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Author Topic: Power supply - overheating
vdrome
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Post Power supply - overheating
on: August 15, 2014, 17:15
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Something that is beginning to concern me is how hot my wall-adapter is getting while running my Polargraph on Ramps 1.4. In fact I'm worried to run it for long periods of time because I can faintly smell electronic burning. It's a switching power-supply and I have it set to 12V and the machine runs smoothly. When turning it down to below 12V it doesn't do very much to resolve the heat issue, plus I noticed if I turn the adapter below 12v the motors start vibrating way too much.

Here's the adapter:
http://www.ebay.com/itm/UNIVERSAL-AC-DC-ADAPTER-ADAPTOR-SONY-1000mA-1-5-to-12-V-/221195412468?pt=LH_DefaultDomain_0&hash=item33804623f4

I'm not much of an electrician, but to me it's either a shitty power supply, or I need something with more juice. Any recommendations would be helpful!
sandy
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sandy
Post Re: Power supply - overheating
on: August 15, 2014, 22:55
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Ah that sweet smell of melting insulation. Yer it is a bit unnerving. It depends on your motors really, how much current they draw. In my experience, its quite unusual to find a stepper motor rated to draw less than 600mA, so that would require a 1200mA power supply for two. Now, the rating is for full power, and you never have both coils fully energised at once, which is why you can usually get away with supplying much less than that in practice.

I can't remember what kind of motors you had rigged up, but there is no problem with over-powering your machine. So don't be afraid of getting a 2A or more PSU. they new ones I'm using for the kits (which have the same motor drivers as RAMPS) are 2.6A (like this http://cpc.farnell.com/ideal-power/25hk-aj-090a266-cp-sa/international-psu-9v-2-66a/dp/PW02987), so there's plenty of headroom.

Sn
vdrome
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Post Re: Power supply - overheating
on: August 16, 2014, 04:51
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Hi Sandy,

Well, I'm using two motors rated at 350mA each from adafruit, don't know if that's a potential issue or not. Do you think I may need motors rated around 650-670mA? Maybe things are not running as smoothly as they could be, hmmm?

http://www.adafruit.com/product/324

And thanks for the heads up with the PSU, I'm going to rig up something of a better quality soon!
sandy
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sandy
Post Re: Power supply - overheating
on: August 17, 2014, 14:34
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Well both motors, fully on should only draw 700mA, which is well within the capability of an 1000mA supply. Are the motors getting hot?
vdrome
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Post Re: Power supply - overheating
on: August 17, 2014, 17:39
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No the motors are not really getting too hot at all. The PSU on the other hand is. The quality of the thing is pretty questionable. I think I should replace it.

And just to clarify, each motor should draw around 650-700mA? Or Both together should be drawing the same mA? Making the motors I have now, each rated at 350mA okay to use?

sandy
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sandy
Post Re: Power supply - overheating
on: August 17, 2014, 17:50
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What I mean is that if you have 350mA motors, then if they were both full on, they would draw 350mA each - so in total they would draw a maximum of 700mA together.

So you're asking your power supply to come up with 700mA of current, which seems very reasonable given it is a 1000mA supply. It _should_ be able to supply 1000mA.

It sounds like the PSU isn't that good. Another possibility is that it _will_ happily supply 1000mA, but only at a lower voltage (for a given power, current goes down as voltage goes up).

sn
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