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Forum Index : Other Stuff : 3 amp Constant Current PS for CNC
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Bryan1 Guru  Joined: 22/02/2006 Location: AustraliaPosts: 1343 |
Hiya Guys, Below is a schematic for a 3 amp constant current power supply for powering a stepper for cnc use. I've tested it on the cnc i'm making and using my nife bank as the power supply. Input voltage 12.8 volts Output voltage when the stepper is at rest 4.8 volts The voltage ramps up as the stepper speed increases and using the above input voltage the running speed @ 8foot/minute was 11.8 volts. 
Not many components and it does work perfect. Have fun guys Cheers Bryan 
Edit: Thanks for the tip Glenn |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Nice work Bryan. A constant current source is a must have for fast reliable stepper operation. I see the forum has resized the picture down a little to far. Its gone for the default 500pixels wide for JPG images. If you save the screen shot as a GIF file before uploading it, the forum will only resize down to 1000pixels wide, better for circuits and plans etc. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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vasi Guru Joined: 23/03/2007 Location: RomaniaPosts: 1697 |
Interesting source. How you power the steppers? With or without current limiting? 12V steppers? Hobbit name: Togo Toadfoot of Frogmorton Elvish name: Mablung Miriel Beyound Arduino Lang |
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| woodchips Newbie  Joined: 05/01/2009 Location: United KingdomPosts: 27 |
Bryan C1 is the wrong way round, what about for C2 and C3? Bob |
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| Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1343 |
If you know electronics then you will know some schematic software will do things different. The concept of that schematic is to show a simple way to get a 3 amp CCS. To pick by the way a schematic is drawn is plain out there behind the out house and your in the sh*te pile before ya know it To Vasi, This CCS will only draw the current needed for the stepper and be limited to 3 amps so current limiting resistores aren''t needed. |
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GWatPE Senior Member  Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hey Bryan, I am with U on this. Far better to present something. Those who know a bit will put the caps in the right way round anyway. Gordon. become more energy aware |
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| woodchips Newbie Joined: 05/01/2009 Location: United KingdomPosts: 27 |
Bryan Yes, I do know electronics, I was rather more concerned with the majority who don't, and want a correct, working circuit to follow. I can also read data sheets, where the catch diode must have a current rating at least 1.3 times the output current, so the 3A 1N5822 isn't really up to it. Does it need the feedforward capacitor, if not then why not? Someone without the detailed electronic knowledge, or suitable test equipment, could be in for a long session of headscratching. When you only have limited experience you both need and want to know why? Why is this a good circuit? Why is it better than a variable three terminal regulator wired as a constant current source? And Bryan, it takes no more time to do the job correctly than incorrectly, and those that don't know have an exploded capacitor in their face, rather on your consciences than mine. Bob |
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