Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Replacement power supply. Best way to wire up?
#1
So,

I have read the threads about the power supplies causing the "wobble" or banding on prints. I did some tests and proved with my printer that the original power supply does not cut it.

So I bought a new 300w power supply which is the same size and today it turned up. I opened up the printer and swapped out the power supplies, fired up the printer and started my test print. And I still got the banding!!!

I was a bit puzzled so looked at the specs for the power supply I purchased and then spotted the problem. It's a dual rail power supply, each rail supplying 15amps (The same as the original da vinci power supply). Now I am guessing that on the printer, the CPU power connector (Two yellow, two black) is the power for the heated bed and the hot end, does anyone know if this is correct?

My current plan is to cut one of the yellow wires and link it to the second 12v rail on the power supply, this will give the heated bed and the hot end their own individual power rails.

My other idea is to join the two power rails in parallel, this will give the added advantage that the bed would have access to 30amps and maybe heat up quicker (Not overly fussed about that).

So, has anyone else had this same problem and what did you do? Join the power rails or separate the hot end and heated bed.

Any advice would be greatly appreciated.

Thanks, Matt.
Reply
#2
yep Yellow=12V, Red=5V, Orange=3.3V,Black=0V

Note the lower connector also has Yellow as one of its 4 wires which almost certainly is shared with the other 2 cables so the actual board wiring is irrelevant if you are plugging in the lower connector as well. If you are using a PC power supply unfortunately the positions of the wires don't match the layout of the +4 part of the connectors so an adaptor is needed (While I'm at it I would wire up an adaptor to join your two black/yellow rails together - I prefer not to cut wires if possible).

If you're using the same style of power supply you can just plug it in but yes I would tie the two rails together for the top (if that is inadequate you'd need to join them to the lower 12V wire also, but I seriously doubt that is necessary).

I have been investigating the power supply (which is definitely dodgy). I measured power consumption and noticed basically 4 levels

9W - Plugged into wall but switched off at machine
26W - Switched on idle
56W - Running extruder and motors
159W - Running extruder, motors and heating bed

So the figures they have quoted don't seem to match reality: Unit is alledgedly 2A @ 240V => 480W, but only uses 1/3 that. Heated bed is rated at 130W but only uses 103 suggesting that it may be choking for power. Max power output is listed as 200W with lower voltages listed as 75W max. Assuming a standard 20W heater cartridge leaves only ~100 for the heated bed.
Reply
#3
Well I've wired it up but still having no luck. I don't know if i'm just wiring it wrong.

I have the 4 pin connector, two yellow and two black. I have cut one yellow and one black of this wire and joined them to one yellow and one black from the main ATX connector (I believe that one rail on the PSU is for the CPU and the other rail is for the motherboard).

After doing the above I did a continuity test and all three 12volt rails and all three grounds are linked to each other (Before I did this, the lower plug 12v was not linked to the upper plug 12v). In my head this must mean that both the 12v rails on the PSU are now linked??

Unfortunately my multimeter is only rated for 10amps so I cannot see how much current is being drawn. But I have done a test print and I'm still getting the banding. I'm sure the power supply is the issue because if I disable the heated bed my prints come out perfect.

I don't know what to do now. Is there any other wiring method I can try? It's either that or get yet another power supply but this time take note of the 12v supply rail Sad. I have found a 400 watt power supply with a 25amp 12v rail, but its slightly bigger than the standard one. http://www.ebay.co.uk/itm/Single-1U-400W...19fd70fb64

Whats sort of power do I need on the 12v rail? the standard psu is 15amp max,

Thanks, Matt.
Reply
#4
Rails are for peripherals and graphics card: CPU doesn't use 12V and motherboard itself use very little. You'll need to connect a yellow and black line from each of the lines that supply the hard drives to the graphics card connector.

As for total power requirement worst case scenario would be with 12V 1.8 steppers, 40W heating element and 130W bed = 21.4A
Reply
#5
The 4 pin connector (two yellow, two black) is the CPU connector. On bigger PC power supplies they alaso have the PCI E power connectors for peripherals such as graphics cards etc.

According to the ATX specification the CPU power connector will be attached to one rail and everything else on the second rail. This is to prevent the CPU form being starved of power.

Anyway just to rule everything out I have just tested linking all of the 12v cables together and an equal number of ground wires from both rails and I am still getting the same problem. I guess this power supply isn't any more powerful on the 12v rail that the current one Sad.

Think I wil try with an external PC ATX supply I have kicking around and just make sure it is going to make a difference before spending any more money. What would be nice is if they shipped the printer with a decent power supply in the first place!!

Matt.
Reply
#6
I just used a standard single rail ATX using an adaptor as mentioned previously and let me just say when the unit is receiving adequate power you will see and hear the difference. I haven't printed anything big enough to really check the banding issue, but the machine runs much smoother.

Definitely worth the effort.
Reply
#7
Do you know how many amps your power supply gives on the 12v rail?

I have just found another psu that gives 17amps on the 12v in comparison to the 15 on the standard one and on my dual rail one.

I saw in another thread someone using a 320watt psu which also supplied 17amps so I think it should be OK

Matt.
Reply
#8
Mine is 32 Amps on the 12. Total power consumption has gone up I'm guessing about 4A, though I'm using a high efficiency power supply so output power could be somewhat higher and thats just an estimate. A high quality 17A might do the job but a standard one might not, if you have it lying around its worth trying, but if you were buying one especially I'd go 400W+
Reply
#9
I assume your running that as an external psu? Ideally I want to keep mine internal so am limited the the flex type itx psu.

I've ordered this 17amp one, if it still doesn't do the job then I may have to go external. My other thought was using a 12v led strip power supply and a couple of voltage regulators for the 5v and 3.3v. Those power supplies are cheap and have lots of power. My reprap ran off one and I never had any issues. Shame they didn't go that route on the printer and have the voltage regulators on the board.
Reply
#10
yeah mine is external. If you're using the smaller ones maybe you could squeeze it into the case with the original and wire them in parallel if extra power is needed? Might have some ventilation issues though. I prefer to not damage/mod the original panels so I was going to print up a custom enclosure for the back and screw it into position with the original panel screws. Also wouldn't mind getting some airflow over the stepper drivers and putting heatsinks on them so a cooling fan might be in order.
Reply


Forum Jump:


Users browsing this thread: 1 Guest(s)