I'm trying to run my Robo on 24v and I hit a snag.

3D Printing
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I’m trying to run my Robo on 24v and I hit a snag.

I got this power supply: http://www.ebay.com/itm/271395961709?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT and this step down converter: http://www.amazon.com/gp/product/B00BWKXTUU/ref=oh_details_o04_s03_i00?ie=UTF8&psc=1

I’m measuring 24 v on the power supply but I’m measuring 0v on the 12v line from the step down converter.

I’m stumped on what could be wrong. Any help?

Is it because this isn’t a buck converter but a step down?
http://www.ebay.com/itm/271395961709?_trksid=p2059210.m2749.l2649&ssPageName=STRK:MEBIDX:IT

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Make sure yup have a load, some supplies will not come up with no load. Minimum and Maximum current protection.

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I have a 12v light connected to the step down converter. Still not able to read a voltage or get the light on

4

Sorry out of ideas other than open it up and look for a blower internal fuse.

5

The 24v works fine and I can use it to heat the bed up. It’s just the converter that doesn’t seem to work

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Have you considered that the step-down (=buck in layman’s terms) converter could just be faulty?

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I thought most mobo electronics operated ok on 24v, with the exception of 12v fans. As long as the on board voltage regulators can handle the 24, and obviously your bed can handle it.

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Why not run everything on 24V? Turn down the max pid on the fans to half or run two in series.

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@Thomas_Sanladerer I’ve definitely considered that. I’m gonna see if I can find some other 24v sources to test it on, but I’m thinking the most obvious answer is probably the correct one. Just wanted to make sure I didn’t make some other mistake

@Eric_Moy @Brad_Hopper I thought about it but I just have too many things I want to run 12v on that it’s worth the effort to get it. You can technically run the ramps on 24v but I put in a polyfuse that’s only rated to 16v.

Thanks for the help all. I’ll go with the theory of a faulty step down.

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Did you read the comments on amazon? I’m affraid you bought a lemon.

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I did read the comments. Amazon agreed to a full refund so I’m going with this one instead: http://www.amazon.com/gp/product/B003P165NM/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1

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@Mike_Kelly_Mike_Make where are you going with this? Are you planning on just running the motors off of 24V or more?
Either way, it might be smarter to buy a separate 12V/20A power supply and tie the ground lines of both PSUs together. You’ll get much higher overall efficiency and save money up front as well.

These PSUs are fairly common as main power supplies for RepRap builds.

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@Thomas_Sanladerer I want to run my hbp off of 24v. On 12v I’m only getting around 120W of power which isn’t enough to maintain 100C.

So I want to run 24v line on a relay driven by the ramps board.

I want 12v because I have 3 fans, a light, and several LED strips that all run on 12v.

I have my stock 12v power supply but I was hoping to get everything to fit on the undercarriage of my robo. 2 power supplies won’t fit, which is why I’m trying to go with a step down.

For the intermittent I’ll run dual PSU’s until the new step down gets in.

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Well, that does look a bit better, but according to the comments, it does a very poor job on peak power. See the comment about the radio. So it would depend on what you plan to run on it.

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The Ramps board should be able to handle 24V, even for the bed. Maybe add a heatsink to the onboard FETs and limit the maximum PID output (P=U²/R, twice the voltage is four times the power). SSRs can cause their own set of problems.
Also, are you sure you need a 20A converter just for those parts? If you can make do with 3A, these are the converters i keep at hand and use practically everywhere: Lm2596 for sale | eBay

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@rein_stouten I’m planning on running 3 to 4 12v fans, a 20W 12v halogen, and several LED strips. Along with my stepper motors, and 2 cartridge heaters.

@Thomas_Sanladerer See the problem is I installed a 14A polyfuse: http://www.mouser.com/Search/ProductDetail.aspx?R=RGEF1400virtualkey65000000virtualkey650-RGEF1400 to try and run my heated bed normally on 12v. It’s unfortunately only rated at 16VDC. I can’t swap in the original 10A because that’s now on the 5A line after i cooked that one.

If I didn’t run the cartridge heaters on 12v I could probably use 3A. Though that’s pushing adequate power on the steppers.

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@Mike_Kelly_Mike_Make I wouldn’t. Not after reading the comments on Amazon. The fans and the 20W bulb and the halogen stuff, no problem, I think.
But to use this for the heated bed + cartridge heaters and the steppers as well, nah. Maybe if you put a large condensator over the 12V powersupply…But, as you already ordered it, let us know how it works out for you. I would certainly keep a close eye on the voltage when everything is running.

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@rein_stouten I won’t be running the heated bed on 12v, that will be on 24v. Pretty much the whole reason was to get the 400W from the bed instead of the measly 100W I got with 12v.

That amazon review only had 1 weird review and the guy was oddly specific. We’ll see though. I’m hoping it can at least do 120W which is why I went with this one instead of one rated at 120

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@Mike_Kelly_Mike_Make Okay, that does make a difference. Good luck.

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Spec on some of the caps is also 16 volts. Those babies pop like popcorn if they are overloaded. So watch out for that if you put 24 volts on the 5 amp side of the ramps power.