Question about 3d printer electronics, power supply

Hi
I am working on a 3d printer and I was wondering if the power supply I bought will power it?
I am using a MK2B12/24V Heat Bed, a Ramps 1.4 board from ultimachine, arduino mega, 4 nema17 stepper motors, and a Bowden All Metal hotend from Folger Technologies.
Here is a link to the hotend.
Folger Technologies Boden All Metal Hotend
It is a Reprap Rostock delta 3d printer.
I bought a 12v 20amp power supply.
Here is a link to the power supply
12VDC 20amp Power supply
I was just making sure everything will work for the printer before I hook it up.
Thanks
Tanner

Based on rated values, you may be good. Now if anything is out of spec from what they are suppose to be, then you may be under powered. It's not uncommon for a power supply to be overrated, and if your bed has lower that normal resistance (<1-1.2 ohms) then it will draw more than the normally expected 10 amps.

Let me know how that hot end works out. I have a peek jhead on mine. However I am on a quest to make all things metal on my printer. I have been looking at that hot end for a while wondering if it is truely 100% all metal. If it is, is the barrel polished or plainly just drilled. If its not polished properly it will jam. However you should be able to polish the barrel with a drill bit and some sand.

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Drill bit and sand? What exactly is that accomplishing?
Drill undersized and use a reamer

Edited 1 time(s). Last edit at 08/07/2014 04:02PM by flashnet.

I measured the resistance of the heat bed and it was 2.4 ohms, that is double the resistance of 1.2. That was between pins 1-3 and 1-2, the resistance was the same for both. Will the resistance go down when both 2 and 3 are connected to ground for the 12v setting?
If the power supply is to small what size of power supply do I need?
Thanks
Tanner

I had an almost identical setup on my Rostock.
Yes, it will power it, but not for long. Many rated specs for parts are actually a bit off and this goes double for cheap Chinese power supplies.

Bed, expect anywhere from 10-12amps
Motors, while they don't all pull max amps all the time, they can pull a full amp each, so 4-5 amps depending on the number of steppers.
Hot end, can pull 3.3 to 5 amps, like motors, this isn't a constant.
There is also some misc. power lost due to electronics and cooling fans (figure 1/3rd amp each).

It gets worse, your power supply, while rated at 20, may actually only be good for 16 under normal conditions.; The Chinese are either extremely optimistic or they use some unknown measurement known only to them, either way, it never does what they claim. Also remember, power supplies do not like running at full power. Bottom line, don't expect your cheap power supply to last more than a few months, I think mine lasted 3.


What I actually found I like best when I was using Ramps, was using a small 6 amp power brick for the electronics, and a separate 10amp brick for the bed. The bed power brick died after 8 months, but it was convenient in that I could leave it at home and still print PLA. They are also cheap and if one power supply failed, I could use the other and still print PLA. No down time. In your case, if you never transport your printer, buy a cheap power brick for the electronics and just use the 20amp for your bed. If you just want a single power supply, look into a 30 amp or convert a PC power supply that has 30 amps on the 12v line (important!).

Edited 1 time(s). Last edit at 08/09/2014 06:51PM by sheepdog43.

Quote
sheepdog43

What I actually found I like best when I was using Ramps, was using a small 6 amp power brick for the electronics, and a separate 10amp brick for the bed. The bed power brick died after 8 months, but it was convenient in that I could leave it at home and still print PLA. They are also cheap and if one power supply failed, I could use the other and still print PLA. No down time. In your case, if you never transport your printer, buy a cheap power brick for the electronics and just use the 20amp for your bed. If you just want a single power supply, look into a 30 amp or convert a PC power supply that has 30 amps on the 12v line (important!).

So to wire it this way should I connect the 20 amp power supply to the 11 amp input on the ramps and the small power supply to the 5amp input on the ramps, or is there something else I have to do?
Do you have pictures of how you have yours system hooked up?
Now the power supply I have has 2 outputs, does this mean 20 amps per output or 20 amp total draw?
Thanks
Tanner

That is 20amps peak. PSU's are rated in total wattage/amperage. Someone mentioned fires with these chinese units as well, be careful. To rehash the psu notion around here.

Here are some possible options.

XBOX 360 psu ~230w = 19amps on it cost 20-30 bux. And some hacking.
ATX psu ~ 250-1kv depending on the type, 20-350 bux and honestly not a good choice.
Chinese PSU 250-400w 20-60bux, however unknown standard and longevity, signal noise etc.
Name brand industrial psu ? not sure, never looked into them as they were out of my budget.


The option I used is none of the above. I got my hands on a used IBM server PSU, did some googling and hacked it to work. If I had bought the thing it would have cost me about 20-40bux used. Its rated for 1300w @ 220v input, and rated for about 650w at 120v. So either 54amps or something like 117amps at 220v. It does not care if the input source is not clean, it does not care if the input power is not stable, it will always put out 12.3v. It runs cool with the original fan and gives me enough room to add a secondary heater to my build and then some. I have enough amperage to accommodate two more printers on the same psu and it still would not sweat. Its built like a tank, its fairly efficient and for me it was 100% free. My buddy pulled it out of the recycling room at his job for me. Down side is that it is relatively loud, but no more than the printer is when its moving. I am happy with that.

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Quote
tanner331
So to wire it this way should I connect the 20 amp power supply to the 11 amp input on the ramps and the small power supply to the 5amp input on the ramps, or is there something else I have to do?

That's all there is to it.


On the PSU, the terminals are more than likely all wired together inside.

I bought a second power supply today, it is a dell 12v 16amp PC power supply, I got it from a local computer repair shop for $20. I decided to get this one because I could continue working on my printer today instead of waiting for a week for it to arrive by mail.
Tanner

I think you're asking for problems using two power supplies without isolating the 2nd one via a relay of some sorts.

Quote
cdru
I think you're asking for problems using two power supplies without isolating the 2nd one via a relay of some sorts.

The heated bed runs on a completely separate circuit than everything else. It's easy to run two power supplies like that on a Ramps board.

Actually RAMPS ties the grounds of both heatbed and main electronics inputs together, which is NOT ALWAYS 100% guaranteed to be safe or prudent.

If you're running two PSU's, always check there is no voltage difference between the grounds before connecting them to a board.

Quote
sheepdog43
The heated bed runs on a completely separate circuit than everything else. It's easy to run two power supplies like that on a Ramps board.

As Cefiar mentioned, the grounds are tied together. It can although not necessarily will cause issues with switching power supplies with the regulation circuitry. Now since the arduino has it's own power regulation and most of the remaining load is just resistive heaters, it's probably not a huge deal. But a automotive relay costing a buck or two at any automotive store removes any chance of issues.

I wouldn't run two power supplies anyways because I don't want to waste the space, or mess of wires, or have more things that have to be plugged in. Just wait the extra week for something to get mailed unless you absolutely positively have no other option.