Electronics > Beginners
Multiple Output Power Supplies
Rapsey:
I have a 3D printer which has been acting up lately. Every few hours it randomly crash-reboots during operation. This is proving quite difficult to debug so I figure I should try a process of elimination. The way I see it the two prime suspects are: a fault in the main board, or an unstable power supply. So if I can run the printer from a different power supply I should be able to rule that one out.
The printer's power supply is your typical 12V/30A switching mode power supply unit. It has 3 outputs and the printer uses all 3 of the positive terminals and 2 of the negative ones.
I wouldn't be drawing anywhere near 30A since most of that goes towards powering the heaters and I can reproduce this fault without using those. But as it happens I do have one other power supply which is also rated for 12V/30A: a dual output Turnigy power supply which is typically used for powering RC LiPo chargers.
Since the Turnigy PSU only has a two outputs I would need to pair 2 of the printer's positive wires together. So now the question is: is this a safe thing to try? I know in simple circuits you can just share a power rail but I'm not sure what the implications are for more complex devices. The printer is essentially an Arduino with a bunch of FET's, fans, stepper motors, temperature sensors (resistors) and two heating elements (also resistors) which I won't be using in my tests.
Arznei:
There shouldn't be any problem with that. The three outputs of the printers power supply are most certainly internally connected anyways.
CatalinaWOW:
They are already paired internally in your existing supply, so I wouldn't expect any problems from that. Other possible problems would be noise or voltage regulation. Your Turnigy supply is designed to charge batteries which don't really care about a few volts of ripple. Not likely to be a problem. If you have any kind of DVM you can at least roughly evaluate this. Couple the supply to your meter through a capacitor and compare the AC voltage you see from both supplies. If the Turnigy is not greatly larger than your original supply it is probably fine.
Rapsey:
Great, thanks! I'll give it a go.
--- Quote from: CatalinaWOW on February 24, 2019, 07:10:57 pm ---Other possible problems would be noise or voltage regulation. Your Turnigy supply is designed to charge batteries which don't really care about a few volts of ripple. Not likely to be a problem. If you have any kind of DVM you can at least roughly evaluate this. Couple the supply to your meter through a capacitor and compare the AC voltage you see from both supplies. If the Turnigy is not greatly larger than your original supply it is probably fine.
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I suppose I can just use an oscilloscope to check the ripple. Why would you connect the meter through a capacitor? Wouldn't that smoothen out the ripple you're trying to detect?
rstofer:
--- Quote from: Rapsey on February 24, 2019, 07:56:55 pm ---Great, thanks! I'll give it a go.
--- Quote from: CatalinaWOW on February 24, 2019, 07:10:57 pm ---Other possible problems would be noise or voltage regulation. Your Turnigy supply is designed to charge batteries which don't really care about a few volts of ripple. Not likely to be a problem. If you have any kind of DVM you can at least roughly evaluate this. Couple the supply to your meter through a capacitor and compare the AC voltage you see from both supplies. If the Turnigy is not greatly larger than your original supply it is probably fine.
--- End quote ---
I suppose I can just use an oscilloscope to check the ripple. Why would you connect the meter through a capacitor? Wouldn't that smoothen out the ripple you're trying to detect?
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To force the meter to only see the AC ripple, not the DC value. It's often hard to see a small number when it's masked by a bigger number. You can use a lower scale to measure just the ripple.
Some DMMs do this when you select ACV but it's hit and miss when there is a large DC component.
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