- JohnParticipantMay 23, 2016 at 7:47 amPost count: 17
I am not done yet but I wanted to post an update pic.
I am doing a 30×30 build in PETG. There are a couple of ABS parts in the corner pieces that I printed when I ran out of PETG but nothing pivotal.
Electronics as follows:
Motors: recommended NEMA 17s
Boards: ramps 1.4 with LCD both in printed enclosures (I still need to get a fan for the ramps board)
Power: PC power supply putting out 50 amps on the 12 volt rail at I think around 80 to 90 percent efficiency. Its a Roswell so pretty good efficiency. I do not remember the exact numbers since its been a couple of years. (I know that its a serious overkill but I happened to have it around so it was free)
Tool: I have an Rotozip around that I plan to use for now. I hope it works out because I have never found anything good to do with it before this. It is not quite the beast that the Dewalt is but its what I already have.
Everything is pretty standard so far. I have a MDF top for it. I need to build out the frame but that can be done in an hour or so. I have printed up the rest of the center and feet as well it is not pictured here though.
The build has been relatively smooth so far. I had to re-print a lot of pieces because I had a setting off in S3d. Once I corrected that, everything fit together great.
Once I am done with the table, the power supply and ramps will be under the table while the LCD will sit on top with the MPCNC. It should be much cleaner looking.
Attachments:vicious1KeymasterMay 23, 2016 at 10:59 amPost count: 2642
So far so good. I have tried 3 different computer power supplies and only 1 has worked so far. I am not sure what the difference between them was but they all had plenty of power but if you get random brown outs on your machine it’s the power supply. The one that does work is nice because I use it’s fan to cool the ramps as well. I want to do something alone the lines of the table in the “coffee with the MPCNC” video for my power supply and board an all that, nice tool mount holder space and everything.JohnParticipantMay 23, 2016 at 12:09 pmPost count: 17
That is interesting to know. I am not an electrical engineer but I assume there is a lot going on with PC power supplies due to all the voltage outputs. Might cause things to flow less consistently and cause those power drops that you described. This is a pretty good PS but that might not make a difference for this purpose. I guess I will see how it works out. Worst case scenario is that I just have to get a new PS. they are not terribly expensive.
FyleoParticipantMay 23, 2016 at 1:09 pmPost count: 4
- This reply was modified 5 months ago by John.
usually for old power supply, you need to put some load on the 5v rail to be able to get full power on 12v rail.
It’s less true with recent power supply where the regulation mecanisme is based on 12v instead of 5v.vicious1KeymasterMay 23, 2016 at 1:11 pmPost count: 2642
Awww really?! I threw them out thinking they were bad! Bummer. Thanks for the info.FyleoParticipantMay 23, 2016 at 1:14 pmPost count: 4
Miss the load part.
I load mine with a 5ohm 50W resistor between the 5v and ground. (1A load)JohnParticipantMay 29, 2016 at 4:45 pmPost count: 17
99.5 percent done. Just gotta extend out these stepper cables a bit.
Attachments:vicious1KeymasterMay 29, 2016 at 4:55 pmPost count: 2642
I’m rebuilding my other machine with all the new updates. I have made an absolute mess of my work space. I can’t wait to get back to the point your at.JohnParticipantMay 29, 2016 at 5:48 pmPost count: 17
Yea, I will probably print the new middle in a month or so. For now, I just want to get it running, learn some of the software and cut some stuff out.JohnParticipantJune 2, 2016 at 11:39 amPost count: 17
So I wanted to provide an update on the power supply. My PC power supply worked fine until I tried to actually run a gcode. once I tried to do a dry run, it shut off. After doing that, I hooked up a left over 100kom resistor to the 5v rail of the power supply and a ground since I had this left over. This did not resolve the problem. I did a little research and found that if the resistor is too large then it will not draw enough amperage hit that constant draw requirement to keep the PS on. As a test, I hooked up a case fan up to the 5v rail and ground. Doing this took care of the problem. The power supply now runs like a champ.
Summary: if you run of a PC power supply and having issues, then make sure that you are pulling enough amps from the 5v rail. Smaller resistors are better here.
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