cards to spend.

@Whosa_whatsis Those supplies from Amazon are tempting, but they have pretty mixed reviews. To be fair, the cheap ATX supplies have rather mixed reviews too.

@William_Frick You have a good point. I do have plans to hook up a RasberryPi to my printer some day.

That depends on what platform heater you’re using and its resistance (W = V^2 / R). BTW, I’ve seen a bit of evidence that running your platform heater with enough voltage to heat it quickly will compromise its dimensional stability. Creating uneven layer heights. When the heater turns on, it will quickly get hot in the center and bow up, and the bowing will decrease as the temperature equalizes. Slower heating will minimize these dimensional changes in the platform.

@ThantiK How do you run a printer on only 6 amps? I need more than that just from my steppers. Adding the extruder and print bed doubles my draw.

@Jim_Wygralak I have a 110v heater pad that’s switched via a 5v solid state relay. The entire heater bed basically draws nothing from my power supply and draws directly from mains.

I plan on getting a 110v cart heater for the hot end as well, and eventually swapping the whole thing down to a 3-4A PSU. The solid state relays I’m running are also quite a bit beefier than they need to be.

Well that’s just cheating, Anthony. I’m running the whole shebang on 12V. 4 steppers @ 2A ea. Extruder @ 3A and bed @ 10A

@Jim_Wygralak Your steppers might be rated for 2A or 3A, but the drivers won’t draw that amount of current from 12V. All common drivers are “chopper” drivers, essentially a step-down current mode regulator that efficiently transforms 12V into the ~2.5V the stepper needs. So the driver will only draw about 400mA from 12V for each stepper in normal use, totaling in about 1.6A needed from the supply.

Personally, i used a Scythe 650W 80+ silver ATX supply. It provides enough power for a second heated bed and was on sale when i got it. It works pretty nicely, powering the Ramps/Arduino and a RasPi from 5VSB (which provides power as long as the PSU’s main switch is on) and has the Ramps switching it on once a print is started.
For ATX PSUs, i’d recommend anything that has an 80+ label. Not only does this guarantee a sufficient efficiency, but also that the PSU is no firecracker so cheaply made that it will release its magic smoke the first time the heated bed turns on.

@Thomas_Sanladerer chopping stepper drivers don’t run the motors at those low voltages. The motors are still running at 12v, it’s just that the current is brought down so the total power stays the same. So while they’re 2A at 4V (8 watts), they’d be around 0.66A @ 12V, maintaining 8 watts to stay in the capacity of the motor. This is also the rating “per phase”, so 1.2A, being that bipolar motors have 2 phases. (edit: to clarify, theoretical max, if both phases were powered…which basically never happens)

@ThantiK Ohm’s law does still apply, which does not allow the motor itself to draw that little current at 12V (a 2A 4V motor would draw 6A at 12V). For the driver/motor combo seen as one unit, your math is correct.

Yeah, that’s what the chopper drivers do. They WOULD draw 6A if they were allowed, since we’re running them at 12v. The drivers we use have current limiting pots on them which allow us to drop the amount of current running through them. They are running at 12V. We constrain them within their rated wattage, run them at higher voltages, and reduce the amount of current that goes to them. This allows the inductive coils of the stepper motor to reach charge significantly quicker, allows us to operate faster, also allows microstepping, etc.

Throw a multimeter on your coils sometime. They run at 12v.

Oh, i missed that last paragraph about phases: It does not matter that there are two, since they will never be fully energized at the same time. Full steps go:
Phase 1 Current / Phase 2 current
100% / 0%
0% / 100%
-100% / 0%
0% / -100%
or something like that. Every stepper driver datasheet has huge tables disclosing the currents for each microstep.
But basically, a 2A motor will never get more than 2A total from the driver (if set up correctly)

Yeah, fully aware of that. You’ll never have both phases fully powered. As the PWM of one phase drops, the other will rise. Edited the phrase to clarify.

I’m actually wondering why we aren’t running these at higher voltages (24v, specifically)

@ThantiK i threw an oscilloscope at my coils once -
In the second picture, under all the spikes, you’ll see the basic sine wave that drives the motor. It is ±2V.
But i think i know what our disagreement is here: I’m talking about RMS, you’re saying peak-to-peak. In the end, we’re both right.

But still, why should i use 24V for a 2-ish V stepper?